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.
Davyhulme Sewage Works
Conversion of the treatment process from chemical precipitation to septic tanks and sedimentation tanks began in December 1900, and was completed on 4 August 1904. The tanks covered an area of . Air was excluded from them by the formation of a scum on the surface, and anaerobic microbes broke down the sewage. The 'first contact bacteria beds' covered , with a similar area used for 'second contact bacteria beds'. There were also which were used for 'storm water filters'. The bacteria beds were filled with a media of coke or granite chippings, around which microbes formed a slimy film. The oxygen-loving microbes digested the organic matter in the sewage as it passed through the media.