Decrease in the chloride disinfection by-products (DBPs) formation potential in water as a result of coagulation process

The efficient removal of natural organic matter reduces the potential for by-products that are formed during the process of disinfection. Among the various organic derivatives, the following are listed: halogenoacetonitriles, halogenonitromethanes, halogenoketones and most commonly trihalogenomethanes. The aim of the study was to determine the effect of coagulation process on the change of selected 12 chlorine disinfection by-products (DBPs) formation potential. The coagulation process was carried out with aluminium(VI) sulphate and four pre-hydrolyzed aluminium salts. Among the halogenoacetonitriles (HAN), the following compounds were analyzed: trichloroacetonitrile (TCAN), dichloroacetonitrile (DCAN), bromochloroacetonitrile (BCAN) and dibromoacetonitrile (DBAN). The trichloronitromethane, otherwise known as chloropicrin (CP) and halogenoketones (HK): 1,1-dichloropropanone (1,1-DCP) and 1,1,1-trichloropropanone (1,1,1-TCP) were also analyzed. Among trihalogenomethanes (THM) trichloromethane (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), tribromomethane (TBM) were analyzed. Furthermore, one compound of trichloroacetaldehyde (chloral hydrate [CH]) was identified, too. Quantitative and qualitative analysis was carried out using gas chromatograph-mass spectrometry (GC-MS). The results of the chlorine potential test indicate that the coagulation efficiency depended on the type of coagulant. The most effective coagulant was one of pre-hydrolyzed salt (FLOKOR 1ASW/B). Addition of FLOKOR 1ASW/B resulted in reduced DBPs formation potential of 60%-82% compared with the raw water.