Assessment of trihalomethane formation in chlorinated raw waters with differential UV spectroscopy approach.

In this study, the changes in UV absorbance of water samples were characterized using defined differential UV spectroscopy (DUV), a novel spectroscopic technique. Chlorination experiments were conducted with water samples from Terkos Lake (TL) and Büyükçekmece Lake (BL) (Istanbul, Turkey). The maximum loss of UV absorbance for chlorinated TL and BL raw water samples was observed at a wavelength of 272 nm. Interestingly, differential absorbance at 272 nm (ΔUV₂₇₂) was shown to be a good indicator of UV absorbing chromophores and the formation of trihalomethanes (THMs) resulting from chlorination. Furthermore, differential spectra of chlorinated TL waters were similar for given chlorination conditions, peaking at 272 nm. The correlations between THMs and ΔUV₂₇₂ were quantified by linear equations with R² values >0.96. The concentration of THMs formed when natural organic matter is chlorinated increases with increasing time and pH levels. Among all THMs, CHCl₃ was the dominant species forming as a result of the chlorination of TL and BL raw water samples. The highest chloroform (CHCl₃), dichlorobromomethane (CHCl₂Br), and dibromochloromethane (CHBr₂Cl) concentration were released per unit loss of absorbance at 272 nm at pH 9 with a maximum reaction time of 168 hours and Cl₂/dissolved organic carbon ratio of 3.2

Relationship among chlorine dose, reaction time and bromide ions on trihalomethane formation in drinking water sources in Istanbul, Turkey

We investigate the effects of factors such as chlorine dose, reaction time and bromide ions on the formation and speciation of trihalomethanes during the chlorination of Istanbul reservoirs such as Terkos lake water, Büyükçekmece lake water and Ömerli lake water. The experimental results showed that approximately 50% of trihalomethane formation was observed in the first 4 h of reaction time in chlorinated Terkos lake water, Büyükçekmece lake water and Ömerli lake water, respectively. Trihalomethane concentrations increased with increasing chlorine dosage and reaction time. Chloroform was the major trihalomethane species forming as a result of the chlorinated raw water samples. On the other hand, bromide ions play a great significant role in the distribution of trihalomethane species. The bromine and chlorine incorporation ratios were strongly related to natural organic matter precursors and bromide levels in Terkos lake water, Büyükçekmece lake water and Ömerli lake water. The percentage of bromine incorporation was much higher than that of chlorine in all chlorinated water samples

Experimental investigation of trihalomethane formation and its modeling in drinking waters

This research developed models using multiple linear regression analysis for the prediction of trihalomethane formation in coagulated Istanbul drinking water sources. The power-law model (model 1), using only ΔUV272 as the designed parameter, proved the best model to describe the formation of trihalomethane. The other model (model 2), included pH, total organic carbon, chlorine dosages, ultraviolet absorbance at 254 nm (UV254), specific ultraviolet absorbance (SUVA) and differential absorbance at 272 nm (ΔUV272). The root-meansquare error (RMSE), normalization mean square error (NMSE), regression coefficient (R2) and index of agreement (IA) were used as statistical variables to evaluate the model performance. The better prediction results were obtained by model 1 for root-mean-square error, normalization mean square error, R2 and index of agreement as 9.14, 0.015, 0.95 and 0.99, respectively. © 2015, Chemical Publishing Co. All rights reserved