What is water pollution causes and effects?
“The adverse change in composition or condition of the water such that it becomes unsuitable for the purposes, for which it would be suitable in its natural state.”
Point sources: E.g., sewage outlet of a municipal area or effluent outlet of a factory.
Non-point sources: E.g., City storm water flow, agriculture runoff.
Types of Pollutants :
- House hold detergents
- Domestic sewage
- Industrial wastes
- Offshore oil drilling
- Thermal power plants
- Pollution of detergents in water prevents the decomposition of organic compounds as it forms a thin film around them due to its low surface tension (surfactant nature). This results in accumulation of organic substances in water.
• Decreasing of dissolved O2 (DO) content of water bodies.
• Higher biological oxygen demand (BOD). BOD is the amount of O2 in mg required to decompose organic matter present in one litre of water kept at temperature 20°C for 5days. If it is 4000 mg/ litre, water is heavily polluted.
• COD (chemical oxygen demand). It indicates total O2 requirement of all the O2 consuming pollutant materials present in water. Its value is higher than BOD.
• Annelid worm Tubifex and some insect larvae act as indicator species for polluted waters.
• Persistent pesticides (e.g., DDT) pass into food chain and their increase in amount per unit weight of organism with the rise in trophic level is called biological magnification.
• Bio-magnification of DDT causes haemorrhage, softening of brain, liver cirrhosis, hypertension etc.
• Eutrophication is increase in amount of nutrients in water due to detergents, pesticides etc and it leads to organic loading, depletion of O2
• Minamata disease is due to presence of mercury in water.
• Itai-itai (ouch-ouch disease) is caused by Cd.
• Excess nitrate reacts with Rb and forms non functional methaemoglobin that inhibits O2 It is known as methaemoglobinemia or blue baby syndrome.
• Skeletal fluorosis is caused by excess amount of fluoride in drinking water.
• Black-foot disease is caused by chronic exposure of arsenic.
• Excess copper leads to hypertension, uremia, occasional fever and coma.