Sewage water systems is the most important system that needs to be in place otherwise it can cause contamination of water releasing deadly toxins that can be hazardous for the body. Sewage treatment is the process of eliminating contaminants from industrial or municipal wastewater, containing mainly sewage plus wastewater (grey or black water). Physical, chemical, and biological processes are used to remove contaminants and produce treated wastewater or treated effluent, which is safe enough for release into the environment. A by-product of sewage treatment is a semi-solid waste or slurry, called sewage sludge. The sludge must undergo further treatment before being suitable for disposal or application to land.