|GATE - 1/95 - Waste Water: Resource Management and Environmental Hygiene (GTZ GATE, 1995, 56 p.)|
The decision to install a flush-sewer system in German towns and its consequences by Engelbert Schramm
The introduction of the water closet and a disposal system using water to flush faeces to rivers by passing through a technical network of sewers and a sewage treatment plant was a controversial issue in 19th century Germany. This method which was widely practised in Europe's industrial cities clearly did nothing but shift the wastewater disposal problem. Engelbert Schramm feels that this system has reached its economic and social limits in highly industrialised countries such as Germany.
Before industrialisation, when Germany's towns were still quite small, human excrements were collected in cesspits usually located under the latrine. When the cesspit was full it was emptied and people either spread the contents over their own fields outside the town, or this manure was collected by farmers.
Complaints that towns were becoming "mucked up" mostly related to the excrements of riding horses, cart horses and draft oxen which littered the streets. The disposal of human faeces, in contrast, functioned quite smoothly up until the 19th century. Problems only set in when industrialisation attracted more and more people to the towns, which began to spread over larger areas. The average distance to fields to be manured also increased.
The flush sewer system
The emptying of the cesspits, and the fact that domestic servants emptied the night-pails made it impossible for the rich citizens to preserve their own «private sphere». The aristocracy developed a sensitivity to the smell caused by transporting faecal matter and welcomed the news that a water closet had been invented. This toilet was emptied by a siphon outlet and had an air-trap drain to prevent any odours escaping.
With the water closet, a seemingly fascinating solution had been developed: the flushing sewerage system which used water to transport faecal matter into the rivers via artificial channels underneath the towns. In 1842 the first flushing sewerage system on the European continent was built in Hamburg. Other urban planners soon began to copy this example.
Most physicians, engineers and local politicians in Germany felt that this technology was the decisive step towards establishing a new system to transport faecal matter. Faeces were to be transported through the sewerage system, if possible within an hour, from the houses into the river. This rapid transport of faeces would - it was thought - have a positive impact on the health conditions in urban centres. It would relieve the contamination of the soil which hygienists thought to be the cause of numerous diseases.
Large quantities of water, unthinkable up to then, were flushed through the closets in the houses. A centralised water supply system and a quite irrational use of clean water were preconditions for transporting faecal matter. The flushing sewer system transported domestic wastewater, waste fluids from industrial production and, in Germany, also rain water from paved surfaces. 270 m³ of water per inhabitant were transported each year through the urban sewerage network. This enormous water throughput was necessary to channel the wastewater through the underground without stagnation.
The debate on the flush sewer system
Constructing centralised sewage systems and excessive water supply systems was an expensive affair for urban dwellers, and consequently, setting up a flush sewerage system to remove faeces was usually a very controversial is sue. Alternatives were developed, some of which even reached technical maturity:
· The Dutch engineer Liernur developed a vacuum toilet which sucked faecal matter into containers situated in the vicinity which were regularly emptied.
· Other towns operated so-called barrel systems. The containers were regularly emptied and the faecal matter which was not directly distributed to farmers in the region was processed to fertiliser in special factories.
In light of these options many local politicians, physicians and engineers no longer saw the need to build a sewerage system. Finally the specialists split into two factions. The German Association for Public Health Care (Deutscher Verein fentliche Gesundheitspflege) spoke in favour of building a sewerage system on 26.9.1877. Its members did not see any justification in prohibiting the discharge of sewage effluent bearing the faecal matter from closets into surface waters because "the scientific impact and cost of a tolerable degree of river pollution is not sufficiently clarified to permit generally valid regulations at the present time".
As reaction to this the International Association for the Conservation of Clean Rivers, Soil and Atmosphere (Internationaler Verein fur die Reinhaltung der Flusse, des Bodens und der Luft) was established just four days later. Its members demanded that the faecal matter should not be discharged into the sewerage network and subsequently into the river waters. They repeatedly called attention to the fact that the flush sewerage system transformed rivers into cloacas which prohibited swimming and made the water undrinkable. Opponents of the sewerage system put forward the British example to assess such impacts: in 1865 the Thames, loaded with the faecal matter from London, lost its ecological balance; the resulting "Great Stink" even made it impossible for the British Parliament to carry on working.
Such conditions in Germany where the rivers are far longer, would affect wide areas of land. Although they did not adopt the preventive arguments of the International Association, local authorities did take action that municipalities could not discharge faeces-containing effluent from the sewerage system completely untreated into the rivers. But the first sewerage works only separated off the solid matter from the water using mechanical screens and sedimentation basins. This sewage sludge was then distributed to farmers as manure. Nowadays, farmers are very sceptical about this fertiliser because of the heavy metals, organic chlorine compounds and tensides contained in wastewater. Only one third of the total volume of sewage sludge is presently used in agriculture, the remainder is burned and dumped.
L'introduction des toilettes au et, en m temps, du tout-'ut, syst dans lequel les matis fles sont transport dans un rau de canalisations et sont rejet dans les fleuves apravoir trait dans des stations d'ration, a fait l'objet de plus d'une controverse dans l'Allemagne du 19. sie. Il s'est av trrapidement que cette mode, aujourd'hui couramment pratiqudans les villes europnes, n'a fait que transposer les probls d'assainissement n autre niveau. De l'avis de l'auteur, ce syst se heurte es limites d'ordre nomique et social, m dans un pays hautement industrialis
En la Alemania del siglo XIX fue muy debatida la introducciel inodoro o water y del correspondiente sistema de alcantarillado hidrico en el que las heces eran transportadas por conductos artificiales a las plantas depuradoras y de alli a los rios. Pronto se hizo patente que este mdo - de uso generalizado en las ciudades europeas de hoy- solo trasladaba los problemas derivados de la eliminacie aguas residuales a otros puntos. El autor opina que incluso en Alemania, un pais altamente industrializado, el sistema amenaza con superar los limites de viabilidad econa y social.
Step by step retrofitting
In the second half of this century it became clear that sewerage plants which only treated the water in a settlement basin would have to add a further treatment stage. More and more urban dwellers (and also households in rural regions) connected to the sewerage system with the consequence that water pollution intensified further. Domestic households also began to use more chemicals, which changed the composition of domestic wastewater. Fish death in Germany's large rivers was an experience repeated almost every summer.
The second purification stage in Germany's sewerage works is
usually a biological purification system: In a reaction tank, to which aerobic
bacteria have generally been added, organic pollutants are coagulated into
sludge flocs by means of dioxygenising bacterial metabolism. The purification is
all the more intensive if the oxygen supply is raised by artificial aeration
(requiring a high energy input).
But even optimally operating sewerage plants with both primary and secondary purification stages are unable to adequately retain the nutrients in the water. The algae plague and seal deaths in the North Sea in 1988 resulted in European Union's demands for greater elimination of nitrogen and phosphorus compounds (initially for sewerage plants in larger cities) in order to protect the rivers and the sea. This third purification stage usually consists of a chemical process in which some anaerobic biological processes are integrated.
Cost intensive re-equipping of existing sewerage plants is essential. Many towns, individual citizens and also local authorities are resisting the costs this entails; resistance is chiefly directed at the demands of the European Union. Local politicians forget that we are really just paying for decisions made in the 1 9th century.
Task Analysis Sheet: Introducing Latrines
Is it really a sanitation technology?
As early as the end of the last century - when only few towns possessed a sewage treatment plant - it was al ready clear that flush sewerage technology did not lead to an improvement in the health situation: A cholera epidemic in 1892 in Hamburg originated from the fact that wastewater polluted with cholera pathagens had infiltrated into the water-works. The typhus epidermic in the Ruhr Valley region in the early 20th century had the same cause. However, 20 years following the conflict on whether or not to introduce the flush sewerage system no one drew attention to the fact that the sewerage system constantly polluted river water with pathogens. The roots of the problem were thought to be the fact that urban or private water works did not sufficiently purify river water before feeding it into the supply system. Slow sand filtration, chlorination and other end-of-pipe technologies were stipulated for river-side water publication.
Only now are policymakers beginning to realise that the flush sewerage system just means a changed distribution of pathogens in the environment. They are transported out of town into downstream waters. Sewerage from Germany's cities pollutes downstream lakes and rivers with pathogens to such an extent that bathing had to be prohibited (pursuant to EU legislation). Therefore Berlin is discussing the further extension its sewerage plants. Micro-filters in a fourth purification stage are to retain viruses and bacteria. Will this make the flush sewerage system an ecologically sound method at long last?
Learning from the past
In retrospect the arguments put forward by the International Association which had disappeared after such a few years, were the right ones. The successful strategy of the German Association for Public Health Care to promote the flush sewage system did not link the status of centralised sewage treatment to public health care aspects but rather to the scientific knowledge at that time. This approach makes its mark in the purses of city dwellers: In Germany today a family of four has to pay c. DM 140 per month for water and sewerage. The 1 9th century water in*astructure based exclusively on a centralised system is now confronting its economic and social limits! It is high time to change the paradigm: Perhaps decentralised water treatment systems, compost toilet systems etc. can be further developed to make them not only feasible for urban fringes.
The question put forward by the "International Association" is still pointing in the right direction: "What means have we to ensure that latrines are sufficiently cleaned and human waste is safely removed without endangering the rivers?" The vision of a sustainable city which does not live at the expense of its environment could probably become reality if we draw the consequences from the past.
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