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Pollutants Found in Sewage

The pollutants found in sewage include oxygen-demanding substances, pathogens, nutrients, and inorganic and synthetic organic chemicals, while thermal conditions can reduce the capacity of water to retain oxygen.

Since dissolved oxygen is necessary for aquatic life, anything, especially the many pollutants and wastewater which reduces the level of dissolved oxygen found in water, may cause disastrous effects to various ecosystems. This process is called the biochemical oxygen demand (BOD) and is also a measure of how effective the sewage treatment plant is operating through its various processes. Especially troubling for the sewage treatment plant is the industrial waste that comes from paper mills, food processing plants, tanning operation, and other manufacturing processes.

There is a multitude of pathogens which may be found in wastewater including those that cause gastroenteritis, leptospirosis, typhoid fever, salmonellosis, shigellosis, cholera, balantidiasis, cryp- tosporidiosis, amoebic dysentery, giardiasis, infectious hepatitis, etc. Individuals may come in contact with the pathogens either through drinking the water which is contaminated or swimming in contaminated water.

Carbon, nitrogen, and phosphorus are essential for living organisms and are the major nutrients found in natural water. Added to this is the large amount of these nutrients that may be found in sewage effluent, even that which has gone through conventional secondary treatment plants. In addition, there are large numbers of nutrients which come from fertilizing the soil. All of these can over-stimulate plants found in water, and cause serious problems with drinking water, making it toxic and also aesthetically unacceptable. Non-toxic algae blooms in reservoirs caused by septic leachate can contribute to taste and odor issues created in the reservoir. Uncontrolled algae can block out sunlight and cause serious problems to aquatic plants and animals by depleting dissolved oxygen in the water at night.

There are numerous inorganic and synthetic organic chemicals, especially from detergents, household cleaners, pharmaceuticals, synthetic organic pesticides, industrial chemicals, and manufacturing wastes, which cause severe problems in surface and groundwater supplies. Heavy metals can be very toxic to the various ecosystems.

Legal pharmaceuticals and personal care products are frequently deposited in toilets, as a supposedly safe way of disposing of them. In addition, discharge of bioactive metabolites of these drugs may also be found in the water, coming from urine and feces. Unfortunately, these drugs or metabolites may not be destroyed by the treatment process and therefore are found in bodies of water which may be used for drinking water purposes after treatment. Illicit drugs may also end up in the water supply.

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