Do sewage treatment plants use chemicals?
Wastewater originates from households, businesses, industry as well as storm drains and rainwater runoff. In general, wastewater contains approximately 99.9% water, with the remaining 0.1% representing dissolved solids or other suspended material. This material may include excreta, detergents from washing clothes and dishes, food residues, grease, oil, plastics, salt, sand, grit and heavy metals. Some wastewater from industrial or agricultural processes may also contain chemicals that may be harmful to the environment or public health and need to be neutralised or removed from the water before they can be safely reintroduced into the environment. The main objective of the wastewater treatment process is to purify the water and ensure that it is safe for subsequent use once it has been returned to the environment as part of the water cycle. Wastewater treatment involves several stages involving mechanical (physical), biological, chemical and membrane (filtration) based processes. ...