Sewage is a liquid waste released by homes, industries, hospitals, offices and other users which also includes rainwater that has run down the street during a storm or heavy rain.
Sewage water contains harmful substances with it which washes off roads and rooftops. It is a complex mixture containing suspended solids, organic and inorganic impurities, nutrients, saprotrophic and disease causing bacteria and other microbes. So, when sewage discharge untreated into rivers or seas, it will be dangerous for aquatic plants and animals.
