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.
Abbey Mills Pumping Station
Lee Tunnel is a sewage tunnel that travels from Abbey Mills to Beckton Sewage Works and is designed to handle the 16 million tons of overflow sewage that was previously discharged into the River Lea each year. The tunnel boring machine's name, 'Busy Lizzie', was chosen via a competition open to local school children. Thames Water began construction in 2012 and on 28 January 2016, in a visit to the operations, London mayor Boris Johnson opened the tunnel for service.