pollution in water

The specific contaminants leading to pollution in water include a wide spectrum of chemicals, pathogens, and physical changes such as elevated temperature and discoloration. While many of the chemicals and substances that are regulated may be naturally occurring (calcium, sodium, iron, manganese, etc.) the concentration usually determines what is a natural component of water and what is a contaminant. High concentrations of naturally occurring substances can have negative impacts on aquatic flora and fauna.

Oxygen-depleting substances may be natural materials such as plant matter (e.g. leaves and grass) as well as man-made chemicals. Other natural and anthropogenic substances may cause turbidity (cloudiness) which blocks light and disrupts plant growth, and clogs the gills of some fish species.

Alteration of water's physical chemistry includes acidity (change in pH), electrical conductivity, temperature, and eutrophication. Eutrophication is an increase in the concentration of chemical nutrients in an ecosystem to an extent that increases the primary productivity of the ecosystem. Depending on the degree of eutrophication, subsequent negative environmental effects such as anoxia (oxygen depletion) and severe reductions in water quality may occur, affecting fish and other animal populations
Disease-causing microorganisms are referred to as pathogens. Pathogens can produce waterborne diseases in either human or animal hosts.Coliform bacteria, which are not an actual cause of disease, are commonly used as a bacterial indicator of water pollution. Other microorganisms sometimes found in contaminated surface waters that have caused human health problems include:

Burkholderia pseudomallei
Cryptosporidium parvum
Giardia lamblia
Salmonella
Norovirus and other viruses
Parasitic worms including the Schistosoma type
High levels of pathogens may result from on-site sanitation systems (septic tanks, pit latrines) or inadequately treated sewage discharges. Older cities with ageing infrastructure may have leaky sewage collection systems (pipes, pumps, valves), which can cause sanitary sewer overflows. Some cities also have combined sewers, which may discharge untreated sewage during rain storms.Silt (sediment) from sewage discharges also pollutes water bodies.


Muddy river polluted by sediment.
Pathogen discharges may also be caused by poorly managed livestock operations
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 compounds
Petroleum hydrocarbons, including fuels (gasoline, diesel fuel, jet fuels, and fuel oil) and lubricants (motor oil), and fuel combustion byproducts, from storm water runoff
Volatile organic compounds, such as industrial solvents, from improper storage.
Chlorinated solvents, which are dense non-aqueous phase liquids, may fall to the bottom of reservoirs, since they don't mix well with water and are denser.
Polychlorinated biphenyl (PCBs)
Trichloroethylene
Perchlorate
Various chemical compounds found in personal hygiene and cosmetic products
Drug pollution involving pharmaceutical drugs and their metabolites, this can include antidepressant drugs or hormonal medicines such as contraceptive pills. These molecules can be small and difficult for treatment plants to remove without expensive upgrades.
File:Pollution.ogv
Macroscopic Pollution in Parks Milwaukee, WI
Inorganic water pollutants include:

Acidity caused by industrial discharges (especially sulfur dioxide from power plants)
Ammonia from food processing waste
Chemical waste as industrial by-products
Fertilizers containing nutrients--nitrates and phosphates—which are found in storm water runoff from agriculture, as well as commercial and residential use (see nutrient pollution)
Heavy metals from motor vehicles (via urban storm water runoff) and acid mine drainage
Secretion of creosote preservative into the aquatic ecosystem
Silt (sediment) in runoff from construction sites, logging, slash and burn practices or land clearing sites.
Macroscopic pollution – large visible items polluting the water – may be termed "floatables" in an urban storm water context, or marine debris when found on the open seas, and can include such items as:

Trash or garbage (e.g. paper, plastic, or food waste) discarded by people on the ground, along with accidental or intentional dumping of rubbish, that are washed by rainfall into storm drains and eventually discharged into surface waters.
Nurdles, small ubiquitous waterborne plastic pellets. See plastic pollution and microplastic pollution.