Reduction of organic substances and microorganisms in water by gamma-irradiation

Potable water is indispensable for the existence of people, and it must be clean and safe. The recent problems related to the water sources for water services and water quality have become social problems such as methane trihalide and had smell substances. In the field of water treatment, the effect of radiation on sewage sludge has been studied, and recently, the improvement of the treatment efficiency by the combined use of ozone and radiation has been reported. In this paper, the reduction of the precursor that highly contributes to the production of methane trihalide by irradiation and the interaction of sterilization effect by the combined use of radiation and chlorine are reported. The tested precursors are humic acid, resorcinol, methylglyoxal, phloroglucin and pyruvic acid aqueous solutions. For gamma ray irradiation, a Co-60 source was used. As the measurement of irradiation effect, the amount of total organic carbon was measured, and its tendency of decrease with irradiation time was examined. The measurement of the number of bacilli was carried out with a water sampler. In all test solutions, the TOC decreased by gamma ray irradiation, and the presence of chlorine promoted the effect. (Kako, I.)