Biology: Industrial Waste, Runoff & Sewage Pollute Rivers

Water pollution occurs when harmful substances enter a river from sources such as a factory pipe, a farm field, or a household drain, altering the water's chemistry and biology. Each source introduces a distinct pollutant: industrial waste carrying manufacturing chemicals, agricultural runoff where rainwater washes fertilizers off fields, and sewage from toilets, sinks, and washing. These pollutants matter because rivers support entire ecosystems and often supply drinking water. Their effects differ but connect through one theme: disrupting the balance of life in the water. Industrial chemicals poison fish and other animals directly. Fertilizers add excess nutrients, triggering algal blooms that strip oxygen from the water. Sewage introduces harmful germs while also consuming oxygen that fish need to survive. Understanding these sources and mechanisms shows how human activity upstream shapes water quality downstream, linking chemistry, biology, and everyday land use.