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Wastewater Indicators Shown to Degrade in Streams

USGS scientist measuring pH and other water properties on the banks of Fourmile Creek, Iowa
USGS scientist measuring pH and other water properties on the banks of Fourmile Creek, Iowa, before collecting a sediment sample for laboratory biodegradation experiments.

In a recent paper published in Environmental Toxicology and Chemistry U.S. Geological Survey (USGS) scientists reported results of a study that examined the biotransformation of three emerging contaminants that are potential wastewater indicators—caffeine, nicotine, and cotinine (a byproduct of the metabolism of nicotine in humans). The scientists simulated stream conditions in their laboratory by placing a mixture of stream sediments, stream water, and contaminants in bottles (microcosms) under different chemical conditions (for example with and without oxygen). Their results showed that microorganisms are able to selectively degrade these three compounds efficiently in the presence of oxygen and to a lesser extent in the absence of oxygen.

USGS scientists are investigating whether certain chemicals found in the wastewater discharged from sewage treatment plants can be use as indicators of wastewater contamination in rivers and streams (see Tracing Wastewater - Using Unique Compounds to Identify Sources of Contamination for more information). Using these unique compounds, commonly referred to as emerging contaminants, as indicators of human wastewaters requires an understanding of how stable they are in the environment. Little is known about the potential of many emerging contaminants to be transformed or degraded to other chemicals by microorganisms in streams; a process known as biotransformation.

The potential degradation of these compounds needs to be considered by water-resource managers if they are to be used as wastewater indicators.  The detection of these compounds in streams provides compelling evidence of an upstream source of wastewater; however, their absence could be a result of either the absence of wastewater or biotransformation.

Glass serum vials used to construct microcosms for laboratory biodegradation experiments
Glass serum vials (bottles in the foreground and in the box) are used to construct microcosms for laboratory biodegradation experiments. The syringe is use for injecting chemicals for testing and withdrawing samples for analysis. Radioactive labeled chemicals (vial on right) are used so reaction products can be identified.

Reference

Bradley, P.M., Barber, L.B., Kolpin, D.W., McMahon, P.B., and Chapelle, F.H., 2007, Biotransformation of caffeine, cotinine, and nicotine in stream sediments--Implications for use as wastewater indicators: Environmental Toxicology and Chemistry, v. 26, no. 6, p. 1116-1121, doi:10.1897/06-483R.1.

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