Describe how water quality is determined - Essay Example

Keywords: Water quality, guidelines, standards, contamination, pollutants, permissible limits, microbiological. Water Quality Standards Water is essential to life on this planet and its quality impacts both human beings and aquatic marine life (Anon., edugreen, n.d.). Pure water, fit for human consumption and other applications, is odorless, colorless and tasteless but these qualities are lost when contamination takes place. World Health Organization (WHO) has been the nodal agency for developing water quality parameters and recommending them for adoption by the different nations with appropriate modifications, through respective national agencies like the Environmental Protection Agency (EPA) of the US.

WHO guidelines are only recommendatory in nature, and factors like socio-economic conditions, traditional usage practices, need to conserve water as a resource etc. play important role in the quality standards of water in each country ((Fewtrell and Bartram, 2001). To study the quality and lay down relevant parameters, water is broadly divided under three different usages for developing standards for each category - drinking water, wastewater for reuse and recreational water (Fewtrell and Bartram, 2001. pp.17-20).

Contamination itself is caused by chemical, physical and microbiological factors. Hence quality standards are based on the matrix of water usage and the relevant contaminants. For example, permissible contamination in agricultural or recreational use water is significantly higher/different than that for human consumption. Thus, the pollutants and permissible limits for different water usages have been developed. Chemical contaminants are very many and include chlorine (as disinfectant), pesticides/herbicides (used in agriculture), toxic organic/inorganic chemicals from industry, soaps and other cleaning agents in domestic wastewater running into sewers, canals and river streams etc.

(Excel, n.d.). WHO guidelines indicate the tolerable daily intake (TDI) limits for presence of different chemicals in water, beyond which it is considered unfit for consumption. In respect of genotoxic carcinogens, TDI is nil. For other chemicals, standards of maximum permissible concentration levels are developed for each end-product. While developing the guidelines and standards, verification by relatively easy chemical analysis methods either on spot or in laboratories was kept in mind for practical reasons.

Physical contamination consists of suspended particles like sand, soil, clay, decaying vegetative matter, precipitated salts etc. apart from metals, dissolved salts and minerals. These contaminants give color, taste and odor to water, impacting quality of the end-products. Dissolved salts and minerals also discolor clothes when such water is used for washing. Multilayer filtration, water softening and demineralization processes help to reduce physical contamination of water. US-EPA recommends a limit of 500mg per liter or 500ppm for total dissolved salts (TDS) (Excel, n.d.).

Individual permissible limits have also been laid down by EPA for heavy metals (toxic) like arsenic, mercury, cadmium, lead and silver. Microbiological contamination is the presence of pathogenic microorganisms like viruses, bacteria, protozoa and helminthes, and is usually caused by fecal matter ingress. WHO guidelines identified Escherichia coli (E.coli) for sampling and recommend a zero presence in a 100 ml sample and a presence in