How are Water Quality Standards Determined

According to the United Nations, the declining water quality has become a global issue, which affects human health in a significant manner. Among the factors which contribute to a decline in the water quality include the population growth, expansion of  industrial and agricultural activities as well as climate change. However, in order to maintain the quality of water reserves, The Federal Government’s Environmental Protection Agency (EPA) has formulated the national standards for drinking water, which require all municipal water supplies to be measured against these standards.

The practicality of assessing water quality

In determining the water quality, three classes of attributes should be considered and these include the biological, chemical and physical attributes. However, due to the enormity of assessing all the water bodies in a country, especially in the case of United States where there are more than 3,600,000 miles of river and streams alone, only recognized water bodies used for certain purposes such as drinking, recreation and industries, could be assessed. The rest of the water bodies will remain to be assessed as and when it is required.

The primary and secondary drinking water standards

According to the EPA, there are attributes which need to be checked as having a primary importance over drinking water quality and attributes that are of secondary importance. Among the attributes that are of  primary importance, organic and inorganic chemicals, microbial pathogens and radioactive elements will be assessed using the Maximum Contamination Level. The secondary drinking water standards on the other hand will regulate the chloride, color, copper, corrosivity, foaming agents, iron, manganese, odor, pH, sulfates, total dissolved solids, and zinc levels in the drinking water against the measurement of Secondary Maximum Contaminant Level.

Biological assessment of water quality

When assessing for water quality, biological assessment refers to the assessment of the number and type of organisms inhabiting the waterways. When the water quality is poor, the number and types of organisms living in the water way will be less. At the same time, the presence of highly sensitive organisms to pollution in waterways indicates a higher quality of the water.

Chemical assessment of water quality

During chemical assessment, scientists will be looking for attributes which may cause the water to be aesthetically poorer in quality or even toxic to human consumption. Such assessments will look for elements and molecules which are dissolved or suspended in the water and among the commonly assessed attributes, the pH, alkalinit, hardness, nitrates, ammonia, phosphates, dissolved oxygen, presence of fecal coliform…etc are considered rather important.

Physical assessment of water quality

The path taken by a stream of water, the presence of bends, cold-water pools, riffles…etc will contribute towards the ability of a waterway to flood the surrounding area and provide a habitat for certain aquatic plants and animals. Thus, such characteristics can also be used to assess the water quality and therefore its suitability for human consumption.


Although it is difficult to assess all the water bodies in a country, it is possible to make use of the quality standards to assess and compare between the important water sources used at least for human consumption.