Researches on Formation of Haloacetic Acids in Chlorination of Drinking Water by a Novel Technique

Haloacetic acids(HAAs) are formed during the chlorination of drinking water,which are harmful to people′s health due to their carcinogenic and mutagenic effects. In the present study,a detection method combining methyl tert -butyl ether(MtBE) extraction with acid catalysis and gas chromatography coupled with an electron capture detector(GC/ECD) was developed for determining HAAs. The detection limit of this method(MDL) and relative standard deviation(RSD) were below 0.37 μg/L and 6.2%,respectively. The laboratory chlorination experiments were conducted with the purpose of investigating the influences of reaction time,temperature,UV_ 254 ,bromide and ammonia-nitrogen on the formation of HAAs. The results show that the formation amount of HAAs increases with increasing reaction time and temperature,respectively;and there exists a linear relationship between the formation of HAAs and UV_ 254 . The formation amount of HAAs decreases first and then increases as the bromide ion concentration increases,and adding NH +_4 is a possible way to control the formation of HAAs.

Formation of iodo-trihalomethanes, iodo-haloacetic acids, and haloacetaldehydes during chlorination and chloramination of iodine containing waters in laboratory controlled reactions

Iodine containing disinfection by-products（I-DBPs） and haloacetaldehydes（HALs） are emerging disinfection by-product（DBP） classes of concern. The former due to its increased potential toxicity and the latter because it was found to be the third most relevant DBP class in mass in a U.S. nationwide drinking water study. These DBP classes have been scarcely investigated, and this work was performed to further explore their formation in drinking water under chlorination and chloramination scenarios. In order to do this, iodo-trihalomethanes（I-THMs）,iodo-haloacetic acids（I-HAAs） and selected HALs（mono-HALs and di-HALs species, including iodoacetaldehyde） were investigated in DBP mixtures generated after chlorination and chloramination of different water matrices containing different levels of bromide and iodide in laboratory controlled reactions. Results confirmed the enhancement of I-DBP formation in the presence of monochloramine. While I-THMs and I-HAAs contributed almost equally to total I-DBP concentrations in chlorinated water, I-THMs contributed the most to total I-DBP levels in the case of chloraminated water. The most abundant and common I-THM species generated were bromochloroiodomethane, dichloroiodomethane, and chlorodiiodomethane. Iodoacetic acid and chloroiodoacetic acid contributed the most to the total I-HAA concentrations measured in the investigated disinfected water. As for the studied HALs, dihalogenated species were the compounds that predominantly formed under both investigated treatments.

Halogen-specific total organic halogen analysis： Assessment by recovery of total bromine

Determination of halogen-specific total organic halogen（TOX） is vital for studies of disinfection of waters containing bromide, since total organic bromine（TOBr） is likely to be more problematic than total organic chlorine. Here, we present further halogen-specific TOX method optimisation and validation, focusing on measurement of TOBr. The optimised halogen-specific TOX method was validated based on the recovery of model compounds covering different classes of disinfection by-products（haloacetic acids, haloacetonitriles,halophenols and halogenated benzenes） and the recovery of total bromine（mass balance of TOBr and bromide concentrations） during disinfection of waters containing dissolved organic matter and bromide. The validation of a halogen-specific TOX method based on the mass balance of total bromine has not previously been reported. Very good recoveries of organic halogen from all model compounds were obtained, indicating high or complete conversion of all organic halogen in the model compound solution through to halide in the absorber solution for ion chromatography analysis. The method was also successfully applied to monitor conversion of bromide to TOBr in a groundwater treatment plant. An excellent recovery（101%）of total bromine was observed from the raw water to the post-chlorination stage. Excellent recoveries of total bromine（92%–95%） were also obtained from chlorination of a synthetic water containing dissolved organic matter and bromide, demonstrating the validity of the halogen-specific TOX method for TOBr measurement. The halogen-specific TOX method is an important tool to monitor and better understand the formation of halogenated organic compounds, in particular brominated organic compounds, in drinking water systems.