Glass industry	mg/Nm3		Direct discharger g/m3	Sample type	Indirect discharger3) g/m3
Dust Sulphur dioxide as SO2 Glass melting furnaces Pot furnaces and day tanks NOx nitrous oxide as NO2 Fluorides Chlorine Filterable solids Total suspended solids Chemical oxygen demand Antimony Arsenic Lead Cadmium Chromium Cobalt CyanideS2) Copper Manganese Nickel Palladium Platinum Mercury Rhodium Selenium Tellurium Thallium Vanadium Zinc Tin	SO2 NOx F CI TSS COD Sb As Pb Cd Cr Co -CN Cu Mn Ni Pd Pt Hg Rh Se Te TI V Zn Sn	50 1800 1100 400-3500 5 30 5 1 5 0.20 5 1 5 5 5 1 5 5 5 0.20 1 1 5 0.20 5	100 0.50 80 0.50 0.07 0.10 0.10 0.10 0.10 2.00	1) 2) 2) 2) 2) 2) 2) 2) 2)	50 1 1 2 0.50 2 0.20 2 3 0.05

*	May be formed in reduced burning	COD	Chemical Oxygen Demand
**	Law applicable in the German state of Baden-Wberg	TSS TA-Luft	Total Suspended Solids Technical Instructions on Air Quality Control
1)	Two hour mixed sample	VwV	Administrative Regulation
2)	Random sample	WHG	Federal Water Act

Glass works, which are generally large-scale plants, produce considerable emissions. In principle a maximum of 1800 mg SO2Nm3 should be established as the mean guideline value for avoiding serious environmental pollution. The NOx emissions must not exceed the currently applicable values, and nitrate refining should be dispensed with because of the high NOx levels generated.

No separate wet or dry sorption plants are required to comply with these relatively high mean values. Accurate control of the tank heating is vital in order to attain the required values.

Fluorine and chlorine emissions which may give rise to direct damage must be kept as low as possible. The values indicated above can be achieved by suitable selection of raw materials and fuels and systematic monitoring of burner operation. A further benefit is that energy consumption can be further reduced by conforming to these guideline values, resulting in greater economy.

The dust emission from glass furnaces should not exceed 50 mg/Nm3. A dedusting plant should always be installed in order to comply with this limit.

It is vital to adhere to the emission limits for toxic dusts (heavy metals) such as cadmium, lead, fluorine, selenium and arsenic; the maximum values specified in TA-Luft must not be exceeded.

For individual substances, the Compendium of Environmental Standards contains notes on evaluating environmental relevance.

It is absolutely essential to comply with the regulations on permissible noise levels, since failure to prevent or protect against noise can result in permanent injury of employees.

To avoid environmental pollution, the limits laid down for direct water dischargers must be observed, particularly regarding heavy metal concentrations in the effluent.

If no national regulations exist, values in line with German or European standards should be established for the erection of new glass works, particularly in areas already suffering from serious environmental pollution. Special regulations must be introduced for plants already in operation. The parameters defined for the principal hazardous substances must in future be regularly monitored and disclosed by the glass works, so that appropriate steps can be taken immediately in the event of nonconformance (see 3.1).

For all practical purposes it may be assumed that in order to comply with the limits indicated all alkali borosilicate, borate, lead and most special glass furnaces must be equipped with dedusting systems. Allowance must be made for these dedusting and sorption systems as early as the planning phase.

In countries with low-cost electricity it is possible to construct glass furnaces of special design which produce far lower emissions and do not require expensive environmental protection equipment. The energy requirement per kg of glass can also be reduced by introducing such melting methods.

3.1 Inspection and maintenance of environmental protection installations

A control centre independent of the production process must be established to comply with existing environmental protection regulations. The responsible personnel must be enabled to perform and monitor all inspection functions including measurements relating to environmental protection in the works. They should be available for consultation on investments and take charge of negotiations with environmental protection authorities. Moreover, this department is responsible for ensuring that all environmental protection installations are regularly maintained and upgraded. This internal environmental department is also responsible for staff training.

4. Interaction with other sectors

Glass works which rely on numerous secondary operations, such as workshops, compressed air generation, fuel stores, galvanisation shops, refining shops, transport and packing departments etc. are also affected by regulations applicable in other sectors.

Because of the relatively high transport costs, container glass factories must be located near their main customers. Modern sheet glass works, on the other hand, can only operate economically with capacities upwards of 600 t/day, thus they supply their products to more distant sales areas and are reliant on good transport facilities.

Table 5 - Environmental impacts of adjacent sectors - Glass -

Interacting sectors	Nature of intensification of impact	Environmental briefs
Extraction/storage of raw materials and fuels	-Landscape impairment - Pollution of bodies of water - Waste storage in former pits	Planning of Locations for Trade and Industry Urban Water Supply Rural Water Supply
Disposal of solid and liquid waste	- Discharge of deposited solids e.g. filter dusts - Pollution of bodies of water by wastewaters	Solid Waste Disposal Disposal of Hazardous Waste
Maintenance of workshops and transport facilities	- Risks of handling water pollutants (e.g. solvents) - Impacts of transport and traffic (noise, link roads)	Mechanical Engineering, Workshops Road Building and Maintenance Planning of Locations for Trade and Industry

5. Summary assessment of environmental relevance

The effects of glass works on the environment and workplace are caused by noise, dust, effluent and flue gases.

Table 6 - Environmental impact of process stages (glass)

Process	Air		Noise	Water	Soil	Work- place
	Waste gas/ Flue gas	Dust1)
Dressing Melting Moulding Cooling Sorting Packing Machining/Refining	1 3 2 2 1 1 1	2 3 1 1 1 1 2	2 3 4 3 2 2 2	1 3 2 1 1 1 3	2 3 3 2 1 1 1	2 3 4 2 1 1 2

Key: 1 very slight; 2 slight; 3 moderate; 4 considerable

In some cases technological and processing developments and improvements have already been implemented, e.g.:

- Arsenic and tellurium are now only used as refining agents in exceptional cases.
- Fluorspar is no longer used as a flux.
- The specific outputs of the tanks have been increased with a simultaneous reduction in energy consumption.
- Wastewater circuits have been introduced.
- Numerous noise protection devices have been installed.
- Wet, electric and dry sorption plants have been installed for dust extraction.
- Tank designs and fire management systems have been improved.

Many of the processes so far tested in individual cases are capable of further technical improvement and more economic design, paying particular attention to environmental regulations. The expected costs of environmental protection devices and measures may be as much as 20% of the total investment costs of a glass works.

Proper maintenance is essential to environmentally acceptable operation of the plants. Suitable training must be given and personnel generally made aware of environmental concerns.

Early involvement of neighbouring population groups in the planning and decision-making processes will enable measures to be devised to deal with any problems arising.

In countries which have no legal guidelines it should be ascertained as early as the planning stage, based on the raw materials to be used and the process technology applied, what environmental protection measures are necessary and appropriate. Environmental protection equipment provided should be of robust design so that the life of this equipment is appropriate to the overall project and so that simple, low-cost maintenance can be guaranteed.

6. References

Allgemeine Vewaltungsvorschriften enehmigungsbede Anlagen nach § 16 der Gewerbeordnung 1985.

Allgemeine Verwaltungsvorschrift indestanforderungen an das Einleiten von Abwasser in Gewer - 41. AB-Wasser VwV, 1984.

Betriebswacht, Datenjahresbuch 1991, Berufsgenossenschaft der keramischen und Glas-Industrie, Wg.

1. Bundesimmissionsgesetz (BImSchG), 1985.

Entwurf zur Abwasserverordnung: Deutscher Industrie- und Handelstag, Anhang 17, Sept. 21, 1990.

Glass Manufacturing, Effluent Guidelines, World Bank, August 1983.

Guidelines of the Bundesministerium des Inneren [German Federal Ministry of the Interior] regarding the BImSchG, directives of the Council of the European Community.

TA-Luft: Erste Allgemeine Verwaltungsvorschrift zum Bundes-Immissionsgesetz, GMBR 1986 (A).

Siebzehnte Verordnung zur Durchf des Bundes-Immissionsschutzgesetzes 1990 (Verordnung erbrennungsanlagen fe und liche brennbare Stoffe, 17. BImSchV).

Barklage-Hilgefort H.J.: Minderung der NOx-Emission durch feuerungstechnische Maahmen, Glastechnische Berichte 58, Nr. 12, 1985.

Bauer H.D., Mayer Dr. P.: Zusammenf staubmeechnischer Daten und arbeitsmedizinischer Befunde am Beispiel von Asbesteinwirkungen, Sonderdruck aus "Der Kompa 91, Nr. 7 1981.

Bundesverband des Deutschen Flachglashandels e.V., Glasfibel, Vertrieb Kelasa GmbH Cologne, 1983.

Doyle T.J.: Glassmaking Today, An Introduction to Current Practice in Glass Manufacture, Portcullis Press, Redhill, 1979.

Fer H., Feck G.: In Vitro - Studien an kchen Mineralfasern, Sonderdruck, Zbl. Arbeitsmed. Bd. 35, Nr. 5, 1985.

Gebhardt F., Carduck E. und Arnolds J.: Chloremissionen von Glasschmelzwannen, Glastechnische Berichte 51, Aachen 1978.

Gilbert G.: Zur Ausbreitung von Schadstoffen, insbesondere von Stickoxiden in der Atmosph, Glastechnische Berichte 51, Aachen 1978.

Kircher U.: Emissionen von Glasschmelz - Heutiger Stand, Glastechnische Berichte 58, Frankfurt 1985.

Markgraf A.: Abgasentstaubung hinter Glasschmelz mit filternden Abscheidern und vorgeschalteter Sorptionsstufe zur Beseitigung von HF und HCI, Glastechnische Berichte 58, Nr. 12, Stadthaben, 1985.

Mayer P., Bergass: Grenzwerte fest am Arbeitsplatz und in der Umwelt unter besonderer Berhtigung der keramischen und Glas-Industrie, Sprechsaal 2/80, 1980.

Mayer P., Bergass: Glasfaserste und ihr gesundheitlicher Einfluauf den Menschen, Sonderdruck der Zeitschrift, Die Berufsgenossenschaften e.V., Bonn.

Schaller K.H., Weltle D., Schile R., Weissflog S., Mayer P. und Valentin H.: Pilotstudie zur Quantifizierung der Bleieinwirkung in der keramischen und Glas-Industrie, Sonderdruck Zbl. Arbeitmed. Bd 31, Nr. 11, 1981.

Tiessler H.: Zum Einsatz eines Elektro-Entstaubers an einer Spezialglaswanne fali-Borosilikatglas, Glastechnische Berichte 51, Nr. 7, 1978.

Winterhoff G.: Abgasentstaubung periodisch arbeitender Glasschmelz, Glastechnische Berichte 58, Nr. 12, 1985.

1. Scope

This environmental brief covers iron and steel production and processing with the following activities:

- sinter, pellet and sponge-iron production
- pig iron, cast iron and crude steel production (including continuous or strand casting)
- steel forming (hot and cold)
- foundry and forging operations.

The above activities are carried out in an integrated ironworks or sometimes in separate locations.

After delivery and pretreatment of the ore in the ore preparation, sintering and where applicable pelletising plant, pig iron is smelted in the blast furnace with the addition of coke and admixtures; coke supplies the energy and reduces the ore to pig iron. In the converting mill the molten pig iron is refined to form crude steel by top blowing or purging with oxygen and the addition of scrap. Crude steel is also produced from scrap in electric furnaces, sometimes with the addition of pig iron, ore and lime. The crude steel is either continuously cast as blanks or, after casting as slab ingots or blocks in permanent moulds, rolled in the hot rolling mill to form sheets, billets or profiles. Further processing takes place in the cold rolling mills and forges. Continuous casting which already represents 90% of German and 60% of worldwide steel production improves crude steel utilisation by some 10%, saves energy by rolling operations and reduces the production scrap yield in steel and rolling mills per tonne of finished steel by more than 50%.

The direct-reduction process represents an alternative to traditional steel production. With the addition of reduction gas, e.g. from natural gas or coal, sponge iron is produced as a solid, porous product from which crude steel is then refined in the electric furnace, often with the addition of scrap. 90% of sponge iron is produced by the gas-reduction process.

Cast iron smelting takes place in the cupola furnace, with increasing use of induction furnaces.

Moulds and cores are required for the shaped casting of cast iron; these are mostly of sand but frequently contain an organic binding agent.

The following are classified as major units:

sintering plants 20,000 t/day
blast furnaces 12,500 t/day
steel converters 400 t holding capacity
electric furnaces (arc) 250 t holding capacity
cupola furnaces 70 t/h
induction furnaces 30 t/h

In many countries steel is extensively produced from scrap in electric furnaces.

Since iron and steel production is predominantly based on pyrometallurgical processes, air pollution is a primary consideration. In addition to a multitude of gaseous air impurities, dusts play a special role, not only because they occur in large quantities but also due to the fact that the dusts contain some hazardous substances affecting both man and the environment, e.g. heavy metals. Due to the use of coolant water and wet separation methods, problems of maintaining water purity also occur. Continuous casting plants require high specific water quantities from which the wastewater is considerably contaminated with oil. Casting without spray-water cooling relieves the load on water resources.

Metallurgical processes also produce slags which should be recycled wherever possible. Where no effective recycling and final dumping facilities exist, dusts and sludges separated from the waste gas cleaning systems represent potential pollutants of the ground and water environments.

In blast furnace plants and converting mills, also in rolling mills and forging works, noise and vibration protection is of fundamental importance. Foundries produce large amounts of waste from used sand, broken cores and cupola slag.

For reasons of ecology and economy, work is taking place worldwide on process methods which permit the use of coal instead of coke and the extensive use of lump ore instead of sinter or pellets. This would enable coking and sintering plants to be dispensed with as emission sources in a metallurgical plant.

Other developments concern the casting of rolling feed stock in approximately final dimension form. Shortening the process chain permits reductions in energy requirements, residual substances, waste and emissions.

2. Environmental impacts and protective measures

2.1 Sintering / pelletising plants

Sintering plants form lumps of fine ore prior to introduction into the blast furnace and recycling of ferriferous residues (waste materials). Sintering is the traditional method of treating residual and waste materials from the smelting plant. Factors determining the limits include the zinc concentration, because zinc in the sinter contributes in the blast furnace to the formation of scaffolding with impaired gas distribution.

Sintering plants produce the following emissions:

Waste gases and dust containing components with potential environmental relevance:

SO2, NOx, CO2, HF, HCl, As, Pb, Cd, Cu, Hg, Tl, Zn

Of dust components, the heavy metals lead, cadmium, mercury, arsenic and thallium have the greatest environmental relevance where these are present in the charge materials. The relevance of anthropogenic heavy metal emissions is based less on their overall emission rate than in high localised mass flow densities or concentrations. The iron and steel industries are among those industries in whose vicinity the highest immission rates of heavy metals occur in the air and ground.

Dust is separated and returned to the sinter process in gas cleaning systems, normally electrostatic precipitators. In continuous operation the dust content of clean gas is between 75 and 100 mg/m3. Heavy metal, e.g. lead, enrichment in the sinter plant dust is possible with continuous recycling. Dust with heavy concentrations of lead and zinc should be conducted to a zinc and lead recovery system. In the case of stoppages of the sintering belt due to faults, care must be taken to ensure that the gas cleaning system continues to operate at maximum possible separation capacity. In addition to sintering belt dedusting, modern sintering plants also have room dedusting whereby dust-laden waste air from transfer stations, chutes, crushers etc. is cleaned by a hot sieve system.

Depending on the composition of charge materials, inorganic gaseous fluoride and chloride compounds as well as sulphur dioxide and nitrous oxides are emitted. Sulphur dioxide emission can be significantly reduced by using coke with a low sulphur content. The emission of gaseous pollutants can also be reduced by increased lime dosing. This results in problem substances being transferred to the separated dust. Where regional conditions and process engineering do not permit these measures, wet-process desulphurisation systems offer a means of reduction; in this case some problem substances are transferred to the wastewater. On account of the large gas volumes - up to 10 E 6 m3/h - only partial waste gas desulphurisation can take place. For this reason preference should be given to primary measures. Concentrations in cleaned waste gas are around 500 mg/m3 sulphur dioxide.

With respect to noise impact, a distinction is made between the noise immissions of operations to the neighbourhood and the effect on the staff at their work-places. Principal noise sources of the sintering plant include the large fans for drawing air through the sinter cakes, cooling the sinter and dedusting. Crushing and screening stations should be housed in solidly constructed buildings whose walls restrict the propagation of sound. Possible noise reduction measures are silencers in the air supply and discharge pipelines, also the encapsulation of individual units. The acoustic power immission level is used to evaluate the noise radiated to the open air by the plant. The acoustic power level of a noise source is a distance-dependent parameter; for sintering plants without silencers on supply and discharge air pipelines it can be as high as 133 dB(A) and for those with silencers 124 dB(A). With very good acoustic planning and execution an immission level of around 40 dB(A) can be achieved at a distance of 1,000 m from the individual noise sources. If this target cannot be achieved, protection of the residential area adjacent to the sintering plant is only possible by noise protection measures on the propagation path, e.g. a noise abatement wall. Measures for optimising noise protection are to be considered in parallel with the planning of the production unit.

By encapsulation and the separate installation of principal noise sources it is also possible to protect the work places. The typical noise level in the sintering hall is between 83 and 90 dB(A); attention must be paid to the use of personal noise protection because long-term exposure to an acoustic power level in excess of 85 dB(A) results in serious hearing impairment. The wearing of safety helmets and shoes also helps reduce industrial accidents. Staff in work-places particularly exposed to dust, gases, noise and heat are to have regular preventive medical examinations by works doctors.

In pelletising plants, fine ores are mixed with additives and water to form green pellets which are burned in pellet incinerators on travelling grates. The dust-laden waste gases are cleaned in dedusting plants, usually electrostatic precipitators. The filter dust is re-used. Pelletising plants are associated with lower dust and gas emissions than sintering plants. In contrast to sintering, pelletising is mainly performed at the ore mine.

2.2 Blast furnaces

The blast furnace is a countercurrent reactor loaded or charged from the top with layers of feed and coke, the molten pig iron and slag being drawn off from below. Hot air is injected in the opposite direction from the bottom of the furnace. Residual materials (waste) such as oily metal chips and oily rolling scale can be introduced after sintering.

The principal emissions, residues and waste materials are:

- top gas, with the following potentially environmentally relevant components: CO, CO2, SO2, NOx, H2S, HCN, CH4, As, Cd, Hg, Pb, Ti, Zn
- top gas dust (dry) from the gas cleaning plant with high iron contents (35 - 50%)
- slag with the following major components: SiO2, Al2O3, CaO, MgO
- sludge from the waste gas cleaning system
- wastewater from the waste gas cleaning system, with the pollutants: cyanides, phenols, ammonia
- dust from the casting house dedusting system.

The waste gases from the blast furnace are pretreated in mass force separators (dust catchers or cyclones) and, in a second stage, finally cleaned with a high pressure scrubber or wet electrostatic precipitators. Clean gas dust concentrations from 1 to 10 mg/m3 are achieved.

Other dust emissions in the blast furnace area, particular from the burdening process, pig iron desulphurisation and the casting house must also be identified and cleaned.

Dust formation ("brown fume") in the casting house affects not only the neighbourhood but also, to a considerable extent, the workplaces. Efficient casting house dedusting systems which intercept process waste gases and peripheral emissions at the taphole, runners and cut-off points and separate dusts in horizontal electrostatic precipitators can achieve clean gas dust concentrations significantly under 50 mg/m3 (best values 7 and 12 mg/m3 and dust emission factors between 0.020 and 0.028 kg/t pig iron in blast furnace plants with a capacity of 4,000 to 6,000 t/day). As a replacement for the standard collection and cleaning methods, trials are currently in progress with the suppression of "brown fume" through inertisation with nitrogen.

In the dedusting of pig iron desulphurisation, clean gas dust concentrations of 50 mg/m3 are adhered to in both calcium carbide and soda desulphurisation, using radial flow scrubbers or electrostatic precipitators.

The top gas contains between 10 and 30, though possibly as much as 60 g/m3 dust with 35 to 50% iron, i.e. 30 to 80 kg/t pig iron, in older plants 50 to 130 kg/t pig iron. The dust is separated in the dry state in mostly multistage separators, from where it goes to the sintering plant and from there back to the blast furnace.

In view of the zinc and lead content and other factors, the top gas scrubbing water sludge must be disposed of by dumping, unless there is a special hydro-cyclone separation system. With higher concentrations, it should be transferred to a non-ferrous metal works. Recycling in this way would leave the blast furnace process practically free of residues. Dumping involves the risk of leaching and hence penetration of the soil and groundwater by compounds of zinc, lead and other heavy metals. The dump must be permanently and verifiably sealed and the seepage water must be collected and chemically processed. The special requirements imposed on such a dump must be laid down in the project planning stage.

Slag produced by the blast furnace process accounts for roughly 50% of the overall waste materials from pig iron and steel production. This slag is mostly used in road-building. Part of the molten slag is granulated by quenching in water. This so-called slag sand is also used in road-building. Part is used to produce iron slag Portland cement and blast furnace cement. Quenching and granulating releases carbon monoxide and hydrogen sulphide. The wastewater has an alkaline reaction and contains small quantities of sulphide.

Slag heaps sometimes produce seepage water with high levels of dissolved sulphides and strong alkaline reaction, posing a hazard for the groundwater. Slag heaps must be sealed and any seepage water must be treated.

Wastewater is generated by top gas scrubbing and simultaneous wet dedusting. The wastewater is normally clarified in settling tanks and, where necessary, gravel bed filters and recirculated. The wastewater contains suspended matter (dust) and sulphides, cyanides, phenols, ammonia and other substances in dissolved form. The last three substances must be removed from the wastewater using appropriate physical and chemical treatment processes.

The top gas can be used as a fuel for heating purposes within the works, in view of its high carbon monoxide content due to the reducing atmosphere in the blast furnace, though this will inevitably result in the formation of carbon dioxide, with its climatic implications.

Excessive levels of sulphur dioxide and nitrous oxide gases can be reduced by flue gas desulphurisation and denitrification.

Carbon monoxide concentrations in the workplace pose a particular problem. Where top gas pipes are not perfectly leakproof there is a danger of poisoning with possible fatal consequences for workers present at the furnace throat. Close attention must also be paid to CO concentrations by carrying out measurements and ensuring that protective breathing equipment is worn during repair and maintenance work on shut-down blast furnaces or gas cleaning systems.

Protective equipment for blast furnace workers includes fireproof clothing, breathing equipment and ear protectors, depending on where they are working; protective helmets and safety footwear must be worn in all areas.

Noise in blast furnace plants comes mainly from the combustion air fans and the charging process; also there is the noise generated upon changeover from blast to heating operation. Suitable abatement measures include silencers, enclosure of the furnace throat or encapsulation of all valves and shields. The noise level from the blast furnace plant is in the range of 110 to 125 dB(A); the level of background noise in the immediate vicinity may be 75 to 80 dB(A). Possible noise reduction measures should be selected as early as the blast furnace planning phase. Their effect can be determined by advance calculation, taking care to ascertain the significance of the emission sources (plant sections and operating processes). One should preferably begin by damping or eliminating occurrences and noise sources which arise only periodically.

2.3 Direct-reduction plants

Direct reduction plants function according to a variety of methods, e.g. with shaft furnaces or rotary tube furnaces which are similar to blast furnaces. In the former, the top gas is scrubbed and then enriched with natural gas and used for heating; in the latter, the gas is not used unless steel and rolling mills are available for this purpose. If this is the case, the gas should be burnt provided the CO content is sufficiently high. The waste gas flow is cleaned by mass force separators (dust chambers) for preliminary separation and then by fabric filters. Sulphur dioxide emissions may occur in the solids reduction process, depending on the sulphur content of the coal used.

2.4 Crude steel production

Excessive carbon content impeding further processing of the pig iron and substances influencing the quality of crude steel, such as silicon, phosphorus or sulphur, are either expelled in gaseous form or slagged during the steel production. The following emissions occur in the steel works:

- waste gases and dust containing components with potential environmental relevance: CO, NOx, SO2, F, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Si, Tl, V, Zn ammonia, phenol, hydrogen sulphide and cyanide compounds may occur, depending on the process.
- dust from waste gas cleaning
- slag

In the steel works dust is formed mainly due to the top-blowing or through-blowing with oxygen necessary for oxidation. The solids content of the waste gases from the oxygen converter is between 5 and 50 g/m3. They contain finely dispersed evaporation products of iron oxides and primary anoxide ("brown fume"); also sulphur and phosphorous compounds, fluorine compounds and, where fluxing agent is used, silicon tetrafluoride.

Specific dust masses are approximately as follows:

- electric furnace: 2 - 5 kg dust per tonne crude steel
- bottom blowing converter oxygen bottom metallurgy (OBM) 5 - 10 kg dust per tonne crude steel
- top blowing converter (LD and LDAC process) 15 - 20 kg dust per tonne crude steel

Gases occurring in addition to carbon monoxide include inorganic fluorine compounds with the addition of fluorspar, also small quantities of sulphur dioxide and nitrous oxides, nitrous oxide formation being significantly higher in electric furnaces than in the blowing converter.

A technical solution exists for the collection and cleaning of the process gases from the converter. A fixed or lowerable hood over the converter prevents the intake of large quantities of infiltrated air or the escape of converter gases. The gas is subsequently dedusted by a wet or dry process. Wet dedusting takes place in a two-stage operation by a combined wet scrubber and wet electrostatic precipitator. For dry dedusting, dry electrostatic precipitators are used, designed to resist internal pressures up to 2 bar (due to risk of deflagration). The clean gas concentrations are under 50 mg/m3 dust and under 500 mg/m3 sulphur dioxide. A value of under 400 mg/m3 nitrous oxide cannot be continuously maintained. Maintenance of the separation equipment is important in order to achieve an adequate continuous level of separation. Dry dedusting is advantageous as the yielded dust can be returned to the converter after hot briquetting.

Transfer, charging and mixing processes produce random dust emissions which may pose a considerable nuisance for the neighbourhood. Clean gas contents of 10 mg/m3 can be maintained by a waste gas collection system with a collection rate of 90% and a downstream separator using fabric filters or horizontal electrostatic precipitators.

Proposals for the use of a process-dependent control and instrumentation system for reducing specific waste gas quantities must be examined with respect to system requirements such as robustness, error detection ability and ease of maintenance.

Since waste gas collection is difficult with Siemens-Martin furnaces while the furnace is in operation, the solution is to convert to electric furnaces. In addition to lead and zinc, chromium, nickel and vanadium occur in the dust if electric furnaces are used to produce fine steels. Certain chromium compounds in the form of breathable dusts have proved to be carcinogenic.

A full doghouse enclosure is necessary to achieve 95% collection of the waste gases occurring with electric furnaces during charging, smelting and casting. Fabric filters permitting clean gas dust concentrations of under 20 mg/m3 are used for dust separation.

When the converter is in operation, large amounts of carbon monoxide are produced which should be transferred for controlled burning in a torch or in a boiler with energy conversion, so as to avoid excessive air burdens (immissions). A potential source of polyhalogenated dibenzodioxin and furan emissions (though not currently thought to pose a major risk) is the recycling of iron scrap in electric steelmaking plants. Large quantities of iron scrap contaminated with halogen compounds and the operating conditions give rise to the formation of these substances. Initial random sample checks yielded emission concentrations of the order of a few nanograms. A comprehensive measuring programme is being prepared. Careful selection and preliminary sorting of iron scrap is currently a practicable way of minimising carcinogenic emissions. Processes for separating health-endangering dioxins and furans are currently being developed. Current trials of activated charcoal adsorption filters and their separation capabilities are being followed with close interest.

The wastewater from wet dedusting is clarified in a hydrocyclone or settling tank and recirculated. The separated sludge is dewatered by a vacuum drum filter and returned to the blast furnace via the sintering plant. Attention must be paid to the zinc content of the sludge upon recycling. Slag produced in steel works is used in road construction or processed into fertilisers.

Loud noise is generated in converting steel works by high-powered fans and dedusting systems and in electric furnaces by the arcing and transformer. Noise levels in electric steelmaking plants without noise reduction measures is between 117 and 132 dB(A), and around 100 dB(A) with noise reduction.

Noise reduction measures can include:

- arc soundproofing
- smaller apertures in the furnace shell
- encapsulation of the furnace
- acoustic separation of the furnace bay from adjacent bays
- increasing the soundproofing of bay walls
- silencers on air intakes and outlets
- slow-running cooling air fans
- enclosure of individual systems
- avoiding free-fall of scrap upon loading and charging.

Very high peak noise levels can occur during smelting, especially with wet scrap. Highly automated modern plants have control rooms which provide effective protection against noise at the workplace. The protective measures mentioned under 2.2 also apply to workplaces in steelworks.

2.5 Steel forming

The following emissions and residues occur with forming (shaping) of crude steel into rolled steel:

- oily rolling scale
- waste gases from the furnace
- oily wastewater
- wastewater from the waste gas cleaning

During the production of steel plate, the following are produced:

- oily wastewater
- waste air from the pickling baths
- spent pickling solutions
- sulphuric and hydrochloric acid
- or nitric and hydrofluoric acids
- mixtures

The most prolific residue produced in hot rolling mills is rolling scale. The specific mass is 20 to 70 kg/t finished steel. Scale comprises mainly iron oxides (70 - 75) and can therefore be utilised in the blast furnace. Finer components must first be sintered or pelletised. Oily scale with a small percentage of oil from the machinery lubricants can be freed of oil by combustion or by alkaline wet scrubbing. To avoid polluting the subsoil with oil, oily scale should not be dumped.

Wastewater is produced in the hot rolling mill by

- transport of the scale to the wastewater treatment system
- alkaline washing of the oily scale.

The scale-water mixture is separated in settling tanks and gravel filters (sometimes with the addition of flocculation agents). Floating rolling oil and grease is skimmed off and the settled or filtered scale is dewatered and transferred to the sintering plant. The clarified wastewater is recirculated.

The alkaline scrubbing water from the scale scrubber contains an oil emulsion which must be broken down with chemicals. The water contains oil and chemical residues. It should be transferred to a biological filter plant. The recovered oil can be processed and in certain cases re-utilised in the rolling mill.

In the cold rolling mill the steel plate is descaled in a pickling bath before further processing. Hence, no solid waste (scale) is produced in the actual cold rolling process.

With cold rolling, wastewater occurs due to contamination of water with rolling oils (mineral oils, palm oil) and from the pickling. The rolled down plates are once more pickled with acid and electrolytically degreased prior to tinning or galvanising.

Wastewater treatment requirements in rolling mills depend on the type and extent of recycling and the quality of the receiving body of water. Regular monitoring of wastewater values is necessary.

The oil-water emulsions produced by the cold rolling process must be chemically treated (flocculation with ferrous salt and lime). The oily sludge must be incinerated and the ashes transferred to the sintering plant. Oil separated from the emulsion can be used for secondary lubrication purposes.

To protect soil and groundwater from unwanted discharges, a waste disposal and re-utilisation record should always be kept for emulsions, mixtures of mineral oil products and mineral oil sludges.

Spent steel pickling agents contain mainly ferrous salts. These can be separated and sold (for production of pigments, precipitation agents for clarification processes, sulphuric acid). The remaining pickling agent must be neutralised with lime milk. The resulting hydroxide sludges are placed in drying beds or preferably dewatered with filter presses. Before dumping, the leachability and stability of these residues must be checked to ensure they are suitable for final dumping. If the solids content exceeds 40%, the residues should be taken to the sintering plant.

The acid pickling water must be neutralised and the coagulated hydroxide sludges separated in clarifying tanks. The clarified wastewater can be re-used (must be neutralised with acid); sludges must be placed in a suitable, sealed dump.

Special hoods are used to eliminate oil mist in rolling mills; it is separated by a mechanical preliminary separator combined with a downstream electrostatic precipitator.

The effective noise level generated by hot and cold rolling mills is 95 - 110 dB(A). In a rolling mill the noise level, e.g. 5 metres from the open bar steel train, is 106 dB(A) and in a pipe steel rolling mill, near the tube straightening machine, as much as 124 dB(A).

To protect workplaces from noise, the plant is extensively automated and provided with appropriate control rooms. These can be well insulated against noise. Ear protection should be worn at workplaces with high levels of noise.

2.6 Foundry and forging operations

Smelting takes place in cupola furnaces (shaft furnaces) and electric melting furnaces. Gaseous emissions from smelting are: carbon monoxide, sulphur dioxide, fluorine compounds and nitrous oxides; those from casting are: phenol (briefly), ammonia, amines, cyanide compounds and aromatic hydrocarbons (traces).

Dust occurs in foundries during e.g. preparation of the moulding sand and core sand, manufacture of sand moulds and cores, in casting, cooling of castings, knocking out moulds and with the surface treatment of parts of moulds, known as fettling. Fabric filters have proved effective for reducing dust emissions. These have permitted the achievement of concentrations of under 10 mg/m3 in the clean gas from sand preparation dedusting systems. Optimum fine dust separation with fabric filters can help reduce toxic emissions, e.g. nickel, during fettling.

Dust occurring in cupola furnaces during smelting is intercepted by wet type dedusters or filtering separators. With cold blast cupola furnaces with smelting capacities below 10 t/h, wet dedusters are increasingly being replaced by fabric filters with preliminary separators. Clean gas dust concentrations of under 20 mg/m3 are being adhered to. Fluorine emissions can also be reduced by dry absorption using hydrated lime.

It is essential to intercept emissions in all operating phases, including blowing and melting-down.

With hot blast cupola furnaces with smelting capacities exceeding 10 t/h, operators have managed to obtain clean gas dust concentrations of 20 mg/m3, with blowing and melting-down as well, using optimised wet type dedusters in combination with primary measures on the cupola furnace. An enclosed forehearth feed bay also contributes to low-emission operation.

The use of induction crucible furnaces is increasing; with these, emissions from the crucible opening are intercepted by an extraction system.

When using electric furnaces, which produce significantly lower dust emissions than cupola furnaces, values of 20 mg/m3 are possible using filtering separators. Additional emissions of hydrochloric acids, soot and traces of organic compounds (possibly dioxins) occur when smelting large amounts of scrap mixed with oil, paints and plastics. A high-performance wet scrubber must be used under these operating conditions.

Highly odorous substances such as formaldehyde, phenols and ammonia occur in foundries for small castings for which moulds are produced according to the cold-box, hot-box or Croning process. In addition to the odour nuisance, these substances are also health hazards. As formaldehyde and high ammonia concentrations are suspected carcinogens, steps must be taken to reduce these. Emissions can be reduced by a counter-current scrubber with a phosphoric acid solution. The scrubbing fluid is recirculated and continuously treated.

Waste gases with inorganic compounds occur during core production, including core sand mixing. The waste gases must be cleaned with a wet scrubber and in particular the amount of amines in the waste gas must be under 5 mg/m3.

The sludge-water mixture resulting from wet dedusting, which may contain substances hazardous to health and the environment such as cadmium, lead and zinc, is neutralised. The precipitated solids are separated from the water by sedimentation. The scrubbing water is recirculated. Before dumping the sediment, which may contain phenols from the moulding sand binders, it must be tested for leachability and treated if necessary. In a suitably modified process, part of the wastewater flow can be evaporated and the circuit largely, closed, thereby considerably reducing the scrubbing water requirement.

The moulds are made of moulding sands with approx. 4 to 10% binder (clays, cement, organic materials, hardenable plastics, soda, water glass etc.). They are usually used once and then broken up. The used sands can be treated and re-used as components in clay-bonded mould production.

The ambient noise levels in foundries can reach 120 dB(A). Noise sources include loading operations, mixing, dedusting systems, fettling bays, sand preparation, conveyors and fans. Noise reduction measures include enclosed hall designs, installation of fans in enclosed rooms and silencers on air intakes and outlets. Machine soundproofing measures are especially necessary in the moulding, core and fettling shops. Measurements made over an 8 hour shift have yielded workplace noise levels of 106 dB(A) in the moulding shop, 99 dB(A) in the core shop and 103 dB(A) in the fettling shop. Principal noise sources affecting workplaces are: jolt moulding machines, vibratory grates, swing conveyors, fettling machines, impact pneumatic tools, grinders, fans, compressors and conveyors.

Appropriate noise protection measures in the workplace include encapsulation of noisy machines, separation of noisy machines from other parts of the shop and avoidance of manually operated machines. Personal ear protection must of course be worn. Monitoring is imperative.

Waste gases are expelled from the furnace in forges. Emissions can be controlled by using gas as a fuel. A forge must be regarded as an industrial installation as regards production of wastewater and waste materials.

The ambient noise level in a forging shop with e.g. 6 hammers (impact energy 0.6 to 1.3 Mpm) is 112 dB(A). The background noise level due to heating furnaces, fans etc. is already 90 to 100 dB(A); to this must be added the pulsating noise of the forging machinery. Forging hammers are louder than mechanical and hydraulic presses. It is important to maintain a safe distance between the forge and purely residential areas. This distance must be calculated and allowed for in the planning where a reasonable noise level cannot be achieved in the near vicinity through noise reduction measures in the works. The maximum noise level in the workplace of a drop hammer (1,500 kg tup weight) is 120 dB(A). That of an electric forging hammer in the workplace (tup weight 275 kg) is 97 dB(A). The interior noise level in forging shops is normally above 90 dB(A).

Possible noise reduction measures include reducing structure-borne noise by modifying the forging force curve, reducing the propagation of the structure-borne noise, encapsulating work room openings, reducing the noise from pneumatic control systems, placing silencers on air relief pipelines and using multiple tube nozzles for descaling. The wearing of personal ear defenders should be obligatory and should be monitored.

Besides noise, forging also produces vibrations. Measures to reduce vibration include the definition, at the planning stage, of suitable foundation designs, with appropriate vibration insulation at the time of installation. Vibrations in the neighbourhood must be below the threshold of perceptibility.

3. Notes on the analysis and evaluation of environmental impacts

Emissions produced by the iron and steel industry require particularly extensive measures and systems for air protection. Above all, dusts containing substances hazardous to health and the environment, such as lead, cadmium, mercury, arsenic and thallium, must be cleaned by high-performance separation systems. Nowadays, not only the primary emission sources, such as sintering plants, but also secondary sources such as blast furnace casting bays can be intercepted and dedusted. In the case of gaseous emissions, attention must be paid primarily to reducing carbon monoxide and sulphur dioxide, as well as nitrous oxides and fluorine compounds.

Monitoring of permissible emissions and the effectiveness of waste gas cleaning systems must be guaranteed by measurements. The dust must also be periodically analysed to detect heavy metals. Emissions must be measured after commissioning the plant to see whether the values assumed in the planning correspond to the reality. If there are discrepancies, new forecasts must be made and further reduction measures implemented if necessary.

Emission and immission standards applicable in Germany are detailed in TA-Luft (Technical Instructions on Air Quality Control) and in the Groeuerungsanlagenverordnung (Ordinance on Large Firing Installations). In the USA, guidelines and standards for the iron and steel industry have been published by the Environmental Protection Agency.

The guidelines adopted by the Association of German Engineers (VDI) contain detailed descriptions for performing emission and immission measurements. Measuring equipment designed for continuous operation must be rigorously examined for robustness, error detection ability and ease of maintenance. Maintenance contracts should be concluded with suppliers. Continuously operating measuring instruments should be employed for measuring dust, sulphur dioxide, fluorine compounds and nitrous oxides (e.g. in the sintering plant and the steel works).

Recycling of water and the use of closed-circuit cooling water systems deliver cost-savings and a high rate of re-use in iron and steel works. Effective water treatment systems are needed for this purpose.

General minimum requirements are laid down in Germany for treated wastewater discharged into receiving bodies of water and for special plants. These parameters must be monitored by measuring equipment at the point of transfer of the cleaned water to the receiving body of water. Cleaning systems for waste gases and water can only satisfy their intended purpose when they are correctly operated, serviced and repaired. The provision of detailed operating, maintenance and repair manuals is imperative.

Practically all processes involve greater or lesser levels of noise. High noise emissions can cause annoyance in the vicinity if reduction and protection measures are inadequate. In Germany, TA-L (Technical Instructions on Noise Abatement) and the guidelines adopted by the Association of German Engineers (VDI) are used for calculating and assessing noise immissions in the neighbourhood. Noise immissions are assessed against immission reference values which are graded according to the type of area to be protected and the periods of noise. Guidelines are also available for assessing noise emissions at the workplace.

As in Germany, works environmental protection officers should be deployed in iron and steel works who are totally independent of the production side. Their task is essentially to work towards the development and introduction of environment-friendly processes. In addition they are entitled and obliged to monitor adherence to statutory regulations and compliance with official directives and conditions in so far as these relate to environmental protection.

The scope and monitoring of working conditions and health protection measures, which vary from one workplace to another, should be set down in a manual. Proposals are detailed in the regulations of the employers' liability insurance association (Berufsgenossenschaft) of the iron & steel industry. Suitably qualified safety officers and a works doctor should be appointed.

4. Interactions with other sectors

The erecting of iron and steel production plants involves land-use which is measured in terms of the works site with adjoining areas and connecting roads. Before erecting production plants, impacts on the local natural order and the geogenic and anthropogenic burdens on the soil and groundwater and on any bodies of surface water must be investigated in the context of the location planning. An adequate distance from the nearest residential zones must also be guaranteed. Details are contained in the environmental brief Planning of Locations for Trade & Industry.

Iron and steel works involve large-scale production and require large amounts of raw materials. These include primarily ores, coke and limestone. Generally speaking, to produce 1 tonne of crude steel requires 450 to 500 kg coke and fuel oil, 250 kg lime and 5 m3 water.

In an integrated iron works for example, the specific total energy consumption is some 20 GJ/t crude steel. In an integrated iron works, the sintering plant, blast furnace, coking plant, steel works, rolling mill and power station areas are interconnected as a combined energy system. Thus, the top gas is utilised in all areas, its calorific value enriched with converter gas, coking oven gas or natural gas. Power and steam are supplied by the power station. Boilers are usually operated with gas, e.g. top gas. The burners can be fired with top gas, coking oven gas or fuel oil. External power supplies are used in addition to internally generated power. Waste heat boilers from the steel works contribute to steam production.

A mixed iron works is linked to the following other sectors:

- The raw materials (ores, coal, limestone) must be mined in large quantities in open cast or deep mines. (See environmental briefs Surface Mining and Underground Mining).
- Ores must be dressed (see environmental brief Minerals - Handling and Processing).
- Efficient transport routes (canals, railways or roads) are required for transporting raw materials and products. For environmental protection reasons, transport should mainly be via inland waterways and railways. Whether the location of the iron works is chosen because of where the ore, coal or sales market is situated, high-capacity transport facilities must always be provided.
- Coke of specified quality must be supplied for the blast furnace by a coking plant. Reference should be made to the environmental brief Coking Plants, Coal to-gas Plants, Gas Production and Distribution to assess the environmental impacts associated with coke production.
- In view of the quantities of cooling water needed, an adequate water supply must be available. To avoid the adverse consequences of drawing excessive quantities of water from groundwater or surface water resources, extensive recirculation systems must be provided, internal treatment of wastewater and cooling water. Water consumption must be in harmony with the general water framwork planning.
- The large workforce of a mixed iron works may result in the disorganised development of housing at an insufficient distance from the plant. This can lead to water shortages, unsatisfactory wastewater treatment and disorganised dumps, plus immission burdens affecting the areas of habitation.
- Other sectors directly or indirectly linked to the iron and steel industry are: lime kiln plants, cement works, ferroalloy production plants, power generating plants and slag and dust recycling plants. The above plants and establishments are associated with considerable potential atmospheric burdens. Reference is made to the relevant briefs.
- A general or single-purpose dump is to be provided for non-recyclable residual and waste materials including furnace debris from the metallurgical processes with hazardous pollutants. These should be classified according to criteria of environmentally acceptable final storage (see environmental brief Disposal of Hazardous Waste).

5. Summary assessment of environment relevance

The establishment of iron and steel production plants in areas not previously used for industry will have an impact on the landscape. Environmental damage can be reduced by selecting locations with relatively insensitive landscapes where there is unlikely to be any great effect on the regional productiveness of the natural environment.

The environmental burdens imposed by an iron and steel making plant and related technologies relate to the air, water, soil, flora and fauna, waste, noise and vibration.

Efficient separators are available for reducing dust emissions. Important in this regard is the continuous monitoring of the operation of these separators using suitable measuring equipment. Since a large proportion of the separated dust can be re-utilised in the process, high-performance gas cleaning systems are desirable, not only for environmental protection reasons but also in the interests of economy. Increasing attention is being paid to random dust sources, e.g. from working bays. Tried and tested collection systems are available for this purpose. High dust immissions occur in the vicinity of iron works. Although high grade cleaning of waste gases reduces dust emissions, dust emissions for the iron works as a whole are between 1 and 3 kg/t, depending on the number of installed process stages and the extent of dust reduction from diffuse sources. 1 kg/t should be regarded as an optimum value. Studies should be carried out in all cases to determine whether agriculture in the vicinity of the works is being impaired by contamination over wide areas with phytotoxic and zootoxic heavy metals, especially zinc, copper, chromium, nickel and lead, taking into account long-term deposition and accumulation in the soil. Heavy metals, especially cadmium and mercury, can be injurious to human health through accumulation in the soil and in plants, with increased absorption through the food chain. Conflicts can be avoided or diminished by consulting the affected population groups at an early stage, possibly developing and planning new sources of employment (see also Vol. III, Compendium of Environmental Standards).

As the increased environmental burden poses additional health risks and hazards, e.g. for women and children (during pregnancy etc.), adequate medical care should be provided in the project region.

In some respects air protection measures lead to a shifting of problems, e.g. where separated residues cannot be recycled. A high degree of recycling of the material and energy present in dusts, sludges and gases is a basic requirement for environmental compatibility, and one that can be met. For materials which cannot be recycled, a dumping system must be selected which will enable environmentally acceptable final dumping.

Although technological development in iron works has led to high water consumption, use of water in the plants can be minimised by recycling as much as 80% and through the use of closed cooling circuits. The standards applicable to the cleaning of wastewater contaminated with heavy metals must be raised from the level of the general rules previously applicable in Germany to a truly "state-of-the-art" level.

Noise levels can be minimised by extensive noise reduction measures. However it is also important to ensure an adequate distance between the works site and neighbouring areas of habitation.

Possible ways of preventing adverse environmental impacts through state-of-the-art emission reductions in old plants include (in the process engineering area) replacing old converter techniques for steel production with low-emission converters and electric furnaces and introducing continuous casting in approximately final dimension form. In the waste gas and air purification area, the use of multistage separators, fine dust separators and the interception of diffuse emission sources is also possible in old plants. Increased recycling of residues and water will help reduce the environmental burdens imposed by old plants. Secondary noise reduction measures are more difficult to implement than primary measures.

6. References

Statutory provisions, regulations

Erste Allgemeine Verwaltungsvorschrift zum Bundes-Immissionsschutzgesetz (Technische Anleitung zur Reinhaltung der Luft - TA-Luft) dated 27.02.1986, GMBl (joint ministerial circular). 1986, Ausgabe p, S.95.

Zweite Allgemeine Verwaltungsvorschrift zum Abfallgesetz (TA-Abfall) Teil 1: Technische Anleitung zur Lagerung, chemisch-physikalischen, biologischen Behandlung, Verbrennung und Ablagerung von besonders chungs-beden Abfen, Gemeinsames Ministerialblatt (joint ministerial circular) Nr. 8, p. 139 - 214 dated March 12, 1991.

24. Allgemeine Verwaltungsvorschrift indestanforderungen an das Einleiten von Abwasser in Gewer (Eisen- und Stahlerzeugung), GMBl (joint ministerial circular). 1982, p. 297.

Deutsche Forschungsgemeinschaft: Liste maximaler Arbeitsplatzkonzentrationen (MAK-Wert-Liste), 1990, Mitteilung XXVI, Bundesarbeitsblatt 12.1990, p. 35.

DIN 4301 (April 1981): Eisenhchlacke und Metallhchlacke im Bauwesen.

EC Council Directives of 12 May 1986 on the protection of workers from the risks related to exposure to noise at work - 86/188/EEC and of June 14 1989 -89/392/EEC on the approximation of the laws of the Member States relating to machinery.

Environmental Protection Agency (EPA): Effluent Guidelines for Iron and Steel

Manufacturing (CFR 420); Iron and Steel Development Document (Volumens I - VIII); Regulations on Standards of Performance for New Stationary Sources (40 CFR 60).

Hinweise f Einleiten von Abwasser in eine ntliche Klnlage, Arbeitsblatt A115 (January 1983) der Abwassertechnischen Vereinigung e.V., St. Augustin.

Lschutz an Hochofen- und Sinteranlagen, herausgegeben vom Minister feit, Gesundheit und Soziales des Landes Nordrhein-Westfalen, Dorf, 1982.

Lschutz an Elektrostahlwerken, herausgegeben vom Minister feit, Gesundheit und Soziales des Landes Nordrhein-Westfalen, Dorf, 1982.

Technische Anleitung zum Schutz gegen L (TA-L) dated July 16, 1968, zur Allgemeinen Verwaltungsvorschrift enehmigungsbede Anlagen nach § 16 der Gewerbeordnung, leitet nach § 66 des Bundes-Immissionsschutzgesetzes dated 15.03.1974, Beilage BAnz. No. 137.

Unfallverhvorschriften, Hauptverband der gewerblichen Berufsgenossenschaften, Bonn u.a. UVV-L, VBG 121 dated 01.01.1990.

VDI-Richtlinie 2288, Blatt 1: Auswurfbegrenzung, Kupolofen-Betrieb, September 1971.

VDI-Richtlinie 2288, Blatt 2: Anleitung fubauswurfmessungen an Kupol, August 1971.

VDI-Richtlinie 3465: Auswurfbegrenzung, Stahlwerksbetrieb, Elektrolichtbo-gen, January 1978.

VDI-Richtlinie 3887: Emissionsminderung, Giereien, in Vorbereitung.

VDI-Richtlinie 2058, Blatt 1: Beurteilung von Arbeitsl in der Nachbarschaft, September 1985.

VDI-Richtlinie 2561: Die Gesamtemission von Gesenk- und Freiformschmieden und Maahmen zu ihrer Minderung (L), July 1968.

VDI-Richtlinie 2560: Perscher Schallschutz, December 1983.

VDI-Richtlinie 3572, Blatt 2: Emissionskennwerte technischer Schallquellen; Umformmaschinen, Schmiedepressen, October 1986.

VDI-Richtlinie 2262: Staubbekfung am Arbeitsplatz, December 1973.

VDI-Richtlinie 3929: Erfassen luftfremder Stoffe (Entwurf), March 1990.

VDI-Richtlinie 2058, Blatt 3: Beurteilung von L am Arbeitsplatz unter Berhtigung unterschiedlicher Tgkeiten, April 1981.

Verordnung rbeitssten (Arbeitsstenverordnung ArbStV) dated 20.03.75, BGBl I (Federal Law Gazette I), p. 729, 15: Schutz gegen L.

Dreizehnte Verordnung zur Durchf des Bundes-Immissionsschutzgesetzes (Verordnung roeuerungsanlagen - 13. BImSchV) dated 22.06.83, BGBI (Federal Law Gazette), Teil I, p. 719.

Verordnung zur Bestimmung von Abfen nach § 2 Abs. 2 des Abfallgesetzes dated April 3, 1990, BGBl I (Federal Law Gazette I), p. 614.

Verordnung zur Bestimmung von Reststoffen nach § 2 Abs. 3 des Abfallgesetzes dated April 3, 1990, BGBl I (Federal Law Gazette I), p. 631.

Verordnung as Einsammeln und Befrn sowie ie erwachung von Abfen und Reststoffen dated April 3, 1990, BGBl I (Federal Law Gazette I), p. 648.

Verordnung efliche Stoffe (Gefahrstoffverordnung GefStoffV) dated 26. August 1986, BGBl I (Federal Law Gazette I), p. 1470 in the version dated. August 23, 1990, BGBl I, p. 790.

Scientific / technical papers

Abwassertechnische Vereinigung: Lehr- und Handbuch der Abwassertechnik, Band VI, Industrieabwer mit anorganischen Inhaltsstoffen, Verlag fhitektur und technische Wissenschaften, Berlin 1985.

Aichinger, H.M., Borgsschulte, B., Britz, H., Held, B., Meyer, O., Strohschein, H.: Stand des primnergiesparenden Konvertereinsatzes in der Bundesrepublik Deutschland, Stahl u. Eisen 108, 1988, No. 13, p. 645 - 654.

Anonym: Die neue Entstaubungsanlage im Oxygenstahlwerk Beeckerwerth der Thyssen Stahl AG, Stahl u. Eisen 110, 1990, No. 4, p. 137.

Baum, J.P., Gerhardt, J.W.: Abgasreinigungsanlagen in der Eisen- und Stahlindustrie und ihre Kosten. in: Stand und Entwicklung der Anlagentechnik im Eisenhesen, Haus der Technik-Verntlichung No. 369, Essen.

Bogdandy, L., Nieder, W., Schmidt, G., Schroer, U.: Die Schmelzreduktion von Eisenerz nach dem Corex-Verfahren im kraftwirtschaftlichen Verbund, Stahl u. Eisen 109, 1989, No. 9, p. 445 - 452.

Buckel, M., Kersting, K., Kister, H., L H.: Neue Entwicklungen bei der Sinterherstellung, Stahl u. Eisen 110, 1990, No. 2, p. 43 - 51.

Direktreduktion von Eisenerz, Verlag Stahleisen mbH, Dorf, 1976.

Dreyhaupt, F.J.: Handbuch fissionsschutzbeauftragte, Verlag T Rheinland, Cologne, 1981.

Fischer, B., R H., D, W., Nagels, Gl., Knorre, H.: Entgiftung cyanidhaltigen Gichtgaswaschwassers von Hoch, Zeitschrift fser- und Abwasser-Forschung 14, 1981, No. 5/6, p. 210 - 217.

Fleischer, G.: Abfallvermeidung in der Metallindustrie, EF-Verlag frgie- u. Umwelttechnik GmbH, Berlin, 1989.

Geiseler, J., Drissen, P., Treppenschuh, H.: Metallurgische Verwertung von Stauben und Schlen der Stahlindustrie, Stahl u. Eisen 109, 1989, No. 7, p. 359 -365.

Gemeinfaiche Darstellung des Eisenhesens, Verlag Stahleisen mbH, Dorf, 1971.

Grebe, K., Gr, G., Lehmk H.J., Schmauch, H.: Die Metallurgie der Direktreduktion von Heststoffen nach dem Inmetco-Verfahren, Stahl u. Eisen 110, 1990, No. 7, p. 99 - 106.

Grher, K., de Haas, H., Mohnkern, H., Ulrich, K., Kahnwald, H.: Staubunterdr in Hochofengieallen, Stahl u. Eisen 111, 1991, No. 3, p. 51 - 56.

Haering, H.U.; Polthier, K.: Gerchemission und Lminderung von Gesenkschmieden, Stahl u. Eisen 108, 1988, No. 4, p. 179 - 184.

Haering, H.U.; Mrs, K.H.; Neugebauer, G.; Polthier, K.: Lminderung durch Einhausung von Lichtbogen, Stahl u. Eisen 109, 1989, No. 7, p. 343 -349.

Haucke, M., Theobold, W.: Behandlung und Aufbereitung von Sten und Schlen in der Stahlindustrie, Gewerschutz-Wasser-Abwasser, Aachen, Bd. 21, 1976, p. 511 - 54.

Kaas, W.: Handhabung von Walzzunderschlamm, Stahl u. Eisen 101, 1981, p. 963 -965.

Krumm, W., Fett, N., Pen, H,. Strohschein, H.: Optimierung der Energieverteilung im integrierten Herk, Stahl u. Eisen 108, 1988, No. 22, p. 1097 - 1106.

K., Haucke, M.: Erfahrungen bei der Behandlung und Verwertung von Stahlwerkssten and -schlen, Stahl u. Eisen 101, 1981, p. 701 - 705.

Lange, M., Minimierung der Dioxin- und Furanemissionen aus Abfall -verbrennungsanlagen, T32, 1991, No. 3, p. E35 - E40.

Lemission und Lminderung an Elektrolichtbogen, Verbesserung des Gesundheitsschutzes f Belegschaft. Bericht No. 809 des Betriebs -forschungsinstituts Dorf.

Lquellen der Eisen- und Metallindustrie, Ed.: Berufsgenossenschaftliches Institut fmbekfung, Mainz, 1973.

Meinck, F.; Stooff, H.; Kohlsch H.: Industrie-Abwer, Stuttgart, Gustav Fischer Verlag, 1968, 4. Aufl.

Ministerium feit, Gesundheit und Soziales des Landes NW: Luftreinhalteplan Ruhrgebiet West, 1. Fortschreibung, 1984 - 1988, Dorf, 1985.

Philipp, J.A. et al: Umweltschutz in der Stahlindustrie, Entwicklungsstand -Anforderungen - Grenzen, Stahl u. Eisen 107, 1987, No. 11, p. 507 - 514.

Philipp, J.A., Maas, H.: Abfallwirtschaft in einem Herk, Stahl u. Eisen 104, 1984, p. 403 - 407.

Rat von Sachverstigen feltfragen: Umweltgutachten 1987, Verlag W. Kohlhammer GmbH, Stuttgart.

Rat von Sachverstigen feltfragen: Sondergutachten Altlasten 1989, Sondergutachten Abfallwirtschaft 1990, Verlag Metzler-Poeschel, Stuttgart.

Reichelt, W.; Kapellner, W.; Steffen, R.: Endabmessungsnahe Herstellung von Flachprodukten, Stahl u. Eisen 108, 1988, No. 9, p. 409 - 417.

Schallschutz in Giereien, Teil 1: Beschreibung von Giereien und Zusammenstellung von vorhandenen Erkenntnissen as Gerchemissions- und Immissionsverhalten, Studie des T Rheinland im Auftrag des Ministers feit, Gesundheit und Soziales des Landes Nordrhein-Westfalen, Dorf, 1983.

Schmidt, H.: Schalltechnisches Taschenbuch, VDI-Verlag, Dorf, 1984.

Steffen, R., L H.: Stand der Direktreduktion von Eisenerzen zu Eisenschwamm, Stahl u. Eisen 108, 1988. No. 7, p. 339 - 343.

Umweltbundesamt [German Federal Environmental Agency]: Altanlagereport 1986, Umweltbundesamt Berlin, 1986.

Umweltbundesamt [German Federal Environmental Agency]: Jahresbericht 1988, 1989 und 1990, Umweltbundesamt Berlin.

Umweltbundesamt [German Federal Environmental Agency]: Checklisten zur Prder Umwelterheblichkeit raumbedeutsamer Vorhaben "Metallverarbeitende Industrie". UBA-FB 87-039, Werbung und Vertrieb Verlag, Berlin 1988.

VDI-Kommission Reinhaltung der Luft: Schwermetalle in der Umwelt, Dorf, 1984.

Vigder, I.: Wasserkreisle f Stahlindustrie, Stahl u. Eisen 103, 1983, p. 1195 -1197.

Wischmann, G.: Gerchemission von Schmiedepressen und Mchkeiten zur Lminderung, Schriftenreihe der Bundesanstalt feitsschutz [German Federal Institute for Occupational Health and Safety], Dortmund, 1984, Heft Fb 393.

1. Scope

Since the non-ferrous metals sector covers a multitude of individual products, charge materials, fuels and processes, this brief can only deal with a few examples of the principal industrial non-ferrous metals. Environmental impacts and protection measures in the production and processing of aluminium, copper, lead and zinc are dealt with as representative of the large number of other non-ferrous metals as well.

The non-ferrous metals sector comprises the subdivisions:

- smelting of appropriately pretreated primary raw metals to produce metals
- processing recycling material in secondary smelting plants, and
- processing of metals to produce standard commercial billets and blanks.

2. Environmental impacts and protective measures

The following deals primarily with the environmental factors arising in the application of current standard processes. For projects using pyrometallurgical processes these are primarily air protection measures; slags are also produced which, depending on their composition, can be a danger to soil, water and living things. In hydrometallurgical treatment processes, measures to protect water and soil predominate.

Since most processes generate noise, the possibility of noise pollution occurring both in the work-place and in the neighbourhood must be taken into account.

Non-ferrous metal production plants occupy a considerable amount of space to accommodate the works site with adjoining areas and connecting roads.

Different quantities of energy are required depending on the production process. The choice of location partly depends on the availability of sufficient low-cost electricity, e.g. in the case of aluminium production. An encapsulated furnace producing aluminium by igneous electrolysis, with a current load of 200 kA and d.c. voltage of 4.2 V requires approximately 13 kWh/kg aluminium. Zinc production with the stages of roasting, leaching, neutralization, leachate cleaning and electrolysis requires 4 kWh/kg zinc. Values for copper production are somewhat higher. Energy requirements of secondary smelting plants are considerably lower: 20% of the primary smelting energy requirement with 100% scrap copper, around 40% with 100% scrap zinc and 10% with 100% scrap aluminium.

2.1 Aluminium extraction

The Bayer process is used almost exclusively for producing aluminium oxide, the charge material for primary aluminium smelting plants. Bauxite is treated with soda lye under pressure and heat in autoclaves to produce aluminium hydroxide and red mud. The latter is separated, washed and filtered, and may be recyclable or may have to be dumped. After sedimentation and filtration, the aluminium hydroxide is converted to aluminium oxide (alumina) by fluidized bed calcination at around 1100°C.

Large quantities of red mud (1 - 2 t/d Al2O3) are produced. Depending on its composition and the situation in the country in question, it should be used for extracting aluminium oxide and iron, producing flocculation agents for wastewater cleaning or the manufacture of building materials. Red mud which cannot be further processed must be dumped. Where it is stored on a dump, special requirements must be met in respect of sealing and treatment of percolation water. Dumping should be on a single-purpose dump subject to continuous supervision.

A considerable amount of fine dust may be produced upon loading, unloading and transport of fine-grained materials (bauxite, alumina) unless enclosed conveyor systems and suitable storage facilities are provided. Waste gas from the calcination furnaces contains dust with an aluminium oxide content which is deposited in dry filters and recirculated. Dust emissions in cleaned waste gas are under 50 mg/m3.

The process most commonly used for extracting pure aluminium is igneous electrolysis. Aluminium oxide at approximately 950°C is dissolved in a molten mixture of aluminium fluoride and cryolite and separated by direct current into pure aluminium and oxygen. The liquid aluminium is periodically drawn off and cast.

The following emissions and raw materials occur with the extraction of pure aluminium:

- primary alumina dust during storage, transport and charging;
- primary dust during anode production (petroleum coke etc.);
- volatile binding agents, fluorine from anode residues in the waste gas from the anode burning kilns;
- fluorides (dust and gaseous form) in the pot waste gas containing CO/CO2; hydrogen fluoride gas is highly corrosive, harmful to health and the environment (also affects plant growth);
- used cathodes, containing fluoride;
- furnace breakage materials with fluoride components;
- wastewater.

The following individual protection measures are necessary:

Fine dust: Use of enclosed conveying systems (e.g. pneumatic conveyors).

Anode production: Extraction of dust and gaseous emissions, electrostatic waste gas cleaning, wet-chemical fluorine separation. Use of fabric filters permits clean gas dust concentrations of under 20 mg/m3 and fluorine contents of under 1 mg/m3.

Pots: Pot encapsulation with anode gas extraction and waste gas cleaning, wet chemical fluorine recycling or combined dedusting and dry absorption in the Al2O3 fluidized bed with direct recirculation. Wet chemical separation with water recirculation produces a sludge which, after drying, can only be partly returned to the process. Dry absorption and return of the filter dust to the process is preferable as this relieves the burden on the water circuit. Clean gas dust contents of under 30 mg/m3 and fluorine compounds of under 1 mg/m3 are obtained with encased, centrally controlled, large-capacity furnaces with computerised waste gas regulation and dry absorption with fabric filter.

Cell house: Shop air extraction and cleaning is compulsory with non-encased furnaces. Can be retrofitted.

Cathode and furnace Dumping only on specially protected, single-purpose breakage: dumps Cryolite, used as a fluxing agent for the electrolysis, can be obtained by processing (fluorine recycling).

Wastewater: The discharge of wastewater from aluminium oxide production and aluminium smelting must satisfy the requirements laid down under the generally recognised standards regarding chemical oxygen demand for aluminium and fluorides.

With respect to noise, a distinction is made between noise emissions affecting the neighbourhood and those affecting the workplace. Emission from main noise sources can be restricted by encapsulation and by means of silencers on air intakes and outlets. A noise reduction plan should be prepared during the planning phase.

2.2 Heavy metal ore smelting

The composition of the concentrates or raw materials is crucial for the applicable smelting process and thus also for the nature and quantity of the environmental pollutants arising. Sulphidic ore concentrates are thus mostly smelted by pyrometallurgical processes, whilst hydrometallurgical processes are employed for oxidic, sulphidic-oxidic and complex ores.

Combined processes are also used in which, for instance, material roasted by a pyrometallurgical process undergoes further treatment by hydrometallurgy. The charge material is ore enriched by beneficiation.

· Pyrometallurgical process stages

Roasting: Partial or total desulphurization (dead roasting) of the charge material;

Sinter roasting: Roasting of sulphur with admission of air (conversion of sulphides to metal oxides and SO2 gas) with simultaneous agglomeration of the roasted material for use in shaft furnaces;

Rolling: Metal oxide enrichment by controlled volatilization (Zn);

Smelting: Separation of gangue (slags): production of high grade metal sulphides (Cu2S) by partial combustion of the sulphur content and reduction of metal oxides (PbO, ZnO) under coke combustion with air admission;

Fuming: Conversion of metal sulphide to metal in a converter;

Pyrometallurgical Cleaning molten metal of oxygen, sulphur, impurities refining: and tramp metals by intermetallic precipitation, slagging and/or volatilization;

Slag cleaning: Thermal processing of slags to extract metal components.

Numerous emissions and residual materials occur with the above processes:

- Waste gases of various origins
- Primary dust from the charge material,
- Dusts from volatilized metals, including lead, zinc, arsenic, tin, cadmium, mercury, selenium, tellurium and their compounds (condensed after cooling),
- gaseous materials including SO2, HCl, HF, CO, CO2;
- Wastewater from coolant circuits and waste gas scrubbing;
- Final slags with residual metal contents, sulphates, sulphides; possibility of polychlorinated dibenzo-dioxins and -furans with chlorinating methods (e.g. copper roast leaching process);
- Furnace breakage materials, containing arsenic, lead, cadmium, mercury and cyanide.

For protective measures to be effective, it is essential that all emissions, including diffuse emissions of gas and dust, be efficiently intercepted at their points of origin. Diffuse emissions can be intercepted by hoods, covers or encapsulation, also by constructional measures such as encasement of conveyor belts or enclosed bays. Roasting furnaces should not be outdoor installations.

Dust: Waste gases are normally dedusted in dry filter systems (cyclones, electrostatic precipitators, fabric filters). Dedusting efficiency of up to 99.9% is possible, but depends on the permissible solid or pollutant content. Dusts can also be separated with fabric filters in lead smelting plants. Good separation efficiency is particularly important for the environment because waste gas from smelting contains toxic substances such as arsenic, antimony and lead in the form of fine dust. High-performance filtering separators have proved effective for fine dust separation.

Dust recycling for enriching and recovering metals. Separate pyrometallurgical or hydrometallurgical processing of tramp metals, for example As, Cd. Fabric filters are the principal method of dust separation. Clean gas dust contents of 10 mg/m3 can be obtained. Best values are around 1 mg/m3, e.g. in lead smelting plants.

SO2 gas: Removed by waste gas scrubbing followed by neutralization. SO2 concentrations in waste gas of over 3.5% are suitable for sulphuric acid production. In certain circumstances liquid SO2, gypsum or elementary sulphur can be produced as a possible preliminary stage for industrial usage. Wet chemical waste gas cleaning processes are used for lower SO2 concentrations. Only limited SO2 concentrations and overall quantities may be discharged via chimneys.

Oil mists: If oil mists are present in the waste gases from shaft furnaces on account of the charge material, waste gases must undergo thermal afterburning.

Final slags/ Slags and furnace breakage material should be stored furnace breakage: in a specially protected single-purpose dump, since toxic and water-polluting substances such as heavy
metals may be released through leaching and weathering. Depending on residual metal content and
concentrations of other substances such as sulphides, sulphates, dioxins and furans, may possibly be used for road construction or reprocessing, or may have to be discarded.

Wastewater: Wastewater from waste gas scrubbing and slag granulation is polluted with heavy metals. Dissolved and undissolved metallic compounds in communal treatment plants lead to excessive metal concentrations in sewage sludges, restricting or preventing agricultural use.

Measures for reducing pollutant loads include minimizing wastewater volumetric flow by recirculation, recycling of treated wastewater and separating wastewater requiring treatment from that not requiring treatment. Extremely high standards must be applied to the discharge of wastewater with metal compounds toxic to humans and the ecosystem. State-of-the-art wastewater treatment systems include selective ion exchangers, microfiltration systems, reversal osmosis and thermal concentration processes. Production-specific concentrations of cadmium, mercury, lead, zinc, arsenic, copper, nickel and chromium should be limited.

Significant waste gas and emission reductions are achieved by combining several process steps in modern processes such as the flash cyclone reactor and the flash smelting method. Trials in a copper smelting plant and a lead smelting plant yielded reductions of 75%.

· Hydrometallurgical processes

Charge materials are oxidic ores, pretreated sulphidic ore concentrates which can be hydrometallurgically treated, or sulphidic concentrates which undergo oxidizing leaching. Hydrometallurgy processes also include extraction and refinement electrolysis.

Leaching: Treatment and lixiviation of the metals to be recovered, e.g. with dilute sulphuric acid for zinc production. For dump leaching in the case of very low-grade ores (bottom sealing necessary for soil and ground water protection);

Enrichment: Concentration of weak solutions by fluid extraction, using an organic solvent with simultaneous leachate cleaning.

Cleaning: Separation of accompanying substances and impurities by solids-fluid extraction and/or precipitation (hydroxide or sulphide precipitation, cementation);

Extraction: Electrolytic metal deposition with insoluble anodes (e.g. with Zn, Cu);

Refining: Electrolytic metal deposition with soluble anodes (e.g. with Cu, Pb).

The following environmentally relevant emissions and substances may be produced with the above processes:

Wastewater: Greater or lesser quantities of zootoxic and phytotoxic heavy metal components may be present in the wastewater, depending on the charge materials.

Leachate residues: Leachate residues contain metallic compounds harmful to the environment.

Waste gases: Sulphuric acid mists are produced in the extraction electrolysis; metal-containing vapours, e.g. in crude copper anode furnaces; organic solvents, e.g. xerosin, during liquid extraction in the enrichment process.

Anode sludge: This sludge contains metals and metal compounds, e.g. gold, silver, lead, tin, arsenic, antimony.

Spent electrolyte: The electrolyte contains dissolved metallic compounds of iron, nickel, zinc, arsenic and cobalt.

The following individual protection measures are necessary:

Wastewater: The wastewater volume must be reduced by appropriate measures, e.g. recirculation, recycling. Wastewater containing heavy metal pollutants must be treated by state-of-the-art methods. Wastewater contaminated with e.g. cadmium and mercury must be channelled and treated separately.

For wastewater treatment, especially low production-specific concentrations are to be stipulated, with residual concentrations of under 1 mg/l Cd and under 0.1 mg/l Hg to be achieved. Suitable processes include ion exchange, ultrafiltration and electrolysis.

Leachate residues: Residues must be converted by washing and neutralization processes to form compounds suitable for final dumping. Where technically possible, solvent residues are to be eliminated.

Waste gases: Permissible work-place concentrations for sulphuric acid mist can be achieved by appropriate room air ducting and, where necessary, waste air scrubbing.

By equipping a crude copper anode furnace with fabric filters, it was possible to separate gaseous metallic compounds to clean gas concentrations of 0.001 mg cadmium/m3, 0.05 mg lead/m3 and 1.9 mg/arsenic/m3. With liquid extraction using organic solvents, precautions must be taken against combustion and explosion and for fire fighting.

Anode sludge/ Special hydrometallurgical or pyrometallurgical electrolyte: measures are to be employed for the phased recovery of useful materials and the extraction of tramp metals; e.g. electrolytic deposition of arsenic and antimony or precipitation of nickel, iron or cobalt.

The extraction of zinc from zinc blende or galmei inevitably yields 3 to 4 kg cadmium per tonne of zinc as an alloy element in crude zinc or in the form of residues. Cadmium is extracted in primary zinc smelting plants by dry and wet absorption processes. The generally preferred wet processes and electrolytic cadmium extraction result in no direct production of cadmium dusts. The waste gases resulting from the smelting of cadmium to produce commercial formats can be introduced to the air for roasting, in order to achieve total waste gas cleaning.

Due to the toxic effects of cadmium, strict requirements must be imposed on work-place hygiene and waste air and water cleaning. In heavy metal ore smelting operations, main noise sources are wherever possible to be restricted by encapsulation and by means of silencers on air intakes and outlets. A noise reduction plan should be prepared at the project planning stage. In the case of operations generating high levels of noise, one should preferably begin by damping or eliminating occurrences and noise sources which arise only periodically.

To protect work-places from noise, installations should be extensively automated and equipped with appropriate control rooms. Protective equipment includes fireproof clothing, breathing equipment and ear protectors, depending on where they are working; protective helmets and safety footwear must be worn in all areas.

Measures for safety in the work-place and to protect the soil of the works site include all precautions to prevent the discharge of water-polluting substances. Special attention is to be paid to installations for producing, handling and using water-polluting substances. Relevant precautions include storage tanks with leakproof drip trays, overfilling safeguards, sealed and impermeable floor surfaces and leak testing, and these should be set forth in a manual.

2.3 Secondary smelting plants

Secondary smelting plants process mainly recycling material (shredder scrap, cables, batteries etc.), heavily contaminated mixed scrap, production scrap with alloy constituents that are difficult to remove, also slags, dross and other metalliferous residues. Predominantly pyrometallurgical processes are employed for metal recovery.

Environmental burdens stem mainly from impurities and pollutants present in the charge material, e.g. oil, paint, plastics, solvents or salts.

Special characteristics of the emissions and substances and requisite safeguards are as follows:

· Aluminium scrap melting plants

Salt slags: Aluminium scrap is usually melted down in rotary or hearth type furnaces under a layer of liquid salt to prevent ingress of air. The salt absorbs impurities present in the scrap and occurring during the melt-down process and produces salt slag (0.5 t/t Al).

Dumping these salt slags seriously pollutes the dump percolation water, therefore salt slag should be processed and returned to the melting process.

Waste gases: The molten aluminium is refined in converters using chlorine gas. The waste gases contain dusts, gaseous chlorine and fluorine compounds and chlorine gas; they may also contain organic substances which, depending on the operating conditions, may include traces of especially environmentally hazardous materials such as polychlorinated dibenzo-dioxins and -furans. Adequate separation of the dusts and inorganic compounds is achieved by dry absorption and fabric filters. Emissions of organic substances can be minimized by scrap sorting and cleaning or by special thermal afterburning of the waste gases.

· Copper scrap melting plants

Dust: When melting down copper-bearing residues, the interception and dry separation of emissions produced on charging and running-off are particularly important. Where oil mist occurs due to the impurity of the copper scrap, waste gases must undergo thermal afterburning before dust separation. For ecological and economic reasons, melting down should take place in a converter with top lances in a shop with waste air collection and cleaning rather than in shaft furnaces.

· Lead scrap melting plants

Waste gases: When recycling scrap batteries, PVC residues may give rise to gaseous inorganic chlorine compounds which are absorbed in the dust and in the slag.

Depending on the operating conditions, small quantities of polychlorinated dibenzo-dioxins and -furans may be present in the waste gases when recycling scrap cables. Emissions of health-endangering dioxins and furans can be restricted by careful sorting of scrap lead, scrap batteries and cables. Trials are in progress on activated-charcoal-based equipment for separation of these substances. Cleaning of scrap batteries results in varying quantities of battery acid (sulphuric acid) entering the washing water. The washing water is contaminated with lead, antimony, cadmium, arsenic and zinc. Separate interception and treatment is necessary.

2.4 Non-ferrous metal semifinishing works

In semifinishing works, the main problems of maintaining clean air stem from the upstream format foundries. These use large amounts of defined scrap in addition to primary metal which may call for pyrometallurgical smelting refining (e.g. with chlorine gas compounds in the case of Al).

Oily and plastic-coated scrap produces soot, oil mist, chlorine- and fluorine-bearing acid mist and similar substances on being melted down. Formation of polyhalogenated dibenzo-dioxins and -furans cannot be ruled out. For this reason scrap should be precleaned in fuming furnaces with afterburning chambers; depending on the permissible level of purity, waste gases are to be cleaned in electrostatic precipitators and/or gas scrubbers.

Waste gas from melting furnaces can contain metal oxides, volatile metalliferous vapours and halogen compounds which must be separated in dust filters or waste gas scrubbers. Through process automation and the use of additional reactors, even low-capacity secondary smelting plants (2,400 t/a) can achieve low clean gas emission values, e.g. 5 mg/m3 dust, less than 1 mg/m3 fluorine compounds, by chemisorption combined with cyclone and fabric filter. Separation efficiency for chlorine compounds can be as high as 98%.

Cooling bays for gas-emitting dross and slag are also to be connected to centralized waste air extraction systems.

Alkaline or acid solutions should be used for degreasing, cleaning and pickling metal surfaces. Organic solvents containing halogens should be avoided. Flushing water and used pickling and washing liquids are to be treated in neutralization plants.

Sludge residues are either pyrometallurgically processed in a smelting plant or, if they contain no pollutants, dumped. Vapours from heated pickling and rinsing baths must be extracted, precipitated by gas scrubbers and neutralized. Polluted waste must be placed on protected dumps with collection of percolation water.

As non-ferrous metal semifinishing plants are frequently situated close to residential zones, consideration must be given to noise reduction measures and the necessary distance.

3. Notes on the analysis and evaluation of environmental impacts

Non-ferrous metal industrial operations using thermochemical or pyrometallurgical processes produce considerable quantities of waste gases laden with environmentally harmful substances. Air protection measures must therefore be a priority.

The following examples illustrate the possible pollutant content of the waste gases:

- aluminium smelting plant, toxic fluorine components in the anode gas raw gas approx. 10 kg F/t Al
- copper smelting plant, sulphur dioxide in the waste gas raw gas approx. 2.6 t SO2/t Cu

The values indicate that even in regions with low levels of existing pollution, waste gases from metal smelting plants must on no account be discharged uncleaned. Wet and dry processes are available for cleaning, dry processes being preferred for ecological and economic reasons.

Continuous monitoring involving measurements to verify the effectiveness of the separation systems is necessary both after erection of the plant and during its operation. Detailed descriptions for carrying out emission and immission measurements are contained in the guidelines of the German Association of Engineers VDI. In Germany the obligatory emission and immission values are detailed in TA-Luft (Technical Instructions on Air Quality Control).

In plants using hydrometallurgical processes, to reduce environmentally harmful substances to a minimum, intermediate products and residues must undergo repeated chemical treatment, filtration, electrolytic precipitation or scrubbing with subsequent neutralization. Wastewater from gas scrubbing or pickling plants may only be returned to receiving bodies of water once it has been chemically neutralized and freed of solids. Guideline values for permitted pollutant concentrations must be established for discharging wastewater in accordance with the state of art. Reference values may be obtained from the regulations in force in Germany. In every case care must be taken to ensure that drinking water and other water resources are not impaired. Analytical processes have been defined under German DIN standards to determine pollutant concentrations in wastewater; in Germany these are detailed in Allgemeine Verwaltungsvorschriften [General Administrative Regulations]. Routine measurements are also to be carried out to monitor the efficiency of water treatment and clarification plants. The scope of measurements and the inspection and maintenance intervals of wastewater - and waste gas - cleaning systems must be defined in an operating manual.

Contaminated material is to be stored in such a way as to prevent soil and groundwater contamination. Where possible, single-purpose dumps should be established, with sealing and percolation water collection and treatment systems which satisfy stringent requirements.

As in Germany, works environmental protection officers should be deployed in non-ferrous metal works who are totally independent of the production side. They are obliged to monitor adherence to the regulations.

In addition to monitoring external pollutant discharge, internal work-places must also be inspected for pollutant concentrations, noise and safety. Suitably qualified safety officers and a works doctor should be appointed for these purposes.

4. Interaction with other sectors

Normal annual production capacities of newer non-ferrous metal smelting plants are between 50,000 and 100,000 t. Allowance must be made for future capacity expansions. Due to the quantity of land occupied and the environmental pollution involved, projects cannot be considered in isolation. As early as the initial location selection phase, existing prior pollution of air, water and soil must be taken into account, making adequate allowance for the additional burdens imposed by such an industrial complex. As early as the planning phase, and when defining permissible immissions, effects on the environment must be considered from the point of view of community development. Adequate distancing from the nearest residential zones is to be guaranteed. Further details are contained in the environmental brief Planning of Locations for Trade and Industry.

Raw materials for smelting plants have to be extracted in large quantities from underground or surface mines. The environmental briefs on mining provide information on the environmental impacts. Efficient transport routes are necessary for transporting charge materials and products. Details are contained in the briefs Road Traffic, Railways and Railway Operation and Shipping.

A special secondary effect of the use of electrolytic processes is that their profitability, and particularly that of an aluminium smelting plant depends on the availability of cheap electricity. Additional pollution results from the erection or extension of power stations and the associated construction, particularly of hydraulic engineering works (see environmental briefs Thermal Power Stations and Power Transmission and Distribution).

A single-purpose dump must be established for non-recyclable products and waste, including slag and furnace breakage material (see environmental brief on Disposal of Hazardous Waste and Volume III, Compendium of Environmental Standards).

5. Summary assessment of environmental relevance

Processes and raw materials utilized in non-ferrous metal smelting plants for extracting aluminium, copper, lead and zinc, and also refining and smelting plants for further processing, produce emissions and raw materials which can pollute the environment. Of special significance are heavy metals which endanger health and in some cases are carcinogenic. In many countries this concerns especially the poorer sections of the population who are particularly at risk due to malnutrition and illness. The same of course applies to metal smelting plants other than those mentioned here.

Environmental damage can be reduced by selecting locations with relatively insensitive landscapes where there is unlikely to be any great effect on the regional productiveness of the natural environment. It is also necessary to exclude regions that are already heavily burdened with high existing or background levels of fluorine compounds and heavy metals. In this regard it should be noted that anthropogenic heavy metals are often more readily plant-available than lithogenic or pedogenic heavy metals.

Pyrometallurgical processes cause mainly air pollution in the form of gases, mists and dusts which must be minimized in gas scrubbers or returned for further processing. Apart from the ecological benefit, this form of emission reduction has the economic benefit of recovering valuable metals or producing sulphuric acids. Similar conditions exist for secondary smelting plants but with the additional problem of polluted charge materials. Depending on the operating conditions, halogen-bearing pollutants combined with organic materials are a particular potential source of polyhalogenated dioxin and furan emissions (waste gas emission concentrations of the order of nanograms).

Emissions and residues from hydrometallurgical processes on the other hand can pollute wastewater and dumps. Recycling of water in the circulation system is very important. Though it is state-of-the-art practice to recirculate liquid process materials such as acids, alkalies or solvents by regeneration, thereby reducing residues, these must be subsequently processed and the waste products neutralized in more or less costly stages to recover valuable metals and/or extract pollutants. Checks must be made in every case to determine whether pollution of groundwater or surface water is possible due to the storage or emission of primary, intermediate or end products. Pollutant yield and hence the necessary outlay for pollutant reduction is significantly lower in the case of semifinishing works.

A survey should be conducted in every case to determine whether agricultural use of the land in the vicinity of the works will be impaired by large-area pollution with phytotoxic and zootoxic heavy metals, especially zinc, copper, chromium, nickel and lead, taking into account long-term deposition, accumulation and reactivity in the soil. The environmental risk resulting from heavy metals in the soil must be distinguished according to the form of bonding of their elements which in turn depends on their origin.

Heavy metals, especially cadmium, can be injurious to human health through accumulation in the soil and in plants, with increased absorption through the food chain, leading in particular to kidney damage. Preliminary calculations of the expected additional environmental burdens are necessary for assessing these indirect effects via the air - soil - food chain. As a precaution, it is advisable to restrict agriculture in the immediate vicinity. Conflicts can be avoided or diminished by consulting the affected population groups at an early stage, possibly developing and planning new sources of employment. The question as to whether the increased environmental pollution poses additional health risks and hazards, e.g. for women and children (during pregnancy etc.) should be investigated, and adequate medical care provided. In addition to the pollution burdens, attention must also be paid to the noise emitted by the plant machinery. Depending on the plant design, noise levels as high as 125 dB(A) may be emitted. Noise levels can be minimized by noise reduction measures which are to be specified in a noise reduction plan. The wearing of personal ear protection must be obligatory in workplaces with noise levels in excess of 85 dB(A) and must be monitored.

For environmental protection measures to be effective, it is vital that personnel should be made sensitive to the issues and receive appropriate training. Although the smelting industry already has a range of proven methods and processes at its disposal for effective pollution control, their application can be excessively cost-intensive where pollutant emissions are too low for improvements to be economic but too high to be ecologically harmless. In these cases, bearing in mind the long-term effects of heavy metal pollution, one must give considerable weight to the needs of environmental protection, even putting this before the profitability of the individual plant.

The emphasis of current development work is towards totally enclosed circuits in the production system. The aim is to enclose the circuit to prevent harmful effects on the biosphere through ever better utilization of charge material, production of pure intermediate and end products without recourse to dumping, with improved emission protection and recycling of separated dusts and solids.

6. References

Statutory provisions, regulations

Abwassertechnische Vereinigung (ATV): Arbeitsblatt R 115, Hinweise f Einleiten von Abwasser in eine ntliche Abwasseranlage, January 1983.

Allgemeine Verwaltungsvorschrift zur derung der allgemeinen Rahmenverwaltungsvorschrift indestanforderungen an das Einleiten von Abwasser in Gewer. GMBl (joint ministerial circular). No. 37, 1989, p. 798.

Erste Allgemeine Verwaltungsvorschrift zum Bundes-Immissionsschutzgesetz (Technische Anleitung zur Reinhaltung der Luft - TA-Luft) dated 27.02.1986, GMBl (joint ministerial circular). 1986, Ausgabe A, p. 95.

Zweite Allgemeine Verwaltungsvorschrift zum Abfallgesetz (TA-Abfall) Teil 1: Technische Anleitung zur Lagerung, chemisch-physikalischen, biologischen Behandlung, Verbrennung und Ablagerung von besonders chungsbeden Abfen, vom M 1991, GMBl (joint ministerial circular). No. 8, p. 139.

39. Allgemeine Verwaltungsvorschrift indestanforderungen an das Einleiten von Abwer in Gewer (Nichteisenmetallherstellung). GMBl (joint ministerial circular). No. 22, 1984, p. 350 - 351.

Deutsche Forschungsgemeinschaft: Liste maximaler Arbeitsplatzkonzentrationen (MAK-Wert-Liste), 1990, Mitteilung XXVI, Bundesarbeitsblatt 12, 1990, p. 35.

Environmental Protection Agency (EPA): Effluent Guidelines and Standards for Non-Ferrous-Metals, 40 CfR 421.

GVBl. des Landes Hessen, Teil 1, 31.03.1982.

Ministerium feit, Gesundheit und Soziales des Landes Nordrhein-Westfalen: Umweltprobleme durch Schwermetalle im Raum Stollberg, 1975, Dorf.

5. Novelle zum Wasserhaushaltsgesetz: Mindestanforderungen nach § 7a, BGBl. I (Federal Law Gazette I), p. 1529.

Technische Anleitung zum Schutz gegen L (TA-L) vom 16.07.1968, Beilage BAnz. (Supplement to the Federal Law Gazette) No. 137.

Unfallverhvorschriften: Hauptverband der gewerblichen Berufsgenossen-schaften, Bonn u.a. UVV-L, VBG 121 of 01.01.1990.

VDI-Richtlinie 2262: Staubbekfung am Arbeitsplatz, December 1973.

VDI-Richtlinie 2285: Auswurfbegrenzung, Bleih December 1975.

VDI-Richtlinie 2058, Blatt 3: Beurteilung von L am Arbeitsplatz unter Berhtigung unterschiedlicher Tgkeiten, April 1981.

VDI-Richtlinie 2560: Perscher Schallschutz, December 1983.

VDI-Richtlinie 2058, Blatt 1: Beurteilung von Arbeitsl in der Nachbarschaft, September 1985.

VDI-Richtlinie 2102: Emissionsminderung, Kupferschrotthund Kupferraffinierien, Entwurf February 1985.

VDI-Richtlinie 2286: Emissionsminderung, Aluminiumschmelzflulektrolyse, Entwurf January 1987.

VDI-Richtlinie 3929: Erfassen luftfremder Stoffe, Entwurf March 1990.

VDI-Richtlinie 2310: Bler 30 und 31: Maximale Immissionswerte fi (Blatt 30) und Zink (Blatt 31) zum Schutze der landwirtschaftlichen Nutztiere, July 1991.

VDI-Richtlinie 3792, Blatt 3: Messen der Immissions-Wirkdosis von Blei in Pflanzen, April 1991.

Verordnung rbeitssten (Arbeitsstenverordnung - ArbStV) of 20.03.75, BGBl. I (Federal Law Gazette I), p. 729, 15 Schutz gegen L.

Verordnung efliche Stoffe, Gefahrstoffverordnung (GefStoffV) of 26. August 1986, BGBl. I (Federal Law Gazette I), p. 1470, in the version dated 23. August 1990, BGBl. I, p. 790.

Verordnung zur Bestimmung von Abfen nach § 2 Abs. 2 des Abfallgesetzes of April 3 1990, BGBl. I (Federal Law Gazette I), p. 614.

Verordnung zur Bestimmung von Reststoffen nach § 2 Abs. 3 des Abfallgesetzes of April 3, 1990, BGBl. I (Federal Law Gazette I), p. 631.

Verordnung as Einsammeln und Befrn sowie ie erwachung von Abfen und Reststoffen of April 3, 1990, BGBl. I (Federal Law Gazette I), p. 648.

Verordnung nlagen zum Lagern, Abfund Umschlagen wassergefdender Stoffe und die Zulassung von Fachbetrieben.

Scientific/technical papers

Bureau of Mines, Washington 1973, Control of Sulfur Oxide Emissions in Copper, Lead and Zinc Smelting.

Buann, H.: Stand und Entwicklung des Kupferrecyclings in: Fleischer, G., Abfallvermeidung in der Metallindustrie, p. 159 - 166, Ef Verlag frgie und Umwelttechnik, Berlin 1989.

Corwin, T.K. et al: International Technology for the Nonferrous Smelting Industry, Noyes Data Corporation, Park Ridge NJ, 1982.

Dengler, H.: Behandlung schwermetallhaltiger Abwer in: UTZ Materialien, 1989; Zentrum felttechnik beim Battelle-Institut Frankfurt am Main.

Deutsche Gesellschaft fhnische Zusammenarbeit (GTZ), Dornier-Studie: Erstellung eines Kataloges von Emissions- und Immissionsstandards, October 1984.

Gesellschaft Deutscher Metallh und Bergleute, Hauptversammlungsvortr, Stuttgart 1972, Umweltschutz in der Metallhndustrie.

Gr, Machelet, B., Podlesak, W.: Kontrolle der Schwermetallbelastung landwirtschaftlich genutzer B in der DDR.

Hartinger, L.: Taschenbuch der Abwasserbehandlung f metallverarbeitende Industrie, Carl Hauser Verlag, Munich 1976.

Kirchner, G.: Die Bedeutung von Sekundluminium f Aluminium-Versorgung in: Fleischer, G., Abfallvermeidung in der Metallindustrie, p. 173-179, Ef Verlag frgie und Umwelttechnik, Berlin 1989.

Kloke, A.: Orientierungsdaten ferierbare Gesamtgehalte einiger Elemente in Kulturb, Mitt. VDULFA 1980, p. 1 - 3 and 9 - 11.

Koch, C.T., Seeberger, J.: ologische Mwertung, Verlag C.F. M Karlsruhe, 1984.

Landtag Nordrhein-Westfalen: Plenarprotokoll 11/28 of 03.05.1991.

Lquellen der Eisen- und Metallindustrie: Berufsgenossenschaftliches Institut fmbekfung, Mainz 1973.

Merz, E.: Minimierung der Belastung durch Metalle und Metalloide, Vortrag im VDI-Kolloquium "Krebserzeugende Stoffe in der Umwelt", 23.04.1991. Mannheim, VDI-Bericht in Vorbereitung.

Miehlich, G., Lux, W.: Eintrag und Verfeit luftbr Schwermetalle und Metalloide in B, VDI-Berichte No. 837, 1990, p. 27 - 51.

Persche Mitteilungen: Wirtschaftsvereinigung Metall e.V., Dorf, 1991.

Rademacher, K.D., Ko K.D.: Wassergefdende Stoffe, Springer Verlag, Berlin 1986.

Riss, A. et. al: Schwermetalle in B and Graufwuchs in der Umgebung einer Kupferhn Brixlegg/Tirol, VDI-Berichte 837, 1990, p. 209-223.

Rack, von A.: Integrierter Umweltschutz - die Aufgabe der Zukunft, Erzmetall, 44 (1991), No. 2, p. 67 - 74.

Spona, K., Radtke, U.: Blei-, Cadmium- und Zinkbelastung von B im Emissionsgebiet einer Zinkhn Duisburg, VDI-Berichte 837, 1990, p. 165 - 183.

Ullmanns Enzyklope der technischen Chemie, 4. Auflage, Band 6 (Umweltschutz), Band 7 (Aluminium), Band 8 (Blei), Band 15 (Kupfer), Band 24 (Zink) - 1974/1983.

Umweltbundesamt [German Federal Environmental Agency] Berlin, April 1978: Stand der Technik bei PrimAluminiumh

Umweltbundesamt [German Federal Environmental Agency] Berlin, March 1980: Richtlinien fssionsminderung in NE-Metallindustrien, incl. ausfhe Bibliographie.

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Miller Freeman Publ., San Francisco, 1975.

1. Scope

The different branches of mechanical engineering are concerned with the machining and processing of ferrous and non-ferrous metals. This covers the whole range of production processes, which can be subdivided as follows:

A:	Metal cutting
	* drilling	* milling	* turning
	* planing	* broaching	* sawing
	* filing	* honing	* grinding
	* lapping	* sandblasting	* chiselling
B:	Non-cutting processes
	Thermal bonding
	* oxy-acetylene welding	* electric welding
	* inert-gas-shielded welding	* submerged arc welding
	* build-up welding
	Thermal cutting
	* oxy-acetylene cutting	* plasma cutting
	Forming
	* forging	* deep drawing	* bending
	Dividing
	* punching	* cutting	* shearing
	* nibbling
	Jointing
	* riveting	* adhesive bonding	* soldering
	Surface treatment
	* surface cleaning	* degreasing	* pickling
	* surface coating	* phosphating	* chromatizing
	* electroplating	* enamelling	*hot-dip galvanizing
	* anodizing	* painting, lacquering	* surface annealing

The raw materials used in these processes may have high environmental pollution potential (e.g. heavy metals), and hazardous production materials may be used (e.g. cleaning agents containing chlorinated hydrocarbons). At the same time, vapours, heat and noise are generated, together with various waste products and wastewater, leading to adverse effects on the environment and on man, especially in enclosed areas.

In shipyards, the main process is welding. This is made additionally hazardous by the fact that welders working on bulkheads often have to work in enclosed areas, which further aggravates the health risks discussed below.

2. Environmental impacts and protective measures

A product undergoes numerous production stages in the course of the metalworking process. The environmental impacts of these stages affect the workplace and hence the people working there. They also affect the air, water and soil.

Due to their proximity to the point of origin, it is the workforce who are most seriously exposed to the production hazards. In highly industrialised countries this is the subject of comprehensive worker protection rules. The workplace hazards are listed below, taking as examples the most important and environmentally relevant machining processes. This is followed by a description of the wider environmental effects including the problems of waste disposal.

2.1 Potential hazards of selected operations

2.1.1 Metal cutting

Machining processes such as drilling, milling, turning, cutting, honing, grinding etc. make use of oils and oil preparations for lubricating and cooling tools and workpieces, to prevent overheating and possible melting of the workpiece and tool. Oils are dosed by spraying or pouring systems at rates of up to 100 litre/min. in order to dissipate heat. The spraying of moving and sometimes very hot tools and workpieces produces vapours containing droplets known as aerosols.

Metalworking techniques require appropriate coolants which must combine several different properties (non-foaming, corrosion-inhibiting, non-decomposing etc.).

Such a wide range of properties can only be achieved through the addition of varying quantities of chemical additives. These are added to the coolants in the form of non-water- miscible cutting oils or water-miscible concentrates.

More than 300 individual substances are used as coolant components. The following table divides these into substance groups by areas of application.

Substance group	Reason for use	Examples
Mineral oil	Lubrication effect	Hydrocarbons with different boiling ranges; fatty oil; esters
Polar additives	Enhanced lubrication properties	Natural fats and oils of synthetic esters
EP additives	To prevent micro-welds between metal surfaces at high pressures and temperatures	Sulphurized fats and oils, compounds containing phosphorous, compounds containing chlorine
Anti-corrosion additives	To prevent rusting of metal surfaces	Alkano-amines, sulphonates, organic boron compounds, sodium nitrite
Anti-misting additives	To prevent breakdown of the oil and thus generate less mist	High molecular substances
Anti-ageing additives	To prevent reactions within the coolant	Organic sulphides, zinc dithiophosphates, aromatic amines
Solid lubricants	To improve lubrication	Graphites, molybdenum sulphides, ammonium molybdenum
Emulsifiers	To combine oils with water	Surfactants, petroleum sulphonates, alkali soaps, amine soaps
Foam-inhibitors	To prevent foaming	Silicon polymers, tributyl phosphate
Biocides	To prevent formation of bacteria/fungus	Formaldehyde, phenol, formaldehyde derivatives, cathon MW

A significant increase in certain occupational diseases has occurred parallel with the introduction of the coolants which are now commonplace. According to scientific findings, diseases of the skin and respiratory tracts and cancer may occur.

Where coolant use is unavoidable, mist extraction as close as possible to the point of origin or encapsulation is necessary. Consistent use must be made of personal protection measures such as the wearing of protective clothing and the use of special skin protection substances. Factories should produce skin protection plans.

Bacteria which can have severe effects on health can occur due to the organic nature of coolants. Bacteria formation is promoted by warm/hot ambient temperatures. Anti-bacterial additives are introduced to counter this. Timely replacement of coolants avoids the need for high doses of anti-bacterial additives, which also represent a health hazard. However, this increases the total quantity of waste to be disposed of. Proper storage of "spent" coolants and subsequent separation of emulsified oils and greases, and also of metal compounds and other components, is imperative.

Safety data sheets informing of the danger of coolants and instructions for use should be displayed in the national language(s). It is important that staff are aware of the long-term dangers of coolants; a particular difficulty here being the often creamy, pleasant smelling and seemingly harmless nature of coolants.

No generally applicable limit values exist for coolants in the breathing air. The only guide is the relevant MAK values9) for the individual substances. The management should find out which are the most environment-friendly coolants and ensure that these are procured.

9) The term MAK (maximum allowable concentration) in Germany refers to the maximum possible concentration of a substance in the air of the workplace, in the form of gas, vapour or suspended matter.

2.1.2 Cleaning and degreasing of workpieces

For subsequent surface treatment, adhesive or thermal bonding etc., workpieces have to be freed of substances such as oils, fats, resin, wax, cellulose, rubber or plastics. Solvents are widely used for this purpose. Workpieces can be degreased and cleaned by various methods, for instance by cold, hot and/or vapour degreasing or combined processes.

Cold cleaning frequently involves the use at room temperature in open baths of solvent mixtures whose precise composition is not known to the user. Mixed with air, the vapours of these solvents or solvent mixtures can be explosive. Most solvents represent a health hazard for man.

Solvents are classified as organic compounds such as hydrocarbons, halogenated hydrocarbons, ethers (diethyl-ether, tetrohydrofuran, dioxan), ketones (acetones, methylethylketone) and organic alkalis (sodium hydroxide solution, ammonia) and acids (hydrochloric acid, nitric acid, sulphuric acid).

The most important halogenated hydrocarbons are chlorinated hydrocarbons (CHCs), such as tri-, tetra-, perchloroethylene, dichloromethane, tetrachloroethane etc.10) On account of their grease-dissolving properties and high volatility, CHCs are used in almost every branch of metal working as cleaning agents in cold cleaners and in hot degreasing. The high volatility ensures quick drying after cleaning, but also means it is necessary to monitor solvent concentrations in the workplace. Through skin contact and inhalation, CHCs can damage mucous membranes, central nervous system, liver, kidneys and lungs.

10) The best known are CFCs (chlorofluorocarbons) used in other application e.g. as refrigerants. CFCs are partially responsible for the destruction of the vital ozone layer in the atmosphere. CFCs and carbon tetrachlorides and certain other chlorinated hydrocarbons are banned in Germany under the CFC halogen prohibition directive of 6 May 1991 and the chloro-aliphatic compounds directive.

In addition, most solvents are inflammable and represent a particular pollution hazard for water.

Alternative processes use alkaline aqueous solutions (with surfactants and other washing components in varying concentrations) or water (high-pressure cleaning).

Apart from the need for worker protection, it should be remembered that practically all solvents seriously pollute the environment. Particular problems in this regard include damage due to solvent evaporation, soil and groundwater pollution and the difficulties of disposing of used solvents and solvent sludges.

Foremost among modern methods of alleviating the problems of disposal are primary measures to prevent wastewater occurring in the first place, rather than subsequently treating highly contaminated bath and flushing water before it enters the drainage system. Membrane filtration and ion exchange processes can be used to regenerate process baths and extend their useful life. Similarly, flushing water can be used several times over with continuous dirt and oil separation (recycling via ion exchangers, emulsion cracking and cascade flushing techniques). Resulting wastewater quantities and pollutant loads are reduced. One might also attempt to process and reuse solvents in a closed solvent circuit. This technique is rarely successful in the case of reprocessing surfactants, so the improvement of their biodegradability is an important factor. Management should optimize selection of solvents based on technical and environmental factors11).

11) Only wastewater experts can definitively optimise the choice of solvents. Information is available in: Dagmar Minkwitz, "Ersatzstoffe fogenkohlenwasserstoffe bei der Entfettung und Reinigung in industriellen Prozessen" (serial publication of the Bundesanstalt feitsschutz (German Federal Institute for Occupational Safety and Health) GA 38) Dortmund, Bremerhaven 1991 (Wirtschaftsverlag NW) ISBN-3-89429-086-2. See also "Zeitschrift Oberflentechnik, Bezugsquellennachweis f Oberflentechnik mit Trendchten und Tabellen, Munich, 4th edition 1991) (Seibt Verlag), ISBN 3-922948-70-7.

The following precautions should be taken where degreasing is carried out with organic solvents:

- do not use substances which are unknown;
- use enclosed equipment where possible;
- ensure effective ventilation and aeration of work rooms;
- ensure good extraction at the workplace;
- avoid skin contact;
- use protective equipment;
- as solvents are heavier than air, they force the breathing air out of trenches, cellars, containers and depressions in the ground; suffocation can be avoided by means of floor openings and ventilation;
- use only non-combustible washing vessels with self-closing covers for cleaning small parts with inflammable solvents;
- keep only quantities of flammable solvents at the workplace as are required for the work and store in suitable containers with effectively sealed covers;
- avoid electrostatic charges;
- in operating manuals indicate the solvents used, limitations on use and safety precautions, instruct personnel;
- secure and lock installations when not in use;
- avoid hand-spraying of degreasing agents with spray guns;
- avoid blow-drying with compressed air of surfaces which have been treated with chlorinated solvents;
- with open degreasing equipment, note the quantities of solvent displaced on immersion of the workpiece and dimension the system accordingly;
- workpieces should leave the system free of solvents.

2.1.3 Painting

Most spray paints and brush paints contain considerable quantities of hydrocarbon and chlorinated hydrocarbon solvents (spray paints as much as 90%, normally 50 - 70%) which evaporate on spraying and drying. Paints also contain finely dispersed pigments. Some of these are highly toxic. Depending on the application, paints may have to satisfy a wide range of quality requirements. Available paint systems are accordingly diverse.

There are three possible ways of avoiding solvent emissions from painting installations; these can be used separately or in combination:

- use of low-solvent paints

"High solids" paints, water soluble paints and dispersion paints have been developed for this purpose. A further alternative is solvent-free powder paint, for which new applications are constantly being found.

- use of high-performance application methods

Solvent emissions depend not only on the paint formulation but also on the application method. An important evaluation criterion is the application efficiency factor, which is defined as the ratio of paint remaining on the product to the total quantity of paint used. Lower efficiency means higher paint consumption and thus higher solvent emission. Application efficiency is primarily determined by the process and by the form of the parts to be painted.

The following application efficiency values can be taken as guidelines for the painting of large surface areas by various methods:

- compressed air spraying 65%
- "airless" spraying 80%
- powder painting 98% (with recycling of spraying loss)
- electrostatic spraying 95%
- dipping, flooding 90%
- rolling, pouring approx. 100%
- brush, roller application 98%

The choice of application method depends on certain quality requirements, e.g. coating thickness, surface roughness etc. and is hence closely related to the purpose of the painted object.

The various levels of waste gas resulting from the different methods can be greatly reduced by enclosing the application zone and additionally by air circulation. This will reduce the outlay on waste gas cleaning.

- collection and cleaning of waste gas (with solvent recycling).

2.1.4 Electroplating

To obtain different surface properties (surface refining), workpieces are electroplated with chromium, zinc, tin, copper, cadmium, lead or brass. For this the selected metallic coating is deposited from an electrolyte solution in an electro-chemical process. To enable the metal coatings to be applied, workpieces must be cleaned and degreased.

Where cold cleaning and degreasing are carried out, the hazards from cold cleaners must be taken into account (see 2.1.2). The boil-off technique is also used for rough cleaning. Strong alkalines such as sodium or potassium hydroxide solutions are used for this purpose. These alkalines can damage eyes, skin and respiratory tracts if splashed or given off as mist or dust. An electrolytic process is often used for subsequent fine cleaning. Electrolytes are often alkaline solutions (5% sodium hydroxide solution) or cyanidic salts. Apart from the dangers posed by the boil-off technique, extraction ventilation is necessary in view of the large quantities of hydrogen produced, so as to avoid reaching the explosibility limit of the air-hydrogen mixture. Safety in the workplace is increased by installing gas warning devices.

Pickling degreasers and pickles are used to remove oxidation layers and casting or rolling scale from metal surfaces. These are acids (sodium hydroxide solution for aluminium) such as sulphuric, hydrochloric, phosphoric, hydrofluoric or nitric acid which attack and dissolve the workpiece surface. The main health hazards are skin diseases; dangerous vapours and gases can be inhaled in the case of inadequate extraction. Especially dangerous are nitrous gases which can occur when using nitric acids, also fluorine compounds from hydrofluoric acid and hydrogen chloride from hydrochloric acid.

Cyanides are used for cleaning in salt baths (fluorides), pickling (removal of thin surface films), with chemical and electrolytic polishing or burnishing, and also with surface coating and thermo-chemical hardening processes. These can cause hydrocyanic poisoning as well as skin diseases when solutions containing cyanide come into contact with acids. Therefore baths containing acids and cyanide must be covered and separated by partitions. Containers and equipment are to be clearly marked to prevent carry-over of substances which can mutually react. In all cases one should check to determine whether cyanide can be replaced by substances less hazardous to health.

The actual electroplating of the workpiece can be done in countless different process variants and stages. Materials posing just about every conceivable danger can be used in electroplating. The dangerous properties result both from the main components of the bath fluid and from different additives such as emulsifiers, foam inhibitors and wetting agents.

Strong aerosols can occur during bath filling and further preparation. Dangerous substances may enter the breathing air due to the production of gas (hydrogen) during the electrolytic process.

The main hazards with coatings are skin complaints and in particular allergies due to nickel and chromates. If consumed, both nickel and chromates can be carcinogenic. Nickel in fluid particle form is subject to a TRK value12) 4 of 0.05 mg/m³ breathing air.

12) TRK value: German technical directive on concentration of carcinogenic substances

2.1.5 Welding

Welding is the joining of materials using heat and/or force, with or without the use of welding fillers (anti-oxidation substances).

The individual processes most commonly used are gas welding, arc welding and inert gas shielded welding.

Polluting factors in welding workshops are:

- chemicals in the generated gases, vapours and dusts
- high temperatures (approx. 3,200°C - 10,000°C)
- radiation (ultraviolet radiation): eye damage, severe inflammation of unprotected skin;

infrared radiation: can penetrate the vitreous body of the eye, reaching the retina and causing cataracts)

- noise (up to 110 dB(A))

Diverse hazards occur depending on the fuels, inert gases, filler materials, workpiece coatings etc. in use. The following table summarizes the pollutants occurring with the different welding methods. The carcinogenic and mutagenic elements chrome and nickel are especially relevant. Certain hazardous elements are detectable in welding fumes in concentrations of over 1% and can lead to health damage. Clinical and epidemiological investigations indicate a frequent occurrence amongst welders of chronic bronchitis and increased impairment of the respiratory tracts.

Pollutants occurring in various welding processes include:

Pollutant			Causes	Welding process	MAK * mg/m3
Lead	PbO	Welding of lead or lead-coated workpieces		all	0.1
Chromium	Cr2/ 3	Welding with alloyed electrodes, Cr Ni steel		all
Cadmium	CdO	Cadmium-coated workpieces		all	0.05
Carbon monoxide	CO	Welding with basic coated electrodes, gas flame		all	30
Carbon dioxide	CO2	Gas welding with coated electrodes, inert gas		all	5000
Copper	CuO	Welding of copper, copper-coated workpieces		all	0.1
Manganese	Mn O	Welding of workpieces containing Mn, all electrodes		all	5
Nickel	NiO	Welding of Cr Ni steel, alloyed electrodes		all
Nitrogen	NO2	Welding in confined spaces, trenches, tanks		all	9
Zinc	ZnO	Welding of zinc, galvanized workpieces, zinc paint		all	5
Aluminium	Al2O3	Welding of aluminium, almost all types of electrodes		Arc welding	-
Iron	Fe2O3	Welding of steels, all electrodes		Plasma arc welding	8
Fluorides	F	Welding with basic and alloyed electrodes		Arc welding	2.5
Calcium	CaO	Welding with coated electrodes		Arc welding	5
Sodium	Na2 OH	Welding with coated electrodes		Arc welding	2
Oxygen (ozone)	O3	Strong UV radiation		Plasma arc welding	0.2
Titanium	TiO2	Welding with coated electrodes		Arc welding	8
Vanadium	V2O3	Welding workpieces containing vanadium		Arc welding	0.5

* MAK: maximum allowable concentration

The welding of metals with anti-corrosion coatings may also have adverse toxicological consequences. Pollutants may be released depending on the type of coating.

Alkyl resins: acrolein, butyric acid
Phenolic resins: phenols, formaldehyde
Polyurethane: isocyanates, hydrogen cyanide
Epoxy resins: phenols, formaldehyde, hydrogen cyanide.

Although the inert gases carbon dioxide, argon and helium are not toxic, in poorly ventilated rooms they can displace the breathing air and under extreme conditions cause suffocation. Ozone may be produced during arc welding. Even low concentrations (0.1 parts per million (ppm)) of ozone can cause irritation to the eyes and upper respiratory tracts and in the event of exposure to 5-10 ppm over several minutes, pulmonary oedema.

At high temperatures nitrogen oxides are formed and emitted from the nitrogen and oxygen in the air on the periphery of the welding flame. Nitrogen oxides are highly toxic and, after a relatively long asymptomatic period, can lead to radical lung changes, pulmonary oedema and death. If the workpiece has been degreased with solvents containing chlorine and not properly dried, phosgene may be produced during welding. Phosgene is highly toxic and can also cause pulmonary oedema after a long asymptomatic period.

Since the welding of plastics is not yet widespread in many countries, it is not dealt with here. It must be pointed out however that the hazards for man and the environment are also considerable with the welding of plastics. Protective measures and special disposal procedures are necessary to guard against the release of solvents and other waste gases containing pollutants.

2.1.6 Soldering

Soldering is the thermal joining of two materials using a material (solder) whose melting point is below that of the workpiece.

If the solder melts above 450°C the process is termed "hard soldering or brazing" and at lower temperatures "soft soldering". Apart from additional hazards due to the base material binders, the hazards involved in soldering are mainly associated with the flux and the solder.

The composition of a flux depends on the base material, the solder and the intended use. More than 300 different types of flux are currently available, all of which contain aggressive chemicals. Soldering paste usually contains colophonium, talc and salmiac, while soldering fluid contains zinc chloride or tin chloride. Chlorine and chlorine compounds cause irritation of the respiratory tracts and the skin and, in high concentrations, lung damage. Fluxes also frequently contain fluorine compounds (irritation of the respiratory tracts, burns). Fluxes often contain substances responsible for allergies. These are mainly colophonium and hydrazine. Hydrazine is additionally classed as carcinogenic.

Tin-based solders containing lead are used for soft soldering and silver solder containing cadmium for hard soldering. Flux vapours carry metal particles which can be inhaled.

Environmental protection measures to combat the emission of liberated gases and component substances of solders and fluxes include the installation of extractor systems with downstream separator filters (cyclone method). This method may also be used to contain the environmental impact of the production stage discussed in the next section.

2.1.7 Grinding

Grinding is the cutting of a workpiece with a geometrically undefined cutting process.

Grinding processes are characterised by high temperatures, workpiece removal and abrasive wear. In addition to noise, the health hazards from grinding are principally emissions from abraded dust or particles from the abrasive tool, workpiece and any coating, and - in the case of wet grinding - from coolants. There is an attendant risk of health disorders especially affecting the skin and respiratory tracts. Additives in coolants and the metal dusts produced (e.g. from chromium, cobalt, nickel or beryllium) can result in allergies. These metals may also be carcinogenic. The following table shows the potential pollutant sources when grinding metals.

Potential pollutant sources in the grinding of metals

Material-dependent Process-dependent

Grinding tool Formation of superfine dust with

- abrasive material - profiling and dressing of containing zircon grinding discs
- lead chloride, antimony - tool grinding sulphide in separating - fettling, due to adhering cutting in stationary operation mould residues
- additives in grinding - manual grinding, usually belts containing fluorine carried out without extraction ventilation

Coolant - coarse grinding additives, with respect to - use of magnesite binders toxicity, carcinogenicity and mutual reactivity

Material containing Combustion and pyrolysis

- more than 80% %/wt. products which can occur nickel (e.g. depositing with the thermal decomposition of materials) rubber or synthetic resin
- less than 80% %/wt. nickel (e.g. high grade corrosion-resistant steel)
- Lead (e.g. in automatic Accumulation of heavy metals and steel) superfine particles in coolant
- Cobalt (e.g. hard metal, co- due to inadequate filtration alloys) or overuse
- Beryllium (e.g. Ni Be alloys)

Atomization of coolant and thus also of additives, reaction products, dissolved heavy metals and superfine, non-separated particles.

Protective measures include environment-oriented selection of grinding tools, coolant and - where possible - materials, extraction of the abraded materials and personal breathing and hearing protection.

2.2 Mechanical engineering and operation of workshops and shipyards

Special environmental problems which are not found elsewhere arise in mechanical engineering, in workshops and in shipyards. This is because the work is not carried out in one location alone, and because pollutants are diffused and vaporised throughout the site. Estimation of their environmental relevance is difficult due to their often low concentration and they frequently seem harmless, so it is not easy to communicate the problem to workers and managers. Therefore environmental training measures should be taken into account as early as the planning phase. Much depends on the attitude in the workplace, the choice of working equipment and materials and the observance of worker protection measures. Planning must additionally include early integration of technical environmental protection measures (filter systems, wastewater collection installations, cleaning installations etc.).

2.2.1 Waste air

Environmentally relevant waste air flows can be released into the environment through forced ventilation (e.g. fan systems) and/or random emission13) from diverse areas of the site.

13) Emissions are defined as air impurities (gases, dusts), noise, radiation (heat, radioactivity etc.), vibration and similar phenomena given off to the environment by a (fixed or mobile) system.

These include emissions from:

- production extractor systems
- workplace extractor systems
- room air extraction
- production processes
- mechanical cutting
- thermal joining and parting (welding, cutting)
- joining (e.g. bonding, soldering)
- surface treatment (cleaning, coating, hardening and tempering)
- drying

Emissions into the air can be divided into:

- coarse and fine dust
- aerosols
- organic and inorganic gases and vapours

Harmful components of the waste air are essentially:

- organic solvents and halogenated hydrocarbons from metal cutting (coolants), cleaning, degreasing, bonding and painting of workpieces in the form of gases, vapours and aerosols
- dusts from the mechanical processing of materials

Whether or not cleaning of the waste air is an absolute necessity depends e.g. on the solvents in use, the presence of other contaminating operations, weather conditions etc., also therefore on ambient factors. Long-term risks for man and the environment may be posed even by relatively small workshops.

In the interests of worker protection, room air pollutants occurring in the production process must not exceed certain MAK values14). Where necessary work should be carried out in enclosed equipment. Efficient aeration and ventilation must be guaranteed, or pollutants must be extracted at the point of origin. Extracted flows of (pollutant) substances are to be cleaned by suitable processes before being expelled to the environment.

14) in Germany

Possible processes are:

· Dust separation:

Dust is a mixture of particles of different grain size, particle size depending very much on the process. Various processes are used for dust separation. These are classified as follows:

A: inertia separators (cyclone, "multiclone", mechanical separator)
B: wet type separators (scrubbers, wet separators)
C: electrical separators (dry and wet electrostatic filters)
D: filtering separators (fabric filters, cloth filters, bag filters, vibratory sheet filters and tubular filters).

· Aerosol separation:

Waste gases containing droplets are also termed aerosols and hence distinguished from dust-laden waste gases. Droplets can be separated using the same physical principles as for dust. The greater adhesion of the separated droplets compared with dust however rules out use of the principal dust separators such as electrostatic filters and filtering separators. Only wet separators, i.e. scrubbers and wet type electrostatic filters are suitable without modification for separating aerosols.

· Separation of vaporous or gaseous substances:

The principal methods for reducing emissions of gaseous inorganic and organic substances are absorption, adsorption and thermal processes. With absorption the gaseous air pollutant is absorbed by a washing fluid. Absorption is either physical or chemical, depending on whether the absorption is based exclusively on the solubility of the gas, or whether additional chemical reactions occur in the liquid phase. Absorption processes, and also thermal and catalytic processes, are used particularly for reducing levels of organic substances.

Water-soluble organic substances, e.g. methanol, ethanol, isopropanol and acetone can be effectively separated from waste gases through absorption by means of scrubbers. The contaminated washing fluid can normally be regenerated by fractionation15).

15) Fractionation is the separation of fluid mixtures by repeated distillation.

Separation of large amounts of solvents is done by the condensation process. Recently, biological processes such as biofilters or biowashers have also become popular for cleaning waste gases with highly odorous components and/or solvents.

Adsorption is the attachment or accumulation of foreign molecules on the surface of a solid (adsorbent). Regeneration of laden adsorbents is normally done by desorption of the adsorbed substances in the gas or liquid phase (so-called desorption phase), i.e. by reversal of the adsorption process. As the desorption phase (usually a gas) contains the substance removed from the waste gas in an enriched concentration, recycling or reprocessing is possible. Solvent recycling is an especially important area of application for the adsorption process. Adsorbents are mostly activated carbons.

The residual substances yielded by the separation of the solid and gaseous waste gas pollutants (filter dusts, scrubbing water residues etc.) are normally hazardous materials and must be disposed of as special waste (giving rise to waste problems). The price of solving emission problems is often soil and water contamination, and land may become so contaminated it will eventually have to be rehabilitated (see also the environmental brief Disposal of Hazardous Waste).

2.2.2 Wastewater

In mechanical engineering, the recycling of process materials from wastewater is frequently only possible with disproportionate technical effort or not at all, because of the low concentrations involved. Concentrated liquid and spent process and production materials can and must be collected and disposed of as (hazardous) waste.

Wastewater is returned to natural bodies of water (lakes, streams, rivers, sea) after preliminary and final cleaning. There, any inorganic pollutants will lead to poisoning and deposits. Organic impurities may also be toxic and/or non-degradable. Degradable, non-toxic waste substances damage the environment by initiating excessive growth (eutrophication) of bacteria and minute life forms (algae, fungi) due to the nutrient supply. In combination with cell metabolism, this results in high oxygen consumption and finally to phenomena such as the "overturning" of the water (anoxic waters).

Heavy metals mostly enter the wastewater as metal salts produced by chemical reaction of the metals with the acids. The acidic pH value which prevails in heat treating and pickling shops promotes the solubility of the heavy metals in wastewater and hinders their removal.

Heat treating and pickling shops rinse workpieces in fresh water prior to further processes. After use, pickling fluids also contain heavy metals. In electroplating operations, rinsing water contains cyanide and is polluted with the heavy metals which are used (depending on the type of surface finishing).

Halogenated hydrocarbons are insoluble in water. They mainly enter the wastewater via rinsing water after degreasing in surface treatment plants and when cleaning engines and other objects in motor vehicle and general workshops by the use of cold cleaners and pickling agents. Further emission sources are coolant carry-overs and losses, workpiece rinsing and workshop floor cleaning.

Organic solvents can enter the wastewater via absorption and spray cleaning processes. Mineral oils occur with the cleaning of workpieces and floors and degreasing, and through losses during processing. Emission sources are repair, motor vehicle, factory and maintenance workshops. In surface treatment workshops they occur in the form of the workpiece anti-corrosion and rust-protection oils used in preliminary cleaning.

Acids and alkalis enter the wastewater in pickling shops and heat treatment shops in connection with degreasing. Other wastewater burdens occur due to nitrogen (ammonium) and phosphor compounds (phosphates from pickling shops).

Wastewater can be cleaned by chemical, physical and biological processes or a combination of these. Three-stage purification of industrial wastewater is now generally considered the state of the art.

Only organic and non-toxic wastewater impurities can be removed biologically. Tests in the laboratory will determine whether or not the components contained in the wastewater inhibit biodegradability.

With biological processes a distinction is made between aerobes (with oxygen) and anaerobes (without oxygen). With high burdens (chemical oxygen demand (COD) in excess of 15,000 mg/l), anaerobic processes are used for preliminary cleaning before aerobes carry out the final cleaning, since otherwise the oxygen supply costs are excessive.

High-performance biological processes with high pollutant decomposition rates are now available to build small but nevertheless efficient systems. Newly developed processes are achieving success in the biological neutralisation of organic pollutants previously considered non-biodegradable, e.g. CHCs, by optimising the living conditions for special bacteria.

Flocculation/precipitation processes can be used to remove heavy metals from wastewater, also sedimentation processes in the case of undissolved wastewater. Chemical oxidation and precipitation processes can be used for the removal and de-toxification of cyanide.

Emulsions originating from the use of coolants can be separated by the membrane filtration process in conductive wastewater (approx. 90%) and concentrate.

Ultrafiltration is used with electrostatic immersion painting for the separation of solid paint residues. This is increasingly replacing simple sedimentation with the separation of undissolved pollutants in wastewater because it is more efficient, though more costly. Wastewater containing acids and alkalines must pass through neutralization systems. Ion exchange systems cannot selectively remove metals but are highly suitable for cleaning water carried in a circuit and recycling raw materials. For recycling pure raw materials, the different waters must be carried and used separately.

2.2.3 Waste matter

Waste matters generated by these plants can be divided into three groups:

A. Residues of the used raw materials. These include both ferrous and non-ferrous (NF) waste (scrap/chips and swarf) which may be highly contaminated with coolant, cutting oil and leaked lubricating oil.

B. Waste from process residues resulting from the processing of semifinished products and auxiliary materials. Metalliferous residues are e.g. burnt slag from torch cutting, metal sludges, used salt and acid baths from electroplating or pickling shops.

C. Non-metalliferous waste can be paint and adhesive residues, oil and oily waste, organic acids, alkalis and concentrates. Finally, waste may also be produced by wastewater and waste air cleaning processes. These include purification sludges from the works’ own sewage treatment plant plus dusts and sludges from the cleaning of waste air and extraction flows in the form of filter residues.

Nearly all waste in the second and third groups can be regarded as hazardous waste. They demand special monitoring and special disposal methods. Waste from the first group should mostly be recycled. Separate collection of scrap types (structural steel, alloyed steel, NF metals) in different containers is important for simple and comprehensive recycling.

In order to reduce scrap quantities with torch cutting and punching, care must be taken to achieve a systematic geometrical arrangement of contours on the sheet metal. Recycling should be considered where there are high concentrations of costly raw materials in liquid or sludge waste. To reduce waste further, fluids should where possible be cleaned with filters or baths regenerated.

2.2.4 Soil

The effects on the soil can be problematic in terms of both quality (e.g. toxicity or persistence) and quantity (e.g. acidification or leaching). Airborne emissions are normally small in quantity, therefore the main causes of pollution are the discharging of residual and waste materials (filter dusts, washer and scrubber residues, purification sludges) and improper handling of auxiliary materials. Of the large number of chemical substances used in metal processing, only a few substance groups have to be regarded as representing a soil hazard and thus in general also a groundwater hazard:

- anions (chlorides, sulphates, ammonium, nitrates, cyanides etc., produced e.g. in heat treatment and pickling shops)
- heavy metals (lead, cadmium, chromium, copper, nickel, zinc, tin etc.).
- solvents (halogenated and pure hydrocarbons)
- other oil-containing substances

The areas in which contamination occur are:

- all production stages using the named substances
- storage of new and used chemicals
- transport, loading and unloading on the works site (containers, tanks, pipelines, extraction system)
- cleaning and repair processes.

To protect against contamination in these areas, the ground must be "sealed" (i.e. provided with a protective layer to prevent penetration of the materials into the ground, or with pollutant collection devices, e.g. containment basins). Insufficient attention is often paid to the storage of hazardous materials. This can result in severe environmental pollution with long term consequences, also and in particular for third parties (e.g. due to groundwater pollution). Containers and pipelines used for transporting the materials are to be regularly checked for leaks. Care must be taken to ensure an efficient flow of work and materials, with clear rules on the depositing and disposal of waste/residues (see environmental brief Disposal of Hazardous Waste, also the reference literature).

2.2.5 Noise

Deafness and loss of productivity result from noise pollution above a certain level. A noise level in the workplace of around 85 dB(A) or higher for the greater part of the working shift, over a number of years, is regarded as detrimental to hearing16).

16) It is as harmful to be exposed constantly to a uniformly low noise level as to a higher one for a short time.

For comparison: Leaves blown by a light wind emit a noise level of 25 to 35 dB(A); normal conversation is between 40 and 60 dB(A). Note also that the medium and higher frequencies between 1,000 and 6,000 Hz are the most damaging.

When considering noise immissions17), a distinction must be made between the direct effect on workers at the workplace and the indirect effect due to radiation and immission in the environment. In assessing noise therefore, three aspects, each requiring different reduction measures must be considered.

17) The term immission is the effect of air impurities, radiation (e.g. thermal radiation) on man, animals, plants and property.

A. Noise origination
B. Noise propagation

· Noise transmission (propagation of sound waves in different media, e.g. transmission of machine vibrations to foundations);

· Noise radiation (stimulation of air vibrations by solid-body vibrations - loudspeaker diaphragm principle).

During operations in this sector, noise is generated by machinery, by hammering, nailing, or chipping, by internal transportation processes, impact upon depositing or lifting of semifinished products, air and gas movements, fan outlets, pneumatic components, cutting torches etc.

A fan, e.g. with 50 kW, 970 rpm and a diameter of 1,800 mm, without noise damping produces a noise level of 100 dB(A). A compressed air jet produces a noise level of 108 dB(A) with an air pressure of 5 atmospheres. Welding and cutting generate noise levels of up to 101 dB(A) and pneumatic riveters and chippers produce between 100 and 130 dB(A). Manual grinders develop up to 106 dB(A). Metal band saws develop up to 106 dB(A). Turning generates between 80 and 107 dB(A). Screw presses produce noise levels up to 103 dB(A).

Noise pollution in the neighbourhood of a factory is mainly caused by radiation through the walls of the production sheds and buildings and by outward blowing fans.

Structural measures to reduce noise should therefore be taken into account as early as the planning phase (noise-absorbing walls, choice of windows, type of building materials etc.). The expected noise conditions cannot be determined simply by adding together the known noise levels of the planned machines and processes. Due to interaction and the different damping and reflection circumstances, only on-site measurements can yield accurate data on noise conditions. The maintenance of adequate distances reduces the effect on the neighbourhood.

With regard to noise protection, a distinction is made between primary and secondary measures. Active primary measures signify the use of machines constructed according to low-noise principles. For example, sheet metal forming can be made quieter by replacing impact methods with hydraulic pressing. Priority should be given to the implementation of active primary measures.

Active secondary measures are sound insulation (prevention of propagation by obstacles) and sound absorption (absorption of sound energy and its conversion to heat). A distinction is made between structure-borne and airborne noise:

- Insulation of airborne noise is achieved by partition walls, full or partial enclosure, cladding or screening.
- Insulation of structure-borne noise can be achieved by machine feet of elastic material which prevent the transfer of vibrations.
- Absorption of airborne noise over large areas can be achieved with sound-absorbing cladding material of foam or glass fibre matting. Silencers should be fitted to reduce noise at gas and air outlets. Composite silencers combining an absorber and a resonator should be provided for dust-laden gases.
- Absorption of structure-borne noise damping is achieved by means of soundproof coverings in the form of foam rubber mats on sheet metal or in sandwich form (metal - covering - metal).

Passive noise protection signifies all equipment and measures for preventing the immission of noise and vibration to the environment and the human ear. These include personal ear protection, noise protection for control rooms, noise-insulated cabins etc.

Workers must wear ear protection in the workplace where noise levels are higher than 90 dB(A). Such workplaces must display suitable warning signs; the observance of protective measures must be monitored.

Proven methods of reducing noise immissions include the use of soundproof walls or partitions and increasing the distance between industrial buildings and residential areas. With uninhibited propagation the acoustic power level is reduced by 3 (house wall) or 6 (point source of noise) dB(A) by doubling the distance.

3. Notes on the analysis and evaluation of environmental impacts

This section describes underlying reference material which, unless otherwise indicated, refers to the situation prevailing in Germany. Obviously these rules cannot be applied wholesale to other countries without modification. The material is intended at least to serve as a reference where no national regulations are available. The INFOTERRA National Focus Points of the UNEP are a valuable source of information. These contain environmental information records for the member state in question. The reference service is free of charge. The Environmental Guidelines of the World Bank are an important source of application-related information, e.g. for dust emissions, waste matter and wastewater.

The Catalogue of Environmental Standards (Vol. III of this Environmental Handbook) also deserves special mention. This lists standards and limits for assessment purposes.

Regulations on the protection of persons from danger and injury in the workplace (worker safety, industrial medicine) are contained in the Unfallverhvorschriften der Berufsgenossenschaften (accident prevention regulations of the employers’ liability insurance associations) and in their other publications such as "Sicherheitsregeln" (safety regulations) and "Richtlinien" (guidelines). Also worthy of note are the Occupational Health and Safety Guidelines of the World Bank and the Encyclopedia of Occupational Health and Safety of the International Labour Organisation (ILO).

3.1 Air

TA-Luft (Technical Instructions on Air Quality Control) regulates the technical standards concerning pollutant emissions and immissions for installations subject to licensing.

The guidelines on maximum immission concentrations (MIK) published by the Association of German Engineers (VDI) lay down limits for certain air pollution levels. These are defined as the concentrations in the ground-level open-air atmosphere or in dust and the quantities precipitated on the land below which man, animals, plants and property are guaranteed to be safe according to the present level of scientific knowledge (see also reference to MAK values).

Also of importance are the EC Directives on sulphur dioxide and suspended particulates, lead and nitrogen dioxide (EC Directives 80/779/EWG, 82/884/EWG, 85/203/EWG), also the WHO Air Quality Guidelines for 28 chemicals on the basis of toxicological findings.

3.2 Wastewater

Discharge conditions for wastewater are laid down in the Wasserhaushaltsgesetz (Federal Water Act), the Abwasserangabengesetz (Wastewater Charges Act) and the associated Verwaltungsvorschriften (administrative regulations). These prescribe limits of individual pollutants for different sectors.

Annex 40 currently applies to metalworking and processing with direct discharge (discharge into bodies of water). This gives details of the maximum concentrations for COD18), BOD19), heavy metals, hydrocarbons, ammonium, phosphorous and halogenated hydrocarbons.

18) COD: Chemical Oxygen Demand
19) BOD: Biological Oxygen Demand

The limits for indirect discharge (discharge into waste-water purification plants) for COD and substances classified as non-hazardous are less strict. The limits for indirect discharge are detailed in the ATV work sheet Arbeitsblatt A 115 according to sectors. This work sheet is currently being adapted to the new wastewater management regulations.

For their projects the World Bank stipulates that the temperature of discharged wastewater must be no more than 3°C higher than that of the receiving body of water. If the temperature of the receiving body is 28°C or less, the temperature of the discharged wastewater must be no more than 5°C above that of the receiving water.

3.3 Waste matter

The definition of waste types according to Section 2 of the Abfallgesetz (Waste Avoidance and Waste Management Act) for the metal working and processing industry is contained in the Verordnung zur Bestimmung von Abfen (Regulation on Waste Definition). A further designation of waste types according to code numbers is contained in the publication on waste types of the German state working group on waste Landesarbeitsgemeinschaft Abfall (LAGA). Of relevance here are waste groups 35 (metal waste), 51 (oxides, hydroxides, salts) with electrolytic sludges, 52 (acids, alkalis, concentrates) with waste from surface treatment, 54 (mineral oil products) and 55 (organic solvents, paints, lacquers, adhesives, cements and resins). For electroplating and painting, refer to the regulation on waste identification Abfallnachweis-Verordnung. For motor vehicle and general workshops, see the regulation on waste oil Altrordnung.

For the use and handling of special waste, refer to the three-volume edition of "The Safe Disposal of Hazardous Wastes" and the manual "Techniques for Assessing Industrial Hazards", both published by the World Bank; also the environmental brief Disposal of Hazardous Waste.

3.4 Noise

Accident prevention regulations are published by the employers’ liability insurance associations or Berufsgenossenschaften, and these deal with the protection of workers from noise in the workplace. The noise protection and information sheets of the Hauptverband der gewerblichen Berufsgenossenschaften, are important publications in this regard. The Association of German Engineers (VDI) has issued numerous regulations and directives concerning noise in the workplace, the impact of noise on the environment and noise protection measures. Guidelines on noise protection for installations subject to licensing (according to the implementing ordinance of the Federal Immission Control Act) and neighbourhood immission guidelines are contained in TA-L (Technical Instructions on Noise Abatement).

4. Interaction with other sectors

Mechanical engineering and the production of semifinished products for machinery in other sectors represent a highly diversified capital goods industry, so there is often close interaction with other sectors. Interaction is not necessarily regional, on account of the high specific added value, therefore interacting environmental problems do not occur generally but rather in individual cases.

With mechanical engineering works, workshops and shipyards of a certain size, attention must be paid to the effects on infrastructural sectors. In this regard see the environmental briefs Spatial and Regional Planning, Planning of Locations for Trade and Industry, Overall Energy Planning, Water Framework Planning, Urban Water Supply, Rural Water Supply, Wastewater Disposal, Solid Waste Disposal, Transport and Traffic Planning, Road Building and Maintenance - Building of Rural Roads, Road Traffic, Railways and Railway Operation, Inland Ports, Shipping on Inland Waterways, Ports and Harbours - Harbour Works and Operations, Shipping, River and Canal Engineering.

There may also be an interaction with sectors covered in the following environmental briefs Surface Mining, Underground Mining, Minerals - Handling and Processing, Power Transmission and Distribution, Iron and Steel and Non-ferrous Metals.

5. Summary assessment of environmental relevance

The aim of this environmental brief has been to summarize the environmental relevance of mechanical engineering works, workshops and shipyards. Detailed investigations are to be made in each specific case as to the possible environmental hazards. Even small environmental problems which appear at the outset to be of marginal importance can, in certain contexts, result in failed projects or serious damage. Countermeasures must be integrated into the planning and execution at an early stage. From the point of view of environmental protection, mechanical engineering should involve a combination of precautionary measures and appropriate management decisions. Therefore training in environmental protection must be given high priority in every project. Workers should be trained in occupational safety and environmental protection. The management should be familiar with and apply additional precautionary measures (knowledge of suitable pollutant disposal methods or plant optimization with a view to environmental protection, e.g. choice of paints/solvents with low pollutant contents).

An important further precondition of applied environmental protection is the existence of effective waste disposal facilities, especially for problematic hazardous waste. Technical staff must also be on hand, e.g. to maintain filtration and wastewater treatment plants, the erecting and operation of which are described in the present brief.

6. References

Abwassertechnische Vereinigung (ATV) (Ed.): Lehr- und Handbuch der Abwassertechnik, Bd. I - VI, Ernst Verlag, Berlin, various years.

Abwassertechnische Vereinigung (ATV) (Ed.) Arbeitsblatt A 115, Hinweise f Einleiten von Abwasser in eine ntliche Abwasseranlage, draft of 22.03.1990.

40. Anhang zur Allgemeinen Rahmen-Verwaltungsvorschrift indestanforderungen an das Einleiten von Abwasser in Gewer, GMBI. (joint ministerial circular) 1989, Nr. 25, p. 517 ff.

Batstone R. et al.: The Safe Disposal of Hazardous Wastes, The Special Needs and Problems of Developing Countries, Vol. I, II, III, World-Bank Technical Paper No. 93, Washington, 1989.

Brauer, H.: "Die Adsorptionstechnik - ein Gebiet mit Zukunft", Chem.-Ing.-Tech. 57, (1985), Nr. 8, p. 650 - 663.

Deutsche Forschungsgemeinschaft (DFG) (Ed.): Kmierstoffe, Liste von Komponenten, in: Toxikologisch-Arbeitsmedizinische Begr von MAK-Werten, Weinheim 1983.

DIN 45635: Gerchmessungen an Maschinen.

EC Council Directive on sulphur dioxide and suspended particulates, lead and nitrogen dioxide (EC Directive 80/779/EWG, 82/884/EWG and 85/203/EWG).

Fischer, H. et al.: "Galvanotechnik", in: Ullmanns Enzyklope der technischen Chemie, Band 12, p. 137 - 203, 76th year.

Geretzki, P.: "Erkrankungen durch Kmierstoffe in der Metallindustrie", in: Dermatosen 31, 1983, Nr. 1, p. 10 - 14.

Gesetz bgaben f Einleiten von Abwasser in Gewer (Abwasserabgabengesetz -AbwAG, BGBl. I (Federal Law Gazette I), p. 2432, 1990).

Gesetz zur Ordnung des Wasserhaushalts (Wasserhaushaltsgesetz - WHG, BGBl. I (Federal Law Gazette I), p. 205, 1990).

Gewerbliche Berufsgenossenschaften, Unfallverhvorschriften: VBG 7, VBG 15, VBG 23, VBG 24, VBG 57, VBG 113.

Hser, M., et al.: Kmiermittelbestandteile und ihre gesundheitliche Wirkung", in: ZbC. Arbeitsmed., 35, 1985, Nr. 6, p. 176 - 181.

Hartinger, H.: Handbuch der Abwasser- und Recyclingtechnik f metallverarbeitende Industrie, Munich, Vienna, 2. Auflage 1991 (Carl Hanser Verlag) ISBN 3-446-15615-1.

Hauptverband der gewerbliche Berufsgenossenschaften e.V.:

ZH 1/81 Merkblatt fliche chemische Stoffe

ZH 1/194 Merkblatt forkohlenwasserstoffe

ZH 1/425 Kaltreiniger-Merkblatt

ZH 1/562 Sicherheitsregeln fagen zum Reinigen von Werkstmit Litteln (Littel-Reinigungsanlagen)

ZH 1/566 Merkblatt flosionsschutzmaahmen an Littelreinigungsanlage

Other ZH 1 publications.

Hauptverband der gewerblichen Berufsgenossenschaften e.V.: Lschutz-Arbeitsbler und Lschutz-Informationsbler.

Koenigs, M.: "Schweierfahren, Gefdungen und Schutzmaahmen", BAD-intern 2/83.

K, W., et al.: Schadstoffe beim Schleifvorgang, Schriftenreihe des Bundesanstalt feitsschutz, Forschungsbericht 427, Dortmund 1985.

Air Quality Guidelines for Europe, WHO regional publications European series: No. 23/1987.

Mahler, W., Zimmermann, K.F.: "Aktuelle Hinweise zur Einhaltung der verschten Arbeitssicherheits-und Umweltschutzbestimmungen beim Verarbeiten cadmiumhaltiger Hartlote", in: Schwein und Schneiden, 1986.

Mannheim: "Sicherheitsmaahmen bei der Verwendung von Halogen-Kohlenwasserstoffen bei der Metallentfettung", in: sicher ist sicher 7/8, 1983, p. 333 - 338.

Maschinenbau- und Kleineisenindustrie-Berufsgenossenschaft, Kampf dem Arbeitsl 3, Lminderung friebspraktiker, 1983.

Maschinenbau- und Kleineisenindustrie-Berufsgenossenschaft: Broschmierstoffe", January 1991.

Menig, H.: "Luftreinhaltung durch Adsorption, Absorption und Oxidation", Deutscher Fachschriften Verlag, Wiesbaden 1977.

Ministerium fung, Landwirtschaft, Umwelt und Forsten, Baden-Wberg, Altlasten-Handbuch Teil 1, Stuttgart 1987.

M R.: "Arbeitssituation und gesundheitliche Lage von Schweirn", Forschungsbericht Nr. 252 der Bundesanstalt feitsschutz und Unfallforschung, Dortmund.

Muster-Verordnung nlagen zum Umgang mit wassergefdenden Stoffen und achbetriebe der Lerarbeitsgemeinschaft Wasser (LAWA), draft of 31.08.1990.

Rosenkranz, D., Einsele, G., Harre H.M. (Ed.): in: Bodenschutz-Handbuch, Erich Schmidt Verlag, Berlin 1988.

Sch.: "-Aerosole an industriellen Arbeitsplen", in: Staub RL 44, 1984, Nr. 6, p. 268 - 272.

Seebohum, K.W.: "Beurteilung von Schweirbeitsplen", in: sicher ist sicher - Zeitschrift feitsschutz, 9/85, p. 454.

Szedkowski, D.: "Gesundheitsgefahren durch Littel", in: WBau BG, Mitteilungen 2/1985, p. 25 - 27.

TA-Luft, Technische Anleitung zur Reinhaltung der Luft of 27.02.1986, GMBl. (joint ministerial circular),p. 95 ber. p. 202.

TA-L, Technische Anleitung zum Schutz gegen L of 16.07.1968, annex to Federal Law Gazette (BAnz.) No. 137 of 26.07.1968.

Technica, Ltd.: Techniques for Assessing Industrial Hazards, A Manual, World Bank Technical Papers No. 55, Washington, 1988.

Umweltbundesamt (Federal Environmental Agency (Ed.)): Handbuch Abscheidung gasfger Luftverunreinigungen, Erich Schmidt Verlag, Berlin 1981.

Umweltbundesamt (Federal Environmental Agency (Ed.)): Branchentypische Inventarisierung von Bodenkontaminationen, Forschungsbericht 03001, Berlin 1986.

VDI (Verein Deutscher Ingenieure): VDI-Handbuch Reinhaltung der Luft, Beuth Verlag, Berlin and Cologne.

VDI (Verein Deutscher Ingenieure): Technische Sorptionsverfahren zur Reinhaltung der Luft, VDI-Bericht 253 (1975).

VDI (Verein Deutscher Ingenieure): Abgasreinigung durch Adsorption, Oberflenreaktion und heterogene Katalyse, VDI Richtlinie 3674.

VDI (Verein Deutscher Ingenieure): VDI-Richtlinien zur Gerchmessung, Schallschutz, Schwingungstechnik: 2560, 2564, 2567, 2570, 2571, 2711, 2714, 2720, 3727, 3749, 3731, 3742.

Verordnung ie Herkunftsbereiche von Abwasser of 03.07.1987, BGBl. I (Federal Law Gazette I), p. 1529.

Zschiesche, W., et al.: "Neue Erkenntnisse zur Berufspathologie der Schweir", Arbeitsmed., Sozialmed. Prntivmed. 20 (1985), p. 140 ff.

1. Scope

The agro-industry is based on agricultural and forestry production, and its purpose is to preserve and refine raw produce and to extract and concentrate the valuable constituents. The food industry constitutes the most important sector of the agro-industry.

Many agro-industries have developed from skilled manual production processes and accordingly can be carried out at varying technical levels. The following information, however, applies to small and medium-sized operations. The definition of small and medium-sized operations varies from country to country but a maximum of 100 employees can be taken as an upper limit. There are environmental briefs which focus specifically on a number of agro-industries, particularly large plants.

In no other area are development and environment so closely intertwined as in that of the agro-industry. Unforeseen implications can turn intended impacts on their head, and medium and long-term damage may prove to be of short-term benefit. Nowhere are effects on the biosphere -including human society - so all-embracing as in the agro-industry. And no other sector is so dominated by female employment; all the activities in this sector are of major importance to and have major effects on women. All agro-industry activities depend essentially on the limited time women have available, their extensive responsibility and on limited water and energy resources. This is why the socio-economic parameters and influences are priority issues in agro-industry projects.

A distinction can be made within the agro-industry between primary, secondary and even tertiary processing. Primary processing is basically most suited to small industrial operations, as technical input increases in line with processing complexity.

2. Environmental impacts and protective measures

2.1 The agro-industry generally

As the agro-industry will probably increase the demand for certain commodities, or alternatively push towards different forms of land use and farming, the following environmental impacts in the area of agricultural production should be mentioned:

Problems relating to the direct expansion and intensification of resource usage include impairment of soil fertility, problems of soil losses and sedimentation, problems of desertification and irrigation problems (soil and water salination, fluctuating water table and water pollution), which in turn reduce resource productivity. The problems of fertility losses, desertification, and salination are generally greatest in countries where the population pressure on land is greatest. Here, agriculture expands most markedly in peripheral areas and marginal resources are utilised intensively.

The most successful efforts lie in the promotion of soil-conservation measures: reducing the intensification of soil usage, and introducing programmes for minimum or soil-conservation farming (contour line farming, terrace farming, strip farming, extension of dry and green fallow land), programmes to control flooding and wind erosion and programmes for the improvement of crop rotation. What needs to be examined is the extent to which these measures should be implemented as an alternative or in addition to the establishment of agro-industrial production operations.

The economic and social parameters in place and those sought are decisive factors in the agro-industrial sector generally. The maintenance and promotion of subsistence production and agro-industrial activities without restricting subsistence are major axioms in this respect.

Commodity processing gives rise to environmental impacts on the atmosphere (odours and dust emissions), water (quantity and wastewater), primary energy sources (mainly timber) and the soil.

The following comments are confined to certain branches which have been in the greatest demand in recent years.

2.2 Selected branches

2.2.1 Mills handling cereal crops

Only dry milling is carried out in such plants, thus account must be taken of noise and dust emissions which affect not only the specific operational area but also the area surrounding the mill. Suitable countermeasures are technical installations (extraction, soundproofing) and individual measures (breathing apparatus, hearing protection), priority being given to the first group, since the use of individual safety equipment requires explanatory and supervisory measures.

Surface water quality is impaired in cases where streams and rivers are used for waste disposal, for example. Further usage or controlled dumping are suitable countermeasures (cf. environmental brief Mills Handling Cereal Crops).

2.2.2 Processing of starch sources and root crops

If the biologically polluted wastewater from washing and processing is discharged into surface water untreated, the result can be overfertilization, reduction in the oxygen content and therefore a general impairment of water quality, changes in the micro flora and fauna and, in the medium term, disruption of water biotopes.

Appropriate minimum measures are mechanical separators and aeration ponds in which the biological oxygen demand is reduced to an acceptable level. Since a reduction in the biological pollution of wastewater is associated with improved yield, optimised process technology can also be an economically beneficial environmental measure. Finally, highly polluted wastewater which can normally be avoided where a process is appropriately optimised, can be used as a substrate for biogas production.

2.2.3 Processing of oil-bearing seeds and fruits

In small and medium-sized works, only pressing processes are used for oil extraction, with solvent extraction reserved for large plants (see also the environmental brief Oils and Fats). Oil-bearing fruits are heated directly or with steam or hot water to improve yields. This produces steam emissions and oil-laden wastewater. Wood is often used for energy production, and this can lead to over-use of tree stocks.

Because steam emissions affect mainly operating personnel extraction should take place at the point of production. Once again, process optimisation, the use of better separators and treatment in aeration ponds should be used to reduce wastewater pollution. Consumption of wood or other commercial fuels can be reduced by incinerating the waste produced in the processing operations and also by optimising energy circuits and consumption in the processing plant.

2.2.4 Sugar beet and sugar cane processing

The essential environmentally relevant aspect of beet and cane processing is the energy required for the concentration of the sugar solution. While this requirement can be met in cane processing by burning bagasse, energy consumption in sugar beet processing must be optimised and, if necessary, alternative energy sources must be identified.

Mention should also be made of organically polluted wastewater from purification and condensate.

There is an environmental brief specifically relating to Sugar.

2.2.5 Fruit and vegetable processing

Biologically polluted washing water and the energy requirement for thermal preservation processes are of environmental relevance in this area, and the same comments as in the previous sections apply. Solar driers can also be used, thereby reducing the energy required for the production of top quality dried products quite considerably.

2.2.6 Dairies

As milk and dairy products are ideal breeding grounds for microorganisms, hygiene requirements are relatively stringent, a factor which prompts the use of aggressive cleaning agents. If they are discharged at certain concentrations, the quality of surface water is impaired and micro flora and fauna are affected.

Countermeasures are the sparing use of biodegradable cleaning agents and dilution in tanks.

Mention should also be made of percolating milk in rinsing and washing water as a source of organic pollution.

2.2.7 Processing of semi-luxury goods and spices

The operations having the greatest environmental relevance in the production of semi-luxury goods and spices are fermentation and waste disposal. Fermentation is generally carried out in fixed locations, and the pollutants thereby produced can accumulate in the soil over long periods, damaging micro flora and fauna. The washing operations sometimes carried out after fermentation (e.g. coffee) give rise to biologically polluted wastewater which, if discharged untreated, can impair surface water quality. The impacts of this are restricted to harvest time, and are then found over longer intervals.

Fermentation should be carried out in the immediate vicinity of an abundant supply of running water at appropriately prepared places (cement bases). The heavily polluted wastewater produced must either be suitably diluted before discharge or used for biogas production. As washing water is not generally so heavily polluted, special measures (aeration ponds) are only required in exceptional cases. Spices are often irradiated as a method of preservation, although the consequences of irradiation on human health are as yet unknown.

2.2.8 Plant fibre extraction

In many countries, microbiological retting is practically the only method of plant fibre production in use. It involves the degradation of non-fibrous components by a microbiological process and is carried out by immersing the raw material either in a slow flow of water or in specially prepared tanks, whereupon the retting is spontaneously initiated. Since this process and the subsequent fibre washing require large quantities of water, these installations are always built close to abundant supplies of running water. In these circumstances, the water exchange required once the retting process is complete is no problem (except perhaps for any dissolving pesticides used during farming).

The retting process is associated with a certain odour nuisance which cannot be avoided at reasonable cost. The only remedy is not to site these plants close to residential areas and to take account of prevailing wind directions.

Because fibre production is a low-input technology in every respect, negative environmental effects can only be avoided by selecting a suitable site and making use of what nature has provided.

2.2.9 Tanneries

Of all the agro-industries tanneries harbour the greatest risk potential for the environment. This is due on the one hand to the considerable odour nuisance and on the other to the dyes and other chemicals (particularly chromium compounds) used in the tanning process which complicate the wastewater treatment operation. And there is also biological pollution. Besides a substantial impairment of the quality of the nearby surface waters, an enrichment of the hazardous substances in the soil, and possibly also in the groundwater must also be expected.

The elimination of odours at source is only possible if the tanning is carried out in enclosed rooms and any air escaping is cleaned in technically sophisticated filter systems. The nuisance can be limited indirectly by concentrating plants of this kind on sites a suitable distance from residential areas. This would also create the conditions essential for the relatively complex process of multistage wastewater treatment, which is essential in this industry but which is really too costly for an individual small plant (see also the environmental guidelines of the World Bank).

2.3 Socio-economic impacts

The overwhelming majority of jobs in the agro-industry call for little in the way of qualifications and most workers are women. However, as mechanisation and machine-based jobs increase, the proportion of male workers rises - as do monotony and isolation of the individual working processes, and the risk of accidents. The extent to which the employment of women leads to changes in their own food production needs to be examined. The jobs are of poor quality in ergonomic terms, and nuisances in the form of dust, damp, smells and noise may attain levels which can affect the health of employees, constituting a considerable risk to women in particular. Because different types of jobs are done by the two sexes, qualification and training programmes must be established at an early stage, with the emphasis on female employment. These programmes should take account of the overall form of production and lifestyle of female employees and their families.

3. Notes on the analysis and evaluation of environmental impacts

The environmental impacts in the agro-industry can be assessed in terms of space, time and in relation to various resources and employees.

In the "agro-industry" sector assessments are based directly or indirectly on the following test criteria:

- impacts on employees in the factory
- impacts on people living near the factory
- environmental changes due to the emissions from the factory
- environmental changes caused indirectly by the factory (e.g. change in the quantity of water or extra energy required).

Short-, medium- and long-term impacts and likewise direct and indirect impacts must be considered in the light of these test criteria.

The evaluation involves comparing the project with other possible projects, and also considers the economic, ecological and social costs involved.

The evaluation of effects on health faces the problem of the frequent lack of national limits or recommended values for individual substances, and this is further complicated where a number of substances are emitted at the same time, thereby increasing their impact due to synergistic effects. One initial approach to this problem area may be provided by publications of international organisations such as the World Health Organisation (WHO) (see in this regard Volume III, Compendium of Environmental Standards.

4. Interaction with other sectors

There are close links with the plant and animal production sector which supplies the raw materials, and with the marketing sector, not forgetting the metal and mechanical engineering industries which manufacture the processing equipment, and the packaging materials industry.

Other factors in the equation are veterinary services, livestock farming, irrigation and health and nutrition. Projects in the field of the economy and also infrastructural measures, particularly in the rural hydraulic engineering sector, are significant issues in the assessment of agro-industrial projects, while cross-sectoral concepts of general resource management, location planning and regional planning must not be forgotten.

5. Summary assessment of environmental relevance

Agro-industries often serve as pilot projects for more general industrialisation, and must therefore be examined very closely in terms of their direct and indirect impacts on the food supply and economic prospects of the country concerned, its general environmental conditions, and the lives of its female population in particular.

Agro-industrial projects are extremely important to a country's independent development and this is closely allied to general subsistence production.

Direct environmental pollution from small and medium-sized agro-industrial factories on an individual level is relatively slight in the short-term, but the more general effects can be quite considerable.

One exception to this is tanneries because of the chemicals used -which are problematic in environmental terms - and the odour nuisance.

All factories which use water as the extraction, cleaning and transport medium produce wastewater which is biologically polluted to varying degrees, and this generally requires treatment in aeration ponds or treatment plants. Noise and dust emissions are normally restricted in terms of the area affected, and therefore affect primarily the employees themselves.

6. References

Bundesimmissionsschutzgesetz BImSchG of 15.03.1974.

Environmental Guidelines, The World Bank, Environment Department.

TA-Luft 27.02.1986.

TA-L 1968.

Verwaltungsvorschriften to § 7a WHG, Mindestanforderungen an das Einleiten von Schmutz- bzw. Abwasser in Gewer.

1. Scope

This sector embraces slaughterhouses, meat-processing plants and animal carcass disposal plants.

To date no standard project types have gained prevalence for slaughterhouses, particularly in terms of size, as each project is dependent on a a number of factors, such as:

- regional population density;
- specific consumption (kg/person and year);
- animal stocks in the region, catchment area;
- distance from nearest slaughterhouse;
- export potential, restrictions;
- eating habits;
- religious constraints.

Nor is there a standard size of meat-processing plant, as their design is also influenced by these same factors.

Animal carcass disposal plants (ADP) process dead animals, confiscated carcasses (where the meat or organs of slaughtered animals is found to be unfit for human consumption), blood, bones etc., the end products of which are - depending on the raw material - technical fats and meat meal, bone meal, blood meal etc., used for fodder and in some cases as fertilizer. Project size is determined primarily by the capacity of the neighbouring slaughterhouse.

For reasons of hygiene, cattle are hung for slaughter. The slaughter line feed system is manual in small operations and mechanical in plants with a medium or large line capacity.

Different processes are used in the bleeding stage, for example, since animals must be hung for bleeding to comply with EC Guidelines, but laid flat ("bleeding with the neck pointing to Mecca") in accordance with the dictates of Islam. (Sheep and camel slaughter similar to cattle slaughter).

Pigs can be slaughtered either hung or lying. A number of processes have been developed for the scalding and skinning of pig carcasses (scalding tank and depilation machines, production line systems where the animals are suspended or laid flat) depending on line capacity. Ritual slaughter is carried out for export.

Sheep are hung for slaughter and a number of methods are used for bleeding.

Because of the large number of different meat and sausage products, a wide range of processing stages20) are required. However, the following can be regarded as basic operations for all products:

20) for the processing of raw products and by-products.

carcass splitting - grinding of meat - seasoning - filling of natural or synthetic skins with sausage meat - heat treatment - cooling - dispatch - long-life meat products - tinned food.

The various processes used in the manufacture of meat and sausage products depend on the particular meat and sausage products in question, with processing carried out within different temperature ranges:

- uncooked sausage process temperature approx. 14 -28°C
- cooked sausage process temperature approx. 50 - 80°C
- tinned meat and sausage products process temperature approx. 80 -121°C

In animal carcass disposal plants, the material used and the waste material is largely processed by the pressing process following heating.

The extraction process is rarely used today because of the residues it leaves in the meal.

Fig. 1 - Flow chart of slaughterhouse

Fig. 2 - Flow chart of slaughter procedure

Fig. 3 - Flow chart of a meat product factory

Fig. 4 - Flow chart of ADP press installation

2. Environmental impacts and protective measures

Meat industry facilities cause environmental impacts due to:

- wastewater;
- spent air/waste gases;
- noise;
- animal waste;
- waste heat;
- residues in the end product;
- waste.

German regulations relating to environmental pollution caused by meat processing are taken as the reference in the following as they have also gained acceptance as the international standard.

Table 1 - Environmental impacts from meat industry plants

Type of plant	Waste-water	Odour	Waste gases	Noise	Waste	Waste heat
Fattening and breeding operations Slaughterhouses Recycling plant Meat-product factories	X X X X	X X X X	X X X X	X X X X	X X X	X X X

2.1 Water pollution

Water consumption and the degree of contamination of the wastewater arising from the process depend on a number of factors, and are determined principally by the following:

- species of animal;
- type and capacity of plant;
- intensity of cleaning of carcasses and
- working accommodation during the process.

The following values apply for slaughterhouses (average values):

- cattle 600 - 800 l/animal
- swine 300 - 500 l/animal
- sheep 200 - 300 l/animal.

Water consumption in meat-product factories is largely product dependent. Wastewater pollution is higher, for example, in plants producing mainly cooked sausage and tinned products than in those which, for example, produce only uncooked sausage (salami). Consumption is around 10 - 15 m3 per tonne of sausage and meat products.

Water consumption in ADPs is relatively low. The quantity of wastewater produced depends on the quantity processed, as some 65% of the raw material must be evaporated. On average, the wastewater level is approximately 1 m3/t raw material.

The degree of water pollution in the meat-processing industry is extremely high, particularly in slaughterhouses and ADPs. In Germany, the following minimum requirements on the discharge of dirt or wastewater into watercourses must be observed by the meat industry to prevent water pollution.

Table 2 - Degree of pollution of wastewater

Type	BOD5 valuemg/l	Causes and factors of influence
Slaughterhouses Meat-product factories ADPs	approx. 4,000 approx. 10,000 approx. 10,000	Some blood, content of stomach and intestinal tract, urine, liquid manure, animal waste etc. Animal waste, type of processing (boiling and steaming of raw material and end product) Type and quality of the raw material

Table 3 - Minimum requirements for wastewater disposal in water

Type	Matter which can be removed by settling3)	BOD51)	COD2) 4)
Slaughterhouses and meat-processing plants ADPs	< 0.3 ml/l < 0.5 ml/l	< 35 ml/l < 40 ml/l	< 160 ml/l < 30 ml/l

Key:

1) BOD5 = Biochemical oxygen demand over a 5-day period, with oxygen consumption determined in this period (g O2/l wastewater at T = 20°C)

2) COD = Chemical oxygen demand in the reaction with KMnO4 or K2Cr2O7 as the oxidation agent (mg O2/l wastewater)

3) Random sample

4) 2hr mixed sample

Slaughter costs are increased because of increased investment costs and running costs for wastewater treatment in relatively expensive treatment plants. Consequently animals may be slaughtered outside instead of inside slaughterhouses and thus no comprehensive check on hygiene conditions can be guaranteed.

After eliminating solids by mechanical purification, pond systems or the seepage of wastewater into the ground can be considered a substitute for biological treatment systems, provided that this does not pollute the groundwater mains or groundwater collection installations used for the drinking water supply.

The following can help slaughterhouses and meat-product factories reduce their wastewater pollution and dispose of their effluent correctly:

- better understanding of environmental issues by personnel;
- installation of technical facilities for improved separation of blood from the wastewater system;
- removal of waste of coarser consistency from production area floors before wet cleaning;
- fitting of sludge buckets in floor drains;
- fitting of wastewater screens to separate solids from the wastewater (these solids have a high protein content and can be passed on to ADPs);
- installation of sludge trap and fat separator;
- flotation plants (mechanical flotation treatment);
- supplementary biological clarification as a second treatment stage following mechanical treatment in plants which discharge their wastewater directly into surface water.

Wastewater from ADPs has to be sterilised.

2.2 Air pollution

Emissions occur primarily in the form of air discharged from the following areas:

Table 4 - Emissions from outgoing air

Type	Source area
Slaughterhouses Meat-product factories ADPs	Stalling, possibly also storage, confiscated meat Processing, smoke (cooking plant) Delivery, processing

To reduce the smell nuisance, slaughterhouses in Germany must, wherever possible, be sited at a distance of at least approx. 350 m from the nearest residential building.

Odours arise due to the odour of the animals themselves and changes to organic materials. As all smells arising in slaughterhouses are biodegradable, bio-scrubbers and biofilters can be used to reduce smells, as can adsorption and absorption processes.

Table 5 - Immission values (IVs) (TA-Luft [Technical Instructions on Air Quality Control])

Pollutant	IV 1 continuous operation	IV 2
Airborne dust (regardless of dust content) Lead and inorganic lead compounds as components of airborne dust -expressed as Pb -Cadmium and inorganic cadmium compounds as components of airborne dust -expressed as Cd -Chlorine Hydrogen chloride - expressed as Cl -Carbon monoxide Sulphur dioxide Nitrogen dioxide	0.15 2.0 0.04 10.0 0.10 10 0.14 0.08	0.30 mg/m3 - µg/m3 - µg/m3 0.30 mg/m3 0.20 mg/m3 30.00 mg/m3 0.40 mg/m3 0.20 mg/m3

Waste gas from meat-product factories can be treated in a number of ways, including:

- post-combustion;
- condensation;
- absorption - adsorption;
- electrical separators for particulate substances in conjunction with the above processes.

The emission reference value is the total carbon in the organic compounds.

In new continuously operating plants, emission values can be contained with technical installations so that:

- the established immission values (see Table 5) are not exceeded, and
- as experience has shown, no odour nuisance occurs where the chimney is of the correct height for gas disposal.

The installation of ventilation and air-extraction systems, waste gas systems etc. incurs high investment costs and this in turn can lead to high slaughterhouse fees which users cannot afford.

The following values are recommended to reduce substances which cause odours in ADPs:

- thermal post-combustion: 20 mg/m3 carbon in the combustible substances.
- other post-treatment systems:

The total frequency of odour assessments of emitted spent air, measured by the olfactometry process with 50% negative evaluations (ADP odour not perceivable) must produce a dilution factor of 100. A solids emission value of 75 mg/m3 can be observed in the air emitted from meal, conveyor and storage systems. The air emitted from heating and air purification systems must be removed through a chimney of an appropriate height.

Odour emissions can be generally reduced or prevented by:

- designing enclosed working and production areas with windows which cannot be opened;
- closed process circuits;
- fitting of air locks;
- preventing any accumulation of materials which could result in the development of odours;
- spent air systems with appropriate air treatment, as shown in Table 6.

Table 6 - Reduction of odour emission due to spent air treatment

Type	System
Slaughterhouses Meat-product factories (Smoking installations) ADPs	Biofilters, waste gas scrubbing, active carbons Post-combustion, condensation, absorption, adsorption Wet scrubbing (multi-stage), heat treatment, biological treatment, earth filters, biological scrubbers

2.3 Noise

Potential sources of noise in slaughterhouses and/or meat-product factories and ADPs are:

Table 7 - Sources of noise

Source	Slaughterhouses	Meat-product factories	ADPs
Animal delivery Animal slaughter area Machine and process area Spent air system recooling chamber	X X X X	X X	X X