Hesperian Health Guides
The Problem of Sewage
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Sewage systems use water to carry waste away in pipes. They can improve community health, especially in crowded urban areas. But to prevent health problems, sewage must be treated to make the water safe to return into waterways and for reuse.
Sewage treatment is costly, and more often than not, sewage is dumped without being treated. This spreads waste and all the germs, worms, and toxic chemicals it may contain, causing health problems such as hepatitis, cholera, and typhoid in places where sewage is dumped.
Even with costly sewage treatment, using water to carry away waste is often not sustainable and can lead to problems such as:
- contamination of drinking water sources downstream.
- contamination of land where people live and farm.
- loss of nutrient resources (fertilizer) for farming.
- contamination of water sources used for drinking, bathing, and farming.
- bad smells.
Sewage systems also cause health problems when different kinds of waste are mixed together, such as when factories dump toxic chemicals into sewers. This contamination makes the treatment and safe reuse of wastewater very difficult.
|The people most affected by untreated sewage |
are those who live where it is dumped.
The safest low cost way to manage sewage is to treat it close to where it is produced, and then to allow the water to absorb into the soil and nourish plants. The most common way to do this is to use a septic tank (a large container underground where solids collect and decompose) and a leach field (where liquid flows out and into the soil). This method, however, requires technical planning beyond the scope of this guide. (For more information, see Other Water and Sanitation Resources.)
Sewage systems use a lot of water to do a job that can often be done with very little or no water. Communities with little water, or that cannot afford a sewage system, will benefit from other types of toilets.
People build their own sewers
Orangi Township is a settlement of 900,000 people in Karachi, Pakistan. For many years, Orangi had no safe water or sanitation services. Sewage and wastewater ran in open ditches, breeding flies and mosquitoes, and causing illness. In 1980, Dr. Akhtar Hameed Khan began the Orangi Pilot Project, or OPP, to help people identify their health problems and come up with solutions.
Orangi residents decided an underground sewage system would most improve their lives. At first they expected the government to build it, but Dr. Khan knew that the Karachi government would not give them money to build a sewage system. After much discussion, the people of Orangi decided that even though they had no money, they could build the sewers themselves.
The first step was to develop community organizations. Each lane consisting of 20 to 30 houses was organized to build a sewer and applied to the OPP for assistance. The OPP surveyed the lane and prepared plans. The lane organization then collected money from the people to build their sewer.
At first, many people did not know how to mix concrete or to dig sewer pits that were flat and level, so some of the work was not done well. After 2 years, many faulty sewers had been built and others were still not built. The OPP organizers realized they had not trained people well enough, so more training sessions were held. This time, women and children were included. The work improved, and design changes were made to better serve the community, reduce costs, and finish the system more quickly.
After a few years, every lane had sewers to take waste away from people's homes. Health conditions improved and Orangi became a more pleasant place to live. But there was still a problem. The people of Orangi could build sewers, but they needed government support and money to build a sewage treatment plant. The government would not give the money. Many years later, the government found and funded a lower cost solution. They connected the sewers to a filter system that cleaned the sewage as it moved downstream. By working together to build their own sewers, the community took an important first step. The OPP helped the government and many experts to see that community health could be greatly improved by building a local sewage system to fit both the needs and the abilities of the community.