What is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas?

Sewage is waste water released by homes, industries, hospitals, offices and other users. It also includes rainwater that has run down the street during a storm or heavy rain. The water that washes off roads and rooftops carry harmful substances with it. Sewage is a liquid waste which has dissolved and suspended impurities as contaminants or pollutants. If this untreated sewage is discharged into rivers or seas, it may cause water pollution and soil pollution in which both the surface water and groundwater get polluted. Groundwater is a source of water for wells, tube wells, springs and many rivers. Therefore, if it gets polluted, it becomes the most common route for water borne diseases. They include cholera, typhoid, polio, meningitis, hepatitis and dysentery.