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Causes of water pollution
The specific contaminants leading to pollution in water include a wide spectrum of chemicals, pathogens, and physical or sensory changes such as elevated temperature anddiscoloration. While many of the chemicals and substances that are regulated may be naturally occurring (calcium, sodium, iron, manganese, etc.) the concentration is often the key in determining whatis a natural component of water, and what is a contaminant. 
Pathogens
A manhole cover unable to contain a sanitary sewer overflow.Coliform bacteria are a commonly used bacterial indicator of waterpollution, although not an actual cause of disease. Other microorganisms sometimes found in surface waters which have caused human health problems include:
Burkholderia pseudomallei
Cryptosporidiumparvum
Giardia lamblia
Salmonella
Novovirus and other viruses
Parasitic worms (helminths).
High levels of pathogens may result from inadequately treated sewage discharges.This can be caused by asewage plant designed with less than secondary treatment (more typical in less-developed countries). 
Chemical and other contaminants
Muddy river polluted by sediment. Photo courtesy of United StatesGeological Survey.Contaminants may include organic and inorganic substances.
Organic water pollutants include:
Detergents
Disinfection by-products found in chemically disinfected drinking water,such as chloroform
Food processing waste, which can include oxygen-demanding substances, fats and grease
Insecticides and herbicides, a huge range of organohalides and other chemical compoundsPetroleum hydrocarbons, including fuels (gasoline, diesel fuel, jet fuels, and fuel oil) and lubricants (motor oil), and fuel combustion byproducts, from stormwater runoff
Tree and bush debris fromlogging operations
TYPES OF WATER FROM A FUNCTION OF ITS POLLUTION
Urban waste water, sewage, water scrubbing, cooking water. The main pollutants of these are organic matter and microorganisms. These...