Water is used for many purposes and is generally considered to be a human right and a public resource. In order to maintain clean and safe sources of water for present and future use, national governments have developed and enforce water quality standards.
Water standards have been developed in order to protect beneficial uses of water bodies such as fishing, swimming, and drinking and to preserve healthy ecosystems. They are used to evaluate water monitoring data to assess water quality, to identify polluted or impaired water bodies that need to be protected, and they are also used to set limits on commercial discharges and to determine cleanup activities¹.
In order to protect water quality, most national governments as well as the World Health Organization have instituted guidelines and legal limits for drinking water. Various government entities have instituted water quality limits to protect aquatic life as well. Many countries have created national environmental protection agencies (EPA) that have been designated for this and other environmental-regulating purposes, and in some cases, national governments have delegated this authority to provincial, state, or regional authorities to oversee water quality monitoring and regulation².
In addition to setting legal limits, these authorities also set schedules to test water quality, set standard methods for the maintenance of water systems, and determine which methods for treating contaminated water are acceptable³.
Water quality guidelines are based upon effects that have been observed in both humans and animals for various chemicals and contaminants, and then limits are set at much lower levels than the observed problematic concentrations. The intention of these guidelines is to protect the most sensitive individuals within a given population⁴.
Field equipment may be used to measure water quality at a particular site, but in order to obtain the most accurate assessment, such analysis of collected water samples should occur in a chemical lab⁴.
Once the desired water quality level is observed, scientists then work backwards to determine the maximum concentration that will be allowed in wastewater discharges, and then to develop the standard allowable level based on that amount. Depending on the desired water use, different discharges under different environmental conditions may have different water quality standards².
Common water quality parameters that are used for assessment include aesthetic qualities, cyanide, hardness, fecal coliform, total dissolved solids (salts), trace metals, nutrients, dissolved oxygen, toxicity and organic chemicals⁴. A more complete list of commonly used water quality parameters can be found here.
Under circumstances where rigorous water quality assessment is not possible, watershed or river basin management boards can help to prioritize which water bodies need the most attention and protection².