To define the contamination or any negative impact of contamination, we need to be able to define and measure the pollutants in a sample of water. However, it is neither possible to measure every pollutant in each water sample, nor is it necessary to do so. Therefore, water quality parameters are defined, keeping in view the end use of the water sample, e.g. drinking, outdoor bathing, irrigation, industrial use, for boilers and so on. The same type of pollution may require the use of different water quality parameters depending upon the specific use the water sample is targeted for. Several different classifications of water quality are therefore possible. The classification based on the state of the parameter has three main groups: Physical, chemical and biological.
As for example, water quality parameters for drinking water samples can be divided into two major groups. The first one includes parameters that are important due to their adverse effects on human health. These are heavy metals, toxic substances, bacteria and other pathogenic bodies, turbidity, pharmaceuticals and other potential health-disrupting agents. The second group consists of parameters that are not necessarily health related, but can be a concern for human consumption, like temperature, taste, colour, odour, salinity, pH etc.