The vital water pollution sources are domestic wastes, industrial effluents and agricultural wastes. The other sources are oil spills , marine dumping, radioactive waste, global warming and eutrophication. Among all these sources , domestic waste (domestic sewage) and industrial waste are the most vital contributors to water pollution.
Domestic Sewage: Domestic sewage is wastewater created from the activities of household . It has organic and inorganic materials like phosphates and nitrates. Usually people dispose the household wastes in the nearby source of water , which eventually causes water pollution. The amount of organic wastes that can be degraded by the bodies of water is calculated in terms of Biological Oxygen Demand (BOD). BOD is the oxygen amount required by microorganisms to decompose the organic waste available in the sewage. An increase in the amount of BOD indicates that the water is more polluted with organic waste . Phosphates often cause algal bloom and eutrophication, which is most familiar in stagnant bodies of water such as ponds and lakes. Algal bloom and eutrophication lead to fish suffocation and other organisms in a water body.
Industrial Effluents: Wastewater from the manufacturing and processing industries also lead to water pollution. The industrial effluents consists of organic pollutants and also toxic chemicals. Some of the industrial source pollutants are lead, mercury, asbestos, nitrates, phosphates, and oils . Wastewater from food and chemical processing industries leads more to water pollution than any other industry . Also dye industries create wastewater which changes the quality of water especially water color. Since the water color is no longer the same , there is alteration in the penetration of light and hence it harms the aquatic plants and animals.
Agricultural Waste: Agricultural waste consists of manure, slurries and runoffs. Many agricultural farms practice the usage of chemical fertilizers and pesticides. The runoffs from these agricultural fields will lead to water pollution to the nearby sources of water such as rivers, streams and lakes. The seepage of fertilizers and pesticides will lead to groundwater pollution, which is more known as leaching. Although the agricultural waste quantity is very low in numbers , the effects are highly significant. Nutrient pollution increases the nitrates and phosphates in the water bodies, which causes eutrophication. [2]
