Factors affecting formation of disinfection by-products during chlorination of Cyclops

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Courtesy of IWA Publishing

Effects of reaction time, chlorine dosages, pH, temperature and ammonia concentrations on the formation of disinfection by-products (DBPs), including trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), haloketones (HKs), chloral hydrate (CH), and chloropicrin (TCNM), were investigated during the chlorination of Cyclops metabolite solutions containing 4 mg/L (as total organic carbon). Increased reaction time, chlorine dosage, and temperature improved the formation of the relatively stable DBPs, such as trichloromethane (TCM), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), and CH. Formation of nitrogenous DBPs (N-DBPs), including dichloroacetonitrile (DCAN) and TCNM, followed an increasing and then decreasing pattern with prolonged reaction time and increased chlorine dosages, and 1,1,1-2-trichloropropanone (1,1,1-TCP) decreased continuously with increasing reaction time. The amounts of N-DBPs and HKs decreased with increasing temperature. pH affected DBP formation differently, with TCM increasing, DCAA, TCAA, DCAN, and 1,1,1-TCP decreasing, and other DBPs having maximum concentrations at pH 6–7. The formation of most DBPs can be suppressed with increasing ammonia concentration. TCM, CH, TCNM, and 1,1,1-TCP concentrations were always low under all conditions at the level of 0.02–2.39 μg/L.

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