Effects of typical nitrogenous compounds on trihalomethanes formation and chlorine demand during drinking water chlorination

Glycine （ Gly）, cysteine （ Cys）, aspartic acid （ Asp）, leucine （ Leu）, lysine （ Lys ）, and methyl amine （MA） were chosen as typical nitrogenous compounds, and the effects of them on trihalomethanes （THMs） formation and chlorine demand were performed on filtrated water. Results show that the nitrogenous compounds enhance THMs formation, and the increased levels are controlled by characteristics and the concentration of nitrogenous compounds. The increase in THMs formation follows the order of Asp （126 μg/L） 〉 Cys （119 μg/L） 〉 MA（ 106 μg/L） 〉 Lys （ 97 μg/L ） ≈ Gly （ 96 μg/L ） 〉 Leu （ 80μg/L ） （ while nitrogenous compounds = 1.0 mg/L, and background THMs = 60 μg/L）. The increase in chlorine demand is approximately proportionate to the content of nitrogenous compounds, which illustrates that the increase is mainly caused by the reaction of nitrogenous compounds with chlorine. And the increase in chlorine demand follows the order of Cys（ 27. 8 mg/ L） 〉Asp（22.6 mg/L） = Gly（22.6 mg/L） 〉Lys（21.6 mg/L） 〉 MA（14. 1 mg/L） 〉 Leu（11.8 mg/L） （while nitrogenous compounds = 1.0 rag/L, and background chorine demand = 1.8 mg/L）. The mechanisms of nitrogenous compounds enhancing THMs formation are summ the increase of chlorine demand raising THMs formation in reaction of NOM with chlorine, and the THMs formation in chlorination of nitrogenous compounds themselves.