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 Nigeria
Adequate sanitation is typically in the form of septic tanks, as there is no central sewerage system, except for Abuja and some areas of Lagos. A 2006 study estimated that only 1% of Lagos households were connected to sewers. Lagos has four wastewater treatment plants which have been rehabilitated around 2010. As of 2011, the state planned to build ten new "mega wastewater treatment plants" over the next five years with the help of private investors. These have not yet been completed.