What are the causes of water pollution and suggest measures for control of water pollution?

Water pollution and its control:
Ganga Action Plan: Government of India launched this plan in 1985. Recently it is renamed as national river conservation project/plan. 

The Major Water Pollutants:

• Domestic Sewage: Sewage is the major source of water pollution in cities and towns. Sewage has to be passed through treatment plants.
  Biological Oxygen Demand: BOD indicates pollution load in the sewage.
  Algal Blooms: Presence of large amounts of nutrients in water causes excessive growth in algae called algal blooms.
• Industrial Effluents: Untreated industrial effluents released into water bodies pollute rivers and streams BOD and COD rise due to organic and inorganic pollutants in water.
  Biomagnification: Increase in the concentration of the pollutant like DDT at successive trophic levels in aquatic food chain is biomagnification.
  Eutrophication: Due to pollutants like nitrates and phosphates in lakes algae and plants grow.
  Consequently, animal life proliferates. Due to deposition of organic matter slowly the lake disappears.
• Thermal Pollution: Hot water flowing out of industries causes thermal pollution in water bodies.

Measures to control water pollution:

• Ecological Sanitation: Using ecosan toilets can reduce water pollution. In ecosan toilets water is not used and human excreta is converted into chemical fertilizer.
• Used hot water from factories should be released directly into the natural water bodies. It should be cooled first before release.
• Industrial effluents, domestic sewage must be treated and recycled.