Septic tank
In the United States, the 2007 American Housing Survey indicated that about 20 percent of all households rely on septic tanks, and that the overwhelming majority of systems are located in rural (50%) and suburban (47%) areas. Indianapolis is one example of a large city where many of the city's neighborhoods still rely on separate septic systems. In Europe, septic systems are generally limited to rural areas.
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.