Downstream Discharge

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Science  01 Feb 2013:
Vol. 339, Issue 6119, pp. 490
DOI: 10.1126/science.339.6119.490-c

Wastewater has the potential to serve as a renewable source of energy, nutrients, and clean water. However, most wastewater is treated minimally to remove pathogens and organic matter and released into the environment. In highly urbanized, developed areas, a single river may receive discharged effluent from several wastewater treatment plants, so that a sizable fraction of the downstream water is recycled wastewater. By studying two rivers in and around Chicago, Drury et al. showed that although wastewater effluent released into rivers may meet water quality standards, it can have an impact on downstream ecosystems. Discharged effluent resulted in increased nutrients such as nitrate and phosphate in the water column and, perhaps surprisingly, decreased sediment organic matter. The downstream sediments showed decreased bacterial abundance and diversity, shifting from communities that included sulfate-reducing bacteria to communities dominated by nitrate-oxidizing bacteria. Although the two rivers have very different biological and chemical properties upstream of the wastewater treatment plants, they were homogenized to the point where they were nearly indistinguishable downstream.

Appl. Environ. Microbiol. 10.1128/AEM.03527-12 (2013).

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