The primary risk associated with a UV irradiation system is potential exposure of plant personnel to UV irradiation and electrical hazards. Personal training regarding the effects of UV irradiation and protective procedures will minimize these risks. Dechlorination Dechlorination involves contacting the chlorinated effluent with a substance that reacts with or accelerates the rate of decomposition of the residual chlorine. This eliminates the impact of the discharge of chlorinated effluent, thus improving water quality and aquatic habitats in the vicinity of the outfall. The application of sulphur dioxide is by far the most widely used method of dechlorination, particularly in large plants, due to its relatively low cost and availability.
Sulphur dioxide, however, is a toxic, highly corrosive, odorous gas.
Risks associated with its transportation, storage handling and use can be minimized through sound engineering design and safe work practices. Safety standards for equipment design and operating procedures have been developed by the manufacturing industry. Sodium bisulfide can also be used as a dechlorination agent. Sodium bisulfide is a corrosive liquid, and more costly than sulphur dioxide.