Sewage.

Sewage is a big contributer to pollution. Sewage is mainly a liquid waste containing some solids produced by humans which typically consists of washing water, faeces, urine, laundry waste and other material which goes down drains and toilets from households and industry. Sewage services exist to manage sewage by collection, treatment and recycling or safe disposal into the enviornment. Sewage pipes, or sewers, collect sewage and take it for collection or disposal. Sewage dumped into a river can flow into the ocean and it kills tons of sea creatures every year. Sewage treatment is the process of removing the contaminants from sewage to produce liquid and solid suitable for discharge to the environment or for reuse.