Treatability Assessment of Jordan Lake as a Drinking Water Source
Creators: name: Miller, Kathryn L.
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 1992

description: Jordan Lake, located in Chatham County in central North Carolina, was built by the Army Corps of Engineers in 1980 for flood control and recreational use. Prompted by steadily growing development in the area with increasing demands on existing water supplies, Jordan Lake is currently being considered as a drinking water source for several nearby communities. Tributaries to Jordan Lake drain industrial and urban centers, and samples from these sources have demonstrated toxicity in several bioassays. Elevated concentrations of metals and the presence of synthetic organic chemicals in one of the tributaries have raised concerns over the suitability of the lake as a source of drinking water. Classified by the N.C. Department of Environmental Management as eutrophic, Jordan Lake water contains relatively high concentrations of total organic carbon (TOC) and humic material. When treated with oxidants and disinfectants, humic substances may react to form compounds generally referred to as disinfection byproducts (DBFs). Trihalomethanes (THM), a class of potentially carcinogenic reaction products from the chlorination of aquatic humic material, have been regulated in drinking water by the U.S. Environmental Protection Agency since 1979. New maximum contaminant levels (MCLs) in drinking water for these and other DBFs will soon be announced. In assessing the suitability of Jordan Lake as a drinking water supply, it is important to determine the possible presence of harmful impurities in the water as well as to evaluate the potential formation of DBFs from various treatment processes. The primary objective of this research was to test three treatment process trains for Jordan Lake water and to compare the finished water quality from each of the trains. Conventional surface water treatment consisting of coagulation, sedimentation and filtration was applied to samples of the raw water collected during four different seasons. Part of the filtered water was then disinfected with chlorine. Another portion was filtered through granular activated carbon followed by disinfection with chlorine. A third portion was treated with ozone followed by the addition of monochloramine. These three processes were applied to four samples of Jordan Lake water during one year and to four samples from Falls Lake near Raleigh, N.C., for purposes of comparison. Falls Lake is currently used as a source of drinking water for the City of Raleigh. Water quality and treatment effectiveness were measured in terms of turbidity reduction, TOC removal, formation of THM and total organic halides (TOX), and Ames mutagenicity. The Ames genotoxicity bioassay is a method of assessing the collective presence of harmful compounds without analyzing for specific chemicals. Results from this assay indicate a relative level of genetic mutation potential in the whole sample rather than from any specific compound. The Ames bioassay has demonstrated a high degree of sensitivity towards mutagenic compounds associated with raw and treated drinking waters. Some chlorinated organic byproducts in drinking water have been found to be mutagenic at nanogram per liter (ng/1) concentrations. Researchers have used the assay to detect the presence of synthetic organic chemicals in waters at levels that are below the limits of detectability by modern chemical methods of analysis.