Water Pollutant - Phosphate
Phosphates are nutrients essential for plant as well as animal growth. But, when their concentration exceeds certain limit they pose serious problems to water bodies, and adversely affect water quality. Major sources of phosphates are non-point sources that include agricultural run-off and sewage or domestic effluent (West Cumbria Rivers Trust, 2015). Phosphate fertilizers used in agriculture are washed off during rains, and they reach nearby water bodies. Sewage receives phosphates from detergents and food or drink additives (West Cumbria Rivers Trust, 2015). Excess phosphates in the water body lead to algal bloom or “eutrophication” that completely destroys the quality of the water body, and prevents it from supporting other aquatic life forms (Oram, 2014).
Under normal conditions a water body has sufficient dissolved oxygen to support various planktons, fishes and other organisms, and there is a balance in the ecosystem. Once excess phosphates enter the water body, there is sudden increase in rate of algal and phytoplankton growth (Oram, 2014). Soon sun light penetration is also cut-off by surface algal layer, and the death rate of the plants and algae begins to rise. Bacteria consume remaining oxygen and metabolize the organic matter from dead organisms, releasing more phosphates into the water body (Oram, 2014). Thus, the pond or lake becomes anoxic, and microbial anaerobic metabolism releases methane as well as hydrogen sulphide gases, which are typical indicators of a decaying system. Certain algae such as blue-green algae may also release toxic substances, which are harmful to humans as well as animals (Oram, 2014).
Phosphate nutrient pollution in water bodies can be minimized by using household products with minimal phosphate content, preventing excess use of fertilizers in farmlands or gardens, preventing untreated sewage mixing with fresh water (West Cumbria Rivers Trust, 2015). Adopting nutrient removal and effluent treatment systems for large farms as well as large-scale animal feed preparation areas situated near water bodies can also minimize nutrient pollution (Oram, 2014). Unlike point sources of pollution for which a specific limiting concentration can be easily set, non-point phosphate sources cannot be regulated by simple cut-off limit values. Strict regulations and standards set based on quality of the receiving water body, as well as effluent discharge rate and concentration of the pollutant can help in minimizing phosphate nutrient pollution.
References
Oram, B. (2014). Phosphate in Water. Retrieved April 06, 2016, from http://www.water
research.net/index.php/phosphate-in-water
West Cumbria River Trust. (2015). Phosphates and Nitrates. Retrieved April 6, 2016, from
http://westcumbriariverstrust.org/assets/content/projects/file/Phosphates and Nitrates-20140609152524.pdf
