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<International Source Book On Environmentally Sound Technologies
for Wastewater and Stormwater Management>

4.1 On-site wastewater treatment systems

On-site treatment relies on decomposition of the organic wastes in human excreta by bacteria (Section 2 (2.3)). This can take place in a simple pit in the ground or in specially designed tanks to promote the bacterial decomposition of the wastes. Unless re-use of the wastewater is specifically intended (see Section 2 (6) on Wastewater reuse), the overflow from the pit or tank is allowed to soak into the ground. Further bacteriological decomposition and soil filtration, adsorption and purification processes take place in the soil. Potential of groundwater pollution, however, exists with on-site treatment and disposal systems, because not all pollutants (e.g nitrate) are removed by these processes.

Pit latrine, pour flush latrine, composting toilet, septic tank and two improved on-site treatment units are described below because they represent major types of on-site treatment systems. Variations of these exist and some are described in greater detail in the Regional Overviews for regions where these systems are used. The treatment principles are, however, covered under these major types.

 

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