Case study 10.3 Tin Smelter Project in Thailand
Notes: This case study can be used by trainees to make mitigation
plans and discuss post-project monitoring.
Name of the project: Environmental impact assessment for tin
Type of environmental analysis: EIA.
Type of project: This is a metal-refining industry. The
manufacturing process essentially involves heating the ore and utilizing the
difference in melting point temperature (alloy formation involves slightly
different methods) for obtaining the separation of the various components
including the production of the tin metal of over 99.9 per cent purity from the
original ore concentrate of approximately 73-75 per cent purity.
This is the only tin-smelting and refining plant in Thailand. It
is capable of producing about 40,000 Mt/year of refined tin, which is 20 per
cent of current total world production. A number of by-products are also
produced, including tin-lead.
The industry produces three types of waste: namely liquid, solid,
and gas. Domestic wastewater, laboratory wastewater and plant surface run-off
are the main liquid wastes. Heavy metals such as Fe, Pb, Ta, Nb, Ti, Sn, Al, Zi,
and Cn are the main heavy metal pollutants. Solid waste management does not pose
any significant problem. Some amounts of toxic heavy metals, including Pb, As,
Sb, and Bi, are emitted to the atmosphere. Also the sulphur present mainly in
the fuel can generate significant quantities of SOx. Thus air
pollution is the most threatening hazard at a tin smelter.
The tin smelter is located at the southern promontory of Ao Kham
Bay on the southeast shore of Phuket Island, which is about 6 km south of Phuket
town though 12 km by road. The plant is located adjacent to the tin ore
processing facility. The plant is bounded on the east and south by the sea and
the west and southwest by coconut groves. The total area of the plant is 5.8
Reports on pertinent studies
See References 1-4, page 305.
Environmental study area
The study area includes the land mass within approximately a 5 km
radius of the plant. This area has been determined to cover more than adequately
any resources which may be significantly affected by the tin smelter operation.
The EIA team consists of two co-managers, with one project field
engineer, two air quality experts, one socio-economist, one water quality
expert, and one ecologist, with support staff.
EIA budget adequacy
Adequate budget was provided.
The methodology for preparing the EIA is that recommended by NEB
(Ref. 5, p. 305). It is based on the methodology developed by the Battelle
Institute/United States Army Corps of Engineers. In this methodology
environmental resources are classified and evaluated in four general headings,
namely: (a) natural physical resources, (b) natural ecological resources, (c)
human use of economic development resources, and (d) quality-of-life values. In
addition to estimating effects of the tin smelter operations on these resources,
and identifying, delineating, and quantifying adverse effects, the method
includes preparation of recommendations for minimizing unavoidable adverse
effects and for offsetting these by positive enhancement measures.
To supplement the data from different sources, a number of field
surveys were made covering all specialized environmental impacts (including
socio-economics, wildlife, flora, and fauna, plus a sampling analysis of
wastewaters, drinking water quality, health status of the workers, etc).
Existing environmental conditions
Based on discussions with long-time residents of Phuket, it
appears that prior to the construction of the tin smelter (about 20 years ago),
the study area was sparsely populated, with land use including some coconut
groves, rubber plantations, and secondary forest. Agricultural development
coupled with population growth has resulted in increases in cultivated crops as
well as coconut and rubber plantations and thus created a more densely populated
During the past 20 years (the duration of tin smelter operations),
several new families have moved into what was previously a sparsely inhabited
area. This can be expected as a result of increased economic opportunities from
the industrial development, improvements in transport/access, etc. It may also
be expected that the increased population may result in increased frequency and
opportunities for complaints. Complaints on record cover blasting noise and
Blasting noise from slag granulation: frequently 2-3 times/day,
mostly occurring during night; continuous blasting noises (> 100 times in
each duration); disturbs relaxation time of surrounding people, patients,
children, and babies; and caused different levels of vibration to houses
depending on distances - creating damage to items, e.g. mirrors, window panes,
and roof tiles.
Smoke from blasting and stacks: aesthetic nuisance (clothes and
houses got dirty, bad odours); and fear of illness due to bad odours.
Environmental base map
The environmental base map (EBM) shows the plant and its environs.
The EBM shows all potentially sensitive environmental resources, that is any
resource which might be significantly impaired by the plant operations,
including waste emissions.
Environmental effects from project
Adverse effects on physical resources
Air quality: odour and dust nuisance during certain hours on some
days (though the modelling and stack emissions indicate that the tin smelter may
not be the source); reduced yields from fruits from coconut plantations; and
visible damage to leaves.
Noise pollution: noise has affected most of the residents of the
Adverse effects on water resources
The wastewaters discharged from the laboratory and canteen without
any treatment are unsightly and these waters exceed Ministry of Industry (MOI)
standards for some parameters.
Adverse effects on human use values: agriculture
The smelter air emissions have caused significant reductions in
yields of coconut plantations. Also the toxic effects of groundwater and soil
polluted by tin dredge tailings which have been panned or stored in the coconut
groves by local villagers have caused the plants to yield less.
Adverse effects on quality-of-life values: socio-economics
About 90 per cent of the respondents at Ban Ao Makhan and 100 per
cent at Ban Laem Phan Wa Wee were negatively affected by noise and dust
Positive effects on human use values
Water supply: the tin smelter operations created beneficial
impacts on water supply in that the smelter made arrangements for local
villagers to utilize the groundwater supply developed by the tin smelter.
Mining/mineral resources: the operation of the tin smelter has an
obvious beneficial impact on local, regional, and national mineral resource
development and subsequent beneficial economic impacts.
Quality-of-life values: wage earning forms the major proportion of
household income in the area. The smelter has created job opportunities and
other related employment opportunities for the local villagers. These indicate
long-term benefits for the people in the area.
Land prices in the vicinity have increased because of the presence
of the industry. Economic benefits include benefits of increased earning and
creation of jobs for the workers and their families as well as the gross
regional product, and overall economic benefit to the nation.
Summarized projected effects
The impacts of the smelter operations are both beneficial and
adverse, with the beneficial impacts outweighing the adverse. The primary
beneficial impact is the economic benefit which is believed to play a major role
in the villagers' good primary healthcare. In addition, the provision of water
supply for many villagers is a primary beneficial impact.
The adverse impacts are related to air and noise pollution from
the plant. Apprehension naturally results regarding health when one believes
that air pollution is causing damage to vegetation, leaving deposits of dust at
the living quarters, and may be damaging to human health. These fears may or may
not be justified. The health data from the local clinic do not indicate any
difference in the health condition.
Measures for offsetting adverse effects
The cyclones, baghouses, and electrostatic precipitator are
generally performing well. Consideration should be given to undertaking the
corrective maintenance measures for the electrostatic precipitators (ESP)
recommended by Research Cottrell as these measures will ensure a longer and more
efficient operating life of the ESPs and should further reduce the frequency of
tripping of the ESPs; bag replacement and maintenance should be improved, and
the performance closely monitored; and consideration should be given to
upgrading the old ventilated baghouses, so that the emissions are from a stack
or stacks which can be monitored and also will reduce local dust deposition
during calm periods.
Stack emissions from liquidator 3 resulting from dross production
need additional pollution control in order to reduce the arsenic trioxide
emission concentration. It has been proposed that by cooling the gas prior to
baghouse filtration, the efficiency of filtration would increase. This cooling
could be accomplished by installation of a medium efficiency dry cyclone with
modification for air cooling in the exhaust line prior to the baghouse. It may
also be necessary to install a second baghouse in series or vent the baghouse to
an ESP. The approach here should be step-by-step to minimize unnecessary
expenditures. This means that air cooling on a pilot scale should be tested
first to determine the potential increase in arsenic removal efficiency of the
existing baghouse. Further steps would be dependent on the results of the pilot
testing. In addition it would be a good idea to only operate liquidator 3 on
windy days to increase dispersion.
A general "tightening-up'' and possibly some modifications are
needed for improving shop-floor ambient air quality. This is particularly true
for the electric furnaces during charging, the refining and casting area, the
hardhead tank, and the area around the AI/As dross storage room and liquidator 3
(particularly during liquidating). An analysis of needs for improvement in
hygiene lines, exhaust fans, protective structures, etc., is needed to enable
detailed design of cost-effective facilities. A corrosion control analysis
should be incorporated in the study in order to prevent further
corrosion-related gas line leakage.
The baghouse and hygiene system engineering study and improvement
planning is completed and detail design is underway. The construction was
expected to begin in the second half of 1986.
The water pollution analysis shows that the only pollutants
exceeding MOI effluent standards are from the laboratory and canteen. Because of
the small volume of wastewater and the vast dispersion/dilution effect of the
tides and currents, it is evident that the effluent does not significantly
impact on the local ecology. However, the smelter could easily meet MOI
standards by routing the canteen wastewater flow to a septic tank/oil trap
system and pumping the laboratory wastewater to the septic tanks system rather
than directly discharging to the sea. This will eliminate any direct discharge
of undiluted or diluted laboratory wastewater (this is the same disposal method
as is commonly used by laboratories in Bangkok).
The effect of noise pollution has been evaluated by noise level
measurements at various locations in-plant and in surrounding communities. Noise
pollution was shown not to be an occupational hazard for workers. The normal
plant operation does not have any significant effect on sound levels in nearby
villages. However, periodically, there are explosions due to slag granulation
which are reported to cause nuisance conditions at nearby residences. The
smelter has been and is continuously making every possible effort to reduce the
frequency of such explosions. The frequency has been reduced from the occurrence
of explosion in 18 per cent of tappings in 1983 to 14 per cent in 1985. This
results in an average of less than two explosions per week. It is possible that
this is the best achievable under present processing circumstances and is thus
an unavoidable impact. It is not feasible to shift processing times to ensure
that the slag explosions occur during the day. The smelter is continuing to
modify its processing to reduce the number of slag explosions. One of the
expansion plans is a new cooling water system, for the improvement of the water
pressure and water flow rate of the slag granulation system. The high pressure
and the high flow rate of granulating water will reduce the chance of slag
explosion and therefore reduce the frequency of slag explosion. The installation
of the cooling water system is planned within 1986/87 smelter budgets.
Solid waste pollution control is not a significant factor in the
assessment of environmental impacts of the tin smelter because the process solid
wastes are either recycled or sold as slag or dust.
The monitoring activities are planned to provide confidence in the
continuous improvements in pollution control at the smelter and to ensure that
the objectives of environmental protection are met.
The plan includes monitoring of both the natural environment and
public and occupational health-related parameters. The monitoring will include
systematic measurement of air and wastewater discharges from the smelter as well
as special periodic ambient environmental quality measurements.
The implementation of the monitoring plan will serve to provide
(a) establish a database to confirm meeting applicable MOI and
National Environment Board criteria and standards;
(b) ensure worker health and safety;
(c) assist in the efficient operation of the smelter by providing
feedback on operation/maintenance.
The monitoring programme includes point-source sampling for all
significant air and wastewater discharges and ambient air quality sampling for
the shopfloor and at the two nearby villages. The monitoring programme also
includes continued monitoring of drinking water quality, recording of
operational problems of air pollution control facilities, recording of blast
occurrences, and continuing safety/health checks. The smelter monitoring
programme will commence when appropriate equipment has been identified and
obtained. Periodic reports will be issued to the MOI as required.
From the overall assessment it can be concluded that, while the
tin smelter operations do cause minor effects on the local environment as a
result of wastewater and noise, the only significant adverse effects may be
caused by air emissions. These problems can be readily overcome so that the
overall adverse impacts of the smelter will be minor or possibly insignificant,
especially when compared to the major social and economic benefits derived
during the past 20 years of operation and which are expected to continue in the
future. These benefits are enjoyed by the local population, the Upper South
Region, and the nation.
1 Metal Levels Associated with Tin Dredging and Smelting and their
Effects upon Intertidal Reef Flats at Ko Phuket, Thailand, Coral Reef, Chapter
1, pp. 131-137, 1982.
2 Environmental Guidelines for Coastal Zone Management in
Thailand/Zone of Phuket, H. F. Ludwig/SEATEC, 1976.
3 Inception Report: Environmental Impact Assessment for Thailand
Tin Smelter, prepared by SEATEC Consortium, October 1984.
4 First Progress Report, Environmental Impact Assessment for
Thailand Tin Smelter, prepared by SEATEC Consortium, March 1985.
5 Manual of NEB Guidelines for Preparation of Environmental Impact
Evaluations, National Environmental Board,