CHRIS KNAPTON / SCIENCE PHOTO LIBRARY CHRIS KNAPTON / SCIENCE PHOTO LIBRARY
Sewage works, aerial view. Sewage goes through several stages of treatment. Solid waste (sludge) is removed in settling tanks (round, lower left). Aeration tanks (rectangular, centre right) pump air into the sewage to encourage the growth of micro-organisms that feed on harmful bacteria. Further settlement and filtration in a variety of tanks (upper left, upper centre) removes the final sludge and microbes. In the gas tanks (top left), the decomposing sludge is used to produce methane to burn and generate electricity. This is Severn Trent's Burton Joyce works, Nottinghamshire, UK, one of the earliest (1952) power stations to use sewage. Upgraded in 2000. Photographed in 2004.
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