Water is very important for life and plays a crucial role in maintaining the earth’s ecosystems. However man’s developmental activity has increasingly polluted water sources, making clean and drinking water, difficult to find. Water pollutants can be attributed to various sources like pesticides, sewage, nutrients and synthetic organics etc. which introduce various pollutants and toxicants. Water pollution can impact all living creatures and can lower the quality of water, rendering it unfit for drinking. Therefore nations all around the world have taken steps to ensure that the water consumed by its population, is clean and harmless. Nations, states and regional governing bodies have exclusive water quality monitoring institutions, which ensure that the drinking water available within its allocated jurisdiction is safe. In the US, these are the national drinking water standards formulated by the Environmental Protection Agency (EPA). These standards are specific to each polluting material and its quality standard is defined, such that the permitted quantity is harmless to humans.
The quality standards of water are determined by evaluating three aspects namely biological, physical and chemical. Every institution monitoring water quality has a set of standards defined for each of these three attributes. The quality of a given water is established based on these set of standards. A biological assessment of water can indicate water quality when species that are sensitive to pollution are observed in a given water body, which is also an indication of a good quality water (Wheeling Jesuit University, 2004). Also the quality of organisms in the water needs to be considered. When there is a lesser number and fewer types of organisms, then the quality of water is lower. Water is also subjected to chemical assessment to study its pollutants. The chemical parameters like pH, hardness, alkalinity etc., are a reflection of the presence of pollutants, when the measurements are beyond the permissible range. Chemical tests may also directly reveal the presence of chemical pollutants like nitrogen, phosphorus, sulfur dioxide, nitrogen oxide etc. Some pollutants like mercury do not breakdown, thereby pose long term health risks (Rogers, 2010). Physical parameters are also important indicators of water quality, which can also indicate certain forms of pollution. For instance water temperature changes are indicators of certain effluents.
It is important to distinguish between water quality criteria pollutants and the maximum contaminant level (MCL). Pollutants are the attributes that cause the deterioration of water quality, while the permissible level is the MCL. Certain attributes of water may be described as primary parameters while others may be described as secondary parameters. The primary parameters include organic and inorganic chemicals, radioactive elements and microbial pathogens (EPA, 2012). The secondary parameters include chloride, color, odor, pH, dissolved salts, foaming agents etc. which affect water quality.
These parameters therefore give rise to primary and secondary drinking water standards respectively. The MCL and the Secondary Maximum Contaminant Level (SMCL) establishes the upper permissible limits for these contaminating attributes. When these pollutants are within their respective specified limits, then there is no known or expected health risk. Based on these standards, regional, state and federal agencies monitor water quality by testing and treating them.
Therefore the water quality standards have a limiting level specified for every pollutant, presence beyond which the water is rendered unfit. Thus a MCL is associated for major microorganisms, disinfection byproducts, organic and inorganic chemicals, disinfectants and radio nuclides. For instance EPA limits for metals include Antimony of 0.006 (mg/L)2 , Cadmium of about 0.0005 (mg/L)2 while it is zero for lead. With regard to radio-nuclides there is zero tolerance for alpha and beta particles, uranium and radium.
Wheeling Jesuit University (2004) Water quality assessment: Overview . Retrieved from http://www.cotf.edu/ETE/modules/waterq3/WQassess1.html
Rogers CD (2010) What kind of chemical pollutants pollute water? Retrieved from http://www.livestrong.com/article/159981-what-kind-of-chemical-pollutants-pollute-water/
(EPA, 2012) National Recommended Water Quality Criteria. Retrieved from http://water.epa.gov/scitech/swguidance/standards/criteria/current/index.cfm