AWWA JAW10892

This study was conducted to clarify further the roles that algae and heterotrophic organisms could play in altering the nature and abundance of trihalomethane (THM) precursors present in the pool of soluble organic carbon in reservoirs. Some investigators felt that there were definite, seasonal variations in drinking water THM formation potential (THMFP), with the greatest variation during the warmer months. Others have evaluated the significance of reservoir algae as contributors to the THM-precursor pool. Alum coagulation reduced THM precursors by about 50 percent, and its effectiveness did not appear to be altered by variations in algal or bacterial population densities in the lake. Yields of THMs from the dissolved organic carbon that remained after treatment, however, were generally greater when biological activity in the reservoir was high. Diurnal variations caused by intense biological activity could affect the ability of a water treatment plant to produce water with THM levels consistently less than the maximum contaminant level. Includes 18 references, tables, figures.