Low Cost Approach for Dechlorination
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Chlorine has been used for many years to treat municipal and industrial water and wastewater. The basic reasons for using chlorine in the treatment of wastewater is the destruction of inherent pathogenic organisms, bacteria and viruses to prevent the spread of disease by water borne agents. However, there is increasing concern and regulation over the levels of residual chlorine in wastewaters that are discharged to the receiving streams. Current regulatory agencies are examining the effect of residual chlorine and chlorinated compounds in water on human and aquatic life. It is not always possible to maintain a low chlorine residual by dose alone. Breakpoint chlorination and wastes with high chlorine demand (for adequate disinfection) may result in a high chlorine discharge. Therefore, it may be necessary to use dechlorination agents to reduce or eliminate residual chlorine levels in wastewaters. Gwinnett County has been concerned about the effects of the potentially toxic nature of chlorine in the treatment plant effluent and its effects on the aquatic life found in the receiving streams. The work that Gwinnett County has done in the past year in constructing a delivery system for sodium thiosulfate shows one means of addressing the dechlorination of wastewater without considerable capital outlay. Other municipalities have study the system that we have installed and are making plans to have a similar system designed because they are to receive new chlorine limits on their N.P.D.E.S. Permits when they are reissued.