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Emerging Contaminants in the Drinking Water Cycle.
Citation:
GLASSMEYER, S. Emerging Contaminants in the Drinking Water Cycle. Presented at Region 3 Emerging Contaminants Webcast, The Web, Newark, NJ, April 15, 2009.
Impact/Purpose:
This research will generate information on the presence of emerging contaminants, including chemicals such as pharmaceuticals, in the drinking water of the United States.
Description:
In the past decade, the scientific community and general public have become increasingly aware of the potential for the presence of unregulated, and generally unmonitored contaminants, found at low concentrations (sub-g/L) in surface, ground and drinking water. The most common pathway for the introduction of these chemicals is from an upstream direct discharge of wastewater effluent. In the US, there are more than two dozen communities that draw their drinking water from streams that consist of more than 50 % wastewater during low flow conditions. The US Geological Survey (USGS) and US Environmental Protection Agency (USEPA) have been working on a series of collaborative research projects to determine the identity of chemicals that are commonly present in wastewater effluent, the persistence of these chemicals in surface and ground waters, the removal of these chemicals during drinking water treatment, the formation of by-products during their chlorination and the presence of these chemicals in finished drinking water. In effluents collected at eleven wastewater treatment plants (WWTPs) across the US, 72 out of 110 monitored chemicals were detected at least once, documenting incomplete removal during wastewater treatment. Downstream of the WWTPs, the chemicals exhibited varying environmental persistence. To determine which wastewater chemicals persist through drinking water treatment, a follow-up study examined source and finished waters for nine drinking water treatment plants from across the United States known to be impacted by wastewater. All water samples were analyzed for 84 different emerging contaminants, including 24 pharmaceuticals. The sample collection was designed to account for residence time within the plant in order to match waters before and after treatment. The investigated utilities used varying source waters (surface or ground water), disinfectants (chlorine, chlorine dioxide, chloramine, ozone or UV), and produced different volumes of treated water per day (2.3 to 200 mgd). Thirty-five chemicals were detected at least once, with 28 chemicals detected in the source waters and 23 chemicals detected in the finished waters. The greatest number of chemicals detected in a single source water sample was 15; the greatest number detected in a single finished water was 11. In companion laboratory studies on the effects of chlorination, eight of the 14 chemicals investigated were oxidized by the disinfectant, two of which were at least partially chlorinated. Taken as a whole, these studies demonstrate that to understand the comprehensive environmental impact of emerging contaminants, their persistence, removal efficiencies during waste and drinking water treatment, as well as the potential for by-product formation, must be known.