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CAN ABIOTIC (INORGANIC) PROCESSES ACCOUNT FOR HALOACETATE CONCENTRATION PROFILES?
Citation:
Urbansky*, E T. CAN ABIOTIC (INORGANIC) PROCESSES ACCOUNT FOR HALOACETATE CONCENTRATION PROFILES? Presented at American Water Works Association Water Quality Technology Conference, Seattle, WA, 11/10-13/2002.
Description:
Haloacetates comprise about 13% of the measurable halogenated organic matter in potable water supplies after chlorination. Some of these species have been linked with animal carcinogenesis and are regulated under the Stage 1 DBP Rule. However, it is known that post-disinfection pre-distribution concentrations do not necessarily reflect concentrations at the tap. Predicting DBP concentrations is complicated by the continuous formation and interconversion of DBPs in the distribution system, but integral for developing sound compliance strategies to meet DBP regulations. Whether the concentrations of haloacetates and halomethanes reach their maxima at the same time and location has been a continued source of debate in drinking water chemistry. This report highlights the need for fundamental understanding of mechanisms and kinetics for reactions (i.e., nucleophilic substitution, hydrolysis, and decarboxylation) that occur in the distribution system and whose rates can be readily measured in the laboratory. Rate constants and activation energies thus determined can then be applied directly in modeling the fate of DBPs. Calculations based on kinetic models in the literature suggest that rates of strictly inorganic (abiotic) chemical decomposition are too small to have detectable impacts and offer further support for the hypothesis that biodegradation is perhaps the most important factor affecting haloacetate loss in the distribution system. Existing chemical literature is critically reviewed, reanalyzed, and applied to potable water. Research aimed at closing gaps in the knowledge base will improve predictive modeling, strengthen the knowledge base for future drinking water regulations, and aid in the creation of sound, cost-effective compliance strategies that meet utilities? needs.