Definition - What does Sewage mean?
Sewage is waste material that is carried through a sewer from a residence or an industrial workplace to be dumped or converted to a non-toxic form. Sewage is more than 99% water, but the remaining material contains solid material, ions and harmful bacteria. This matter must be extracted from the water with a filtration process before the sewage can be released back into a natural water source.
Safeopedia explains Sewage
Large solid matter (more than 2cm in diameter) in the sewage is removed by a screening process and disposed of in a landfill. The water is then left to settle, and remaining solids sink to the bottom while oils and greases float to the top. These are scraped from the bottom and sprayed from the surface with water. The waste material is chemically treated with bacteria, which convert it into bio-gas that is in turn used to power the sewage plant. The water is also treated with bacteria then UV light to destroy harmful bacteria before it is released into the sea. Sewage is a major cause of disease in a community and it's effective management, therefore is important for health and safety.