Chlorination is an efficient and low-cost technique in disinfecting water for\npublic water supply. However, during the process, the formation of undesirable\nby-products called halogen compounds, such as trihalomethanes (THMs),\noccurs. Some of these compounds are proven to be carcinogenic to laboratory\nanimals. The goal of this study was to investigate the occurrence of THMs in\nhousehold reservoirs and the influence of cleaning time of these reservoirs on\nthe formation of THMs. A total of 103 households were investigated in the\ncity of Maringa, State of Parana, Brazil. The residences were classified according\nto the cleaning time of the reservoir into: up to one year, one to two\nyears and more than two years. Samples were taken from the reservoirs and\ntotal trihalomethanes (THMt) were analyzed by gas chromatography\n(GC-MS), total organic carbon (TOC) by means of a Hach kit for low concentrations\nand free residual chlorine (CLres) by means of a kit for in loco\ndetermination. According to the results, the highest concentrations of THMt\nwere observed in the reservoirs with cleaning time of more than 2 years.\nHowever, no amount has exceeded the maximum limit allowed by law. In\ngeneral, the longer the time for cleaning the reservoir, the greater the degradation\nof water quality in THMt.
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