The Influence of Algal Growth and Other Ecological Factors in Reservoirs on the Production and Control of Trihalomethane Precursors

摘要

The objective of the research was to assess the importance of biological activity in a reservoir in altering the nature of the dissolved organic carbon (DOC) content, especially that portion of the DOC that serves as precursors for trihalomethanes (THMs), such as chloroform, that form when water is disinfected with chlorine during drinking-water treatment processes. The study also sought to evaluate the effectiveness of alum coagulation for removing THM precursors. Lake water was fractionated into its hydrophilic and hydrophobic solubility classes; these fractions were analyzed for the DOC content and THM-formation potential. Algal productivity and extracellular product during a six-hour period was determined, and the incubated lake-water samples were also fractionated. Diurnal studies were made to relate primary productivity and extracellular product to daily variations in the lake's DOC concentrations and THM-formation potential. Results showed that the majority of lake water DOC and THM-precursors were hydrophobic in nature. The diurnal studies provided strong evidence that both the algal and heterotrophic populations are involved in the production of THM precursors. Aluminum sulfate was moderately effective for removing THM precursors from lake water. There seemed to be no relationship between alum's effectiveness and the population densities of algae and bacteria, but the effectiveness on a diurnal basis as algal growth varied was not evaluated.