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The objective of this study was to characterize thereactivity of disinfection byproduct (DBP) precursors occurring in a water distribution system (DS) and to evaluate the global effect ofresidence time on modified organic matter (MOM) reactivity. The paper discusses a case study of Quebec City's (Canada) water utility distribution system. Four samplingpoints were selected for data collection. The first was located before post-chlorinationwithin the plant. This point provided information about the initial conditions of MOM.The three other points were located along distribution pipes, i.e. at the beginning, themiddle and the extremity, with approximate residence times of water of 3, 12 and 15hours, respectively. The location of these points allowed evaluation of the impact ofresidence time on the formation of DBPs and changes in MOM throughout the pipes.Four sampling campaigns were conducted at each point. In order to characterize MOM reactivity, samples were first concentrated by reverseosmosis until a volume concentration factor of 10 was reached. Fouling organic matterremaining on the membrane was recovered by an alkaline solution wash. Theretentate and the alkaline solution were considered as two distinct fractions. A portion ofthe retentate was fractionated with two non-ionic macroporous resins. The methodology developed for the fractionation was inspiredfrom the method used by L. Labouyrie-Rouiller and the adsorption of the organicmatter was conducted following manufacturer recommendations. MOM reactivity was investigated using experimental chlorination tests on fractionatedand non-fractionated samples under controlled conditions of pH, temperature andchlorine dose. Measurements ofpH, conductivity, turbidity, total organic carbon (TOC), UV-absorbance and temperaturewere carried out for all samples collected and all produced fractions. Includes 14 references, figures.

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Edition: Vol. - No. Published: 11/15/2004 Number of Pages: 10File Size: 1 file , 2.1 MB