Effect of ferric and bromide ions on the formation and speciation of disinfection byproducts during chlorination

The effects of ferric ion, pH, and bromide on the formation and distribution of disinfection byproducts （DBPs） during chlorination were studied. Two raw water samples from Huangpu River and Yangtze River, two typical drinking water sources of Shanghai, were used for the investigation. Compared with the samples from Huangpu River, the raw water samples from Yangtze River had lower content of total organic carbon （TOC） and ferric ions, but higher bromide concentrations. Under controlled chlorination conditions, four trihalomethanes （THMs）, nine haloacetic acids （HAAs）, total organic halogen （TOX） and its halogen species fractions, including total organic chlorine （TOC1） and total organic bromide （TOBr）, were determined. The results showed that co-existent ferric and bromide ions significantly promoted the formation of total THMs and HAAs for both raw water samples. Higher concentration of bromide ions significantly changed the speciation of the formed THMs and HAAs. There was an obvious shift to brominated species, which might result in a more adverse influence on the safety of drinking water. The results also indicated that high levels of bromide ions in raw water samples produced higher percentages of unknown TOBr.

Characteristics of Trihalomethanes in Water Distribution System

To investigate the characteristics of disinfection by-products （DBPs） in an actual water distribution system using the raw water with high bromide ion concentration, the composition and concentration of trihalomethanes （THMs） formed by chlorination of the water in the presence of bromide ion were measured in a city water distribution system during one year. The results show that brominated THMs contributed a great part （83%-89% ） to the index for additive toxicity （ATI） and resulted in the ATI of most of the samples exceeding WHO guideline standard for total THMs （ TTHMs）, especially during the summer （ rainy season）. This indicates that the chlorination of water in the presence of bromide ion leaded to high ratios of brominated THMs to TrHMs. However, a visible increase in the concentration of THMs with increasing residence time in the distribution system was not observed. Additionally, based on alternatives analysis, packed tower aeration method is proposed to reduce THMs level of the finished water leaving the treatment plant.

Effects of Br−on NDMA Formation During Chloramination:a Review of Influencing Factors,Mechanisms,and Control

For the invasion of seawater and the stress of human activities,bromide ion(Br−)exists widely in drinking water sources,and it was found to influence the formation of non-brominated but carcinogenic nitrogen-containing disinfection by-product nitroso-dimethylamine(NDMA)during chloramination(NH2Cl).The presence of Br−leads to the formation of bromine-active species,such as bromamines(NH2Br),bromochloramine(NHClBr),as well as hypobromous acid(HOBr),which are more reactive with NDMA precursors than chlorine-active species,so might promote NDMA generation.This review mainly focuses on the influencing laws,as well as the factors(disinfection conditions and characteristics of water matrixes)that affected NMDA formation during chloramination with Br−.In addition,the possible influencing pathways are discussed.Finally,based on the above summary,measures pertaining to reduce the impact of Br−on NDMA production are concluded.This review would provide a theoretical reference for drinking water treatment plants to deal with bromine-containing water during chloramination.

Degradation of dibromophenols by UV irradiation

We examined the degradation of dibromophenols （DBPs）, i.e. 2,4-DBP, 2,6-DBP and 3,5-DBP by ultraviolet （UV） irradiation and estimated the relationship between degradability and molecular orbital properties of each dibromopbenol. The removal of DBPs under a UV lamp system was successfully performed in an aqueous solution. After 5 min of irradiation, the initial DBPs concentration of 20 mg/L was decreased to below 1 mg/L, and about 60% of bromide ion was released. A decrease in the concentration of dissolved organic carbon （DOC） suggested the mineralization of DBPs, The mineralization may occur after release of bromide ions because the decrease of DOC was slower than the release of bromide ions. The degradability of 3,5-DBP was slightly lower than 2,6-DBP and 2,4-DBE Molecular orbital calculation suggested that the electrophilic frontier density and the highest occupied molecular orbital （HOMO） energy may be related to the degradability of DBPs.