Study On The Determination And Formation Of Chlorination Disinfection By-products In Drinking Water

The illnesses attributable to waterborne pathogens were greatly reduced since the use of chlorination disinfections. Unfortunately it produced another harmful substance, named chlorination disinfection by-products (DBPs) that mainly come from the reaction between chlorination disinfection reagent and organic compounds in water. DBPs are categorized as trihalomethanes, haloaceticacids, chalkstones, chlorophenols and haloacetonitriles etc, which are proved harmful to human being, and some even listed in probably carcinogenic to humans.Two quantitative methods, one for chloroacetic acids and another for chlorophenols were proposed in this dissertation. Firstly, a gas chromatographic method for the determination of dichloroacetic acid and trichloroacetic acid in drinking water was established. In acidified sample the chloroacetic acids were adsorbed on the D101 macroporous resin, then eluted with acetonitrile by the combination of the static and dynamic elution. The eluted solution was concentrated by evaporation in a rotary evaporator. The analyte was esterified in sulfuric acid-methanol solution and extracted with methyl tertiary-butyl ether (MTBE) and determined by gas chromatography with ECD detector. The proposed method was applied to tap water analysis with the recovery in the range of 85% ~ 113.7% and RSD rangede from3.78%~5.27%. The detection limit was 0.14ng for DCAA and 0.03ng for TCAA.Secondly, a reverse high performance liquid chromatography wasdeveloped for the simultaneous determination of phenol, 2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol. The influencing factors, such as adsorbent, eluent and enrichment were investigated. The results showed that the optimized chromatographic conditions were as follows: The SHMADZU VP-ODS (5μm, 150mm×4.6mm) was chosen as analytical column, methanol-water (1% acetic acid) as mobile phase and in gradient elution manner and the absorbance measured at 280nm and 295nm. It was found that the analyte loss was greatly reduced provided the eluted solution was concentrated in an alkaline solution. Under the optimized conditions, the method was applied to the determination of chlorophenols in drinking water with the recoveries ranged from 85% to 113.7% and the relative standard deviations ranged from 2.5% to 6.8%.Finally, the simulation experiment of the formation of haloacetic acid was carried out, using the humic acid as the precursor substance, and Javel water as disinfector. The parameters, such as the humic acid concentration, chlorine dose, water temperature, the duration of reaction and the pH value of solution were examined by single factor rotates. The results confirmed that DCAA and TCAA were formed when the Javel water reacted with humic acid in water. It was also found that, within the scope of certain, the contents of chloroacetic acid were elevated with the increase of concentration of humic acid and chlorine dose; it also increased with the rise of water temperature, the duration of reaction and the decrease of pH value.