Water Treatment

Treatment Norms

Minimum standards for drinking water are set by environmental agencies while industries have their own guidelines. Physical characteristics, such as temperature, colour, turbidity (clarity or transparency), odour and taste, are measures of aesthetic acceptability and palatability, the oldest criteria for judging water quality. Micro-organisms, such as pathogenic and coliform organisms, are chemically eliminated to prevent water-borne diseases, but the chemicals must also be monitored because they can be detrimental to human health. Other chemical characteristics include the degree of acidity or alkalinity (the cause of scaling on pipes and household cookware), and concentrations of dissolved solids and oxygen. For example, some prairie natural waters have total-dissolved-solids (TDS) concentrations higher than 1000 mg/L, while the maximum level for Canadian drinking water is 500 mg/L and many industry processes require concentrations which are below 200 mg/L. Concentrations of various radionuclides which may originate from natural sources, nuclear accidents or nuclear power generation, are also monitored.

Processes used

Several physical and chemical processes are available for water treatment. The most common physical processes are screening, flocculation, sedimentation, filtration and adsorption. Distillation and reverse osmosis are used primarily in industrial water treatment. Chemical processes include aeration, coagulation, softening, pH adjustment, ion exchange and disinfection. Disinfection can be accomplished by chlorination, the addition of ozone, heating, exposure to ultraviolet light and the addition of bromine or iodine compounds (for industrial applications). Chlorination is the most common method. An effective germicide, chlorine is also beneficial in colour removal, taste and odour control, suppression of algal growths and the precipitation of iron and manganese.