Sewage is a water-carried waste, in solution or suspension, that is intended to be removed from a specific place. It consists mostly of grey or black water. It is characterized by rate of flow, physical condition, chemical and toxic constituents and its bacteriologic status. Types of sewage · Domestic/sanitary sewage: The wastewater from residences and institutions, carrying bodily wastes, washing water, food preparation wastes, laundry wastes, and other waste products of normal living. · Commercial wastes: Liquid-carried wastes from stores and service establishments serving the immediate community. · Surface run-off: is that portion of precipitation that runs rapidly over the ground surface to a defined channel. Types of pollutants Organic pollutants and nutrients : sewage is a complex mixture of chemicals, with distinctive chemical characteristics. These include high concentrations of ammonium, nitrate etc. Sewage also contains the nutrients