Volatile organic compounds in streams near wastewater outfalls, Rockdale County, Georgia, 2002–2004

Abstract

The U.S. Geological Survey operates a wa-ter-quality and water-quantity monitoring network in Rockdale County, Georgia. The program was established to provide data to monitor water-quality changes brought about by increasing urbanization in the county. Water-quality samples have been collected since November 2002 from 13 sampling sites distributed among the five major watersheds of the county. Samples are collected and ana-lyzed for a variety of inorganic and organic constituents, including many U.S. Environmental Protection Agency (USEPA) priority pollutants. One goal of the program is to monitor point-source pollution from wastewater treatment plant outfalls in Rockdale County. To accomplish this goal, one back-ground site is sampled upstream from an outfall and four sites are sampled downstream from wastewater outfalls. One hundred and eleven samples were collected from these five sites and were analyzed for a full suite of USEPA priority pollutants including a combination of inorganic and organic constituents, volatile organic com-pounds (VOCs), semivolatile compounds, and pesticides. The scope of this paper is limited to the 66 VOCs ana-lyzed. Of the eight VOCs detected, six likely result from the chlorination of wastewater. Trihalomethanes (THMs) are disinfection by-products resulting from chlorination of drinking water as well as wastewater. At elevated concen-trations in drinking water, these compounds can be delete-rious to human health. The two remaining compounds are methyl tert-butyl ether, a gasoline additive, and toluene, an organic solvent. The VOCs concentrations ranged from 0.1 to 1.6 micrograms per liter and were all below drink-ing-water standards.