Septic tank
A septic tank is an underground chamber made of concrete, fiberglass or plastic through which domestic wastewater (sewage) flows for basic treatment. Settling and anaerobic processes reduce solids and organics, but the treatment efficiency is only moderate (referred to as "primary treatment"). Septic tank systems are a type of simple onsite sewage facility (OSSF). They can be used in areas that are not connected to a sewerage system, such as rural areas. The treated liquid effluent is commonly disposed in a septic drain field which provides further treatment. However, groundwater pollution may occur and can be a problem.
Lee Tunnel
This long tunnel, of diameter , running from deep at Abbey Mills down to deep at its terminus at Jenkins Lane, East Ham, will capture , or 16 million tonnes, of sewage annually from the single largest polluting CSO in London. This sewage would otherwise flow straight into the River Lea, the Thames Tideway and eventually the Thames Estuary. However, the sewage is now pumped up to the Beckton Sewage Treatment Works – the largest sewage treatment works in Europe – and the resultant clean water emptied into the River Thames. The reason for starting at −75 m is to be ready to collect sewage from the lowest point of the Thames Tideway Tunnel, which is under construction and intended to connect.