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Natural discoloration of freshwater: chemical composition and environmental genesis

are most commonly referred to as discoloured or simply coloured water. On aesthetic grounds alone coloured water is undesirable for domestic use, and accordingly the EC standard for acceptable drinking water is 1.5 au-1m-1 (at 400 nm-1). The visual factor is not the only objection. It has been claimed that the materials responsible for colour impart taste to water, reduce chlorination efficiency, and by acting as a nutrient source encourage bacteria in the water. In addition, certain industries, in particular food processing, brewing, distilling, textiles and pulp and paper manufacture, are concerned about the colour of the water they use and its possible effect on their products. There is no evidence that coloured water is directly harmful to health. However, it is possible that through the solubilization of trace metals, such as lead and cadmium, a coloured water could, over a long period of time, have a chronic health effect. It has been found that the chlorination of waterborne organics, such as humic and fulvic acids, is responsible for the production of mutagens (Meier et al., 1985; Hemming et al.. 1986). Steelink (1977) has associated increased incidences of bladder cancer with the production of chloroform from the chlorination of humic acids.