A Tour of Beckton Sewage Works A Tour of the Beckton Sewage treatment Plant Sewage treatment is an important part of the maintainence of a healthy river. When this is diluted fourfold or more in a river, the BOD is reduced to two or three, which is sufficiently low for most river life. Sewage contains a mixture of substances.
Most domestic sewage is very easy to treat using the methods seen here.
If the sewage is contaminated by toxic metals or organics, then it can severely disrupt the cleaning process. The Northern Outfall Sewer serves much of London north of the Thames. It is probably the biggest such inflow in the country. The flow here is controlled to maintain most particles in suspension. However, the larger particles settle here as grit, and are cleared from time to time.