A preliminary study on removing THMs from chlorinated water by ozonation ( " O 3 " process) and granular activated carbon bed filtration and adsorption ("AC" process) was carried out. It was found that the chloroform content In chlorinated water was reduced to some extent by ozonation at low dosages, but then It Increased steeply with time, and finally reached much higher than the original values.The GAC beds In both the "AC" and " O 3 + AC" processes were found to be effective in removing chloroform by adsorption during their early operating period, corresponding to 4,000 -5,000 bed volumes throughput, or one month duration for carbon X-ll and carbon ZJ-15 beds 1n the "AC" process. With preozonation. I.e., the " O 3 + AC" process, the operating period with positive chloroform removal effi ciencies was tripled. Nevertheless, the chloroform content 1n effluents from the GAC bed 1n both processes Increased with operating time and throughput, and finally became much higher than the level In the Influents. The phenomenon presumably was due to three mechanisms occurring 1n the carbon beds: 1) the biodégradation of complex chlori nated compounds Into THMs; 2) the anaerobic digestion products can react with free chlorine 1n water to form THMs; 3) the desorptlon of THMs adsorbed on the carbon surfaces.In order to prevent the treated water from producing high concentrations of THMs, chlorlnatlon should be avoided before either the "AC" or the "Og + AC" process. Home use carbon filters also are recommended to be used carefully and reasonably, for they can Increase THM concen trations 1n effluents to levels much higher than those In the Influents after a certain time of operation.
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