The disadvantage of chlorination of drinking water is the possible synthesis of toxic chlorinated fragments. In different cases UV can be an alternative to chlorination. The germicidal effectiveness of UV#x2013;radiation is in the 180#x2013;320 nm region with an optimum at 265 nm. Approximately 95 of the energy radiated by a low#x2013;pressure mercury arc is at the 253.7 nm line, so this source is the most effective one for germicidal applications. The germicidal effectiveness of a broadband source can be calculated. UV alone cannot decrease the concentrations of organic contaminants of the treated water. Quite promising are the systems where UV#x2013;radiation acts as a catalyst in oxidation reactions in order to decrease the organic contaminants.
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