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The effect of goethite on the formation of disinfection by-products (DBPs) during chlorination was investigated under various reaction times, pH, and chlorine concentrations. The experimental results indicated that in the presence of goethite, the formation of DBPs was enhanced as pH and chlorine concentration increased. The enhancement of DBP formation could be attributed to the generation of hydroxyl radical (), which could oxidize natural organic matter (NOM) in water and produce more DBP precursors to react with chlorine. X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses of goethite revealed that goethite may adsorb NOM on its surface and modify NOM structure. The reaction mechanisms of goethite-enhanced DBP formation were proposed in three steps: (1) the oxidation of NOM into small molecules available as DBP precursors byfrom the reaction between ferrous ions on goethite surface and chlorine; (2) the adsorption and modification of NOM on goethite surface responsible for increasing chlorine consumption; and (3) the presence of ferric ions on goethite surface promoted the formation of DBPs. [ABSTRACT FROM PUBLISHER]

Formation of typical volatile carbonaceous and nitrogenous disinfection by-products (C-DBPs and N-DBPs) during aqueous monochloramination of oxytetracycline (OTC) was investigated in this study. Impact factors including reaction time, pH, monochloramine (NH2Cl) dosages, and bromide concentrations were examined. The results showed that six DBPs including chloroform, dichloroacetonitrile, trichloronitromethane, 1,1-dichloropropanone, 1,1,1-trichloropropanone, especially extreme toxic N-Nitrosodimethylamine were found. Formation of these DBPs increased over time and monochloramine dosages with maximum yields given as 14.2, 4.3, 0.8, 2.1, 0.7, and 4.1 μg/mg at pH 7, respectively (μg/mg represents DBPs yields per mg of OTC). Solution pH exerted significant influence on the formation of all the DBPs species. Peak yields were found under circumneutral conditions. Production of bromine-substituted DBPs increased in the presence of bromide. Removal of presented OTC in waters should be implemented before chloramination disinfection process in drinking water treatment. [ABSTRACT FROM PUBLISHER]

Yangtze River raw water from Yangshupu Water Plant, Shanghai was studied in this paper for reduced formation potential of chlorination and chloramination disinfection by-products (DBPs) after pre-oxidation by three kinds of common pre-oxidants, whiich were potassium permanganate, chlorine and chlorine dioxide. Results of chlorination showed that removal effectiveness of all the selected oxidants on total chlorination DBPs was not significant, and the reduction percentages by ClO2, Cl2 and KMnO4 were 8.4%, 5.7% and 3.9%, respectively. The order of DBPs control effect was ClO2, > Cl2 > KMnO4. As to Yangtze River raw water in case of chlorine disinfection, using ClO2 as pre-oxidation agent showed relatively better effect on removal of DBPs. However, chloramination results demonstrated that impacts of the three preoxidants on DBPs formation potential were quite different, and the reduction percentages by ClO2 and KMnO4 were 18.1% and 4.1%, respectively, while pre-chlorination increased the potential by 12.3%. These results revealed that ClO2 had the highest removal effectiveness, meanwhile pre-chlorination should be avoided due to its notable increase in DBPs formation.

Twelve typical nitrogenous organic compounds including herbicides, pesticides, amino acids, industrial products etc in polluted raw water were selected to investigate formation of typical carbonaceous and nitrogenous DBPs during chlorination and chloramination. To indentify the formation mechanism of carbonaceous and nitrogenous disinfection byproducts from nitrogenous chemicals, chlorination and chloroamination of urea herbicides, triazine herbicides, amino acid, and other compounds were investigated. As a result, the potential precursors for different DBPs were defined as well. It has been identified that widely used urea herbicides could produce as many as 9 specific DBPs. The chlorotoluron shows highest reactivity and yields chloroform (CF), monochloroacetic acid (MCAA), dichloroacetic acid (DCAA), 1,1-dichloro-acetone (1,1-DCP), 1,1,1-trichloro-acetone (1,1,1-TCP), chloropicrin (NTCM), dichloro-acetonitrile (DCAN), dimethylnitrosamine (NDMA). The results indicated that aldicarb and dinoseb are important precursors of CF, DCAA, MCAA, NTCM as well. High concentrations of CF and DCAA were found during L-tryptophan chlorination. Furthermore, DBPs formation pathways and mechanisms were suggested during chlorination and chloramination of chlorotoluron, ametryn, dinoseb L-tryptophan.