Water quality standards

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Water quality

The term water quality has to do with the description of given water in terms of its characteristics. Characteristics of water quality include temperature; concentrations of various kinds of particles; concentrations of dissolved materials; and parameters such as turbidity, pH, color, conductivity, etc. The term characteristic is more inclusive than the term contaminant and would include temperature, color, turbidity, conductivity, etc. Two of these categories of characteristics, i.e., particles and dissolved materials, would include thousands of species each. A particular combination, or set, of characteristics would comprise a water quality profile.

Those contaminants that interfere with a particular use may be considered pollutants. To add further to the definitions that circle about the same idea, the term parameter is used frequently. Water quality parameters might include temperature, BOD, pH, specific electrical conductance, UV254 absorbance, etc. With respect to uses of water, the terms criterion and standard are important. A water quality criterion is a contaminant concentration limit that, if exceeded, may impair a use or cause a toxic effect in certain animals or plants. As an example, a boron limit of 0.5 mg=L is considered appropriate for citrus crops. A criterion could also specify a contaminant or parameter range, e.g., 3,3 ≤ pH ≤ 10,7 for trout (McKee and Wolfe, 1963, p. 236). A water quality standard is a quasi-legal limit for a contaminant concentration or parameter value, i.e., the value may be referenced in a law but may be either ‘‘recommended’’ or ‘‘enforced,’’ depending upon the severity of the effects and the levels that are economically achievable. Usually, there is nothing absolute about the foregoing definitions.

Table 2.1 illustrates a water quality description (надо ли вставлять сюда в качестве примеров наши стандарты из СанПиН и т.п.???) for a proposed industrial waste discharge. Points of interest in Table 2.1 are (1) some 37 contaminants are listed; (2) concentration limits are shown for each contaminant; (3) two places for discharge—a publicly owned treatment works and a river— are shown, each with its own respective discharge limits; (4) limits are given in terms of the monthly average and the daily maximums; (5) a variety of organic compounds are listed; and (6) a variety of heavy metals are listed. Each treatment situation is different and would have a different list of contaminants and different limits. A similar tabular description, but with different constituents, would apply to a municipal wastewater discharge, a drinking water treatment plant product water, or another industrial waste situation [Hendricks David W. Fundamentals of water treatment unit processes physical, chemical and biological]

Water quality standards

A criterion becomes the basis for a standard, which is a codified criterion. Water quality standards have evolved over the decades of the twentieth century. Usually, standards are normative in character, i.e., dependent not only on effects on uses but on economic and cultural factors.

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