Effluent sewer
Effluent sewers also currently serve fewer people than septic systems, which also use septic tanks, but simply dispose of the effluent by draining it into a leach field. About one quarter of United States homes dispose of their wastewater with septic tanks. However, effluent sewers are being looked at as a sewage treatment solution in areas where gravity sewer systems are not well-suited or when the high capital cost to build a gravity system is prohibitive. Areas that are less than ideal for gravity systems include areas that are large, but extremely flat and areas that require long-distance pumping, such as where homes are widely spread out or when several small villages or towns connect their sewage systems so that a centralized plant can be built.
Water supply and sanitation in Kenya
The Citizen Report Card moreover indicates that septic tanks are often used for the disposal of wastewater from flush toilets in Mombasa. Pit latrine users from Nairobi, Kisumu and Mombasa indicated that some wastewater empties into storm sewers, soak-aways and cess pits designed for kitchen waste, thus causing environmental pollution. In 2001 a pollution incident occurred in the town of Embu. Raw sewage was discharged from sewage treatment works into a nearby river and caused the death of 28 people who used the water downstream for domestic purposes.