Factors Affecting the Formation and Decay of Trihalomethanes and Haloacetic Acids in a Full-Scale Drinking Water Distribution System
Public Deposited- Last Modified
- February 28, 2019
- Creator
-
Nichols, Cora
- Affiliation: Gillings School of Global Public Health, Department of Environmental Sciences and Engineering
- Abstract
- The formation and decay of trihalomethanes (THMs) and haloacetic acids(HAAs) were evaluated in a full-scale distribution system where free chlorine and combined chlorine were used as secondary disinfectants. The distribution system was monitored over a 4-month period, while the utility switched from combined chlorine to free chlorine for a one-month period and then back to combined chlorine. A distribution system model was used to identify 14 sample sites representing a wide variety of point of use attributes including residence time, pipe diameter, and pipe material. The results show that free chlorine dissipated in the distribution system proportionally to residence time, while the combined chlorine residual remained stable. The disinfection by-product (DBP) concentrations in the distribution system varied with disinfectant type, dose, and contact time. Free chlorine disinfection produced significantly higher DBP concentrations than combined chlorine. DBP concentrations were relatively stable throughout the distribution system during chloramination, but continued to increase with increasing residence time during chlorination. The THM concentration increased more significantly than the HAA concentration as residence time increased. Accordingly, the THM to HAA ratio increased with increasing residence time during chlorination. There was no discernable impact of pipe diameter or pipe material on DBP formation or decay. No biological degradation of HAAs was observed during this study. HPC concentrations were unaffected by the switch from combined chlorine to free chlorine. No evidence of nitrification was observed during the course of the study.
- Date of publication
- May 2004
- DOI
- Resource type
- Rights statement
- In Copyright
- Advisor
- DiGiano, Francis A.
- Weinberg, Howard
- Singer, Philip
- Degree
- Master of Science in Environmental Engineering
- Academic concentration
- Environmental Engineering
- Degree granting institution
- University of North Carolina at Chapel Hill
- Graduation year
- 2004
- Language
- Deposit record
- 8daa46ae-58bd-4ddf-8097-0c44062f7d48
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