1) River pollution can affect people, wildlife and the environment.
2) Loss of oxygen: River creatures and river plants need oxygen to survive. When raw (i.e. untreated) sewage enters a river system it is broken down by bacteria in the water to create ammonia. However, this process uses up a great deal of oxygen. A lack of oxygen can destroy river wildlife.
3) Eutrophication: This is the term for an increase in nitrate levels in a river, which can rise due to pollution. Too many nitrates (often from agricultural products) encourage plant growth, particularly algae. Algae uses up oxygen and blocks out light. This affects the amount of wildlife in the river and turns the water green.
4) Human health: Can be damaged by high nitrate levels in a river. In recent years high nitrate levels have been detected in drinking water in the UK and other parts of Europe. Reducing nitrate levels requires expensive water treatment processes.