March 2012, Vol. 24, No.3
Is wastewater treatment transforming pharmaceuticals?
Pharmaceutical compounds may be transformed from nontoxic to toxic forms during wastewater treatment, according to a study conducted by researchers at the University of New South Wales (UNSW; Sydney).
Some drugs can occur in two mirror-image forms known as “enantiomers,” according to a UNSW news release. Chemically similar enantiomers can have extremely different effects on the human body; for example, one may be medically beneficial while the other may be highly toxic, the release says.
UNSW researchers found cases in which beneficial drugs, dispensed as single enantiomers, can transform into the toxic form after interacting with bacteria in wastewater during the treatment process, the release says.
The researchers monitored three pharmaceuticals during wastewater treatment, including the anti-inflammatory drug naproxen, which is manufactured and dispensed as the single enantiomer S-naproxen. Another form of the drug, R-naproxen, is toxic to the human liver and not publicly available, the release says. Researchers observed that some S-naproxen turned into R-naproxen during treatment. This was the first report of enantiomeric inversion during the wastewater treatment process, the release says.
The process mimics a transformation that can occur in the human stomach, where drugs safe in one enatiomeric form can be inverted into a toxic form during metabolism. This occurred with the drug thalidomide, which was administered during the late 1950s to control morning sickness. Thalidomide went through unexpected inversion in the stomach, causing birth defects.
While many studies have reported removal of various pharmaceuticals by wastewater treatment, many assessments have not differentiated between the two enantiomers, the release says. The toxic version of naproxen is not a registered pharmaceutical, so it may not turn up on lists of chemicals requiring assessment, the release says.
Researchers identified the need to refine and optimize assessments to track what treated pharmaceuticals are turning into and make sure this product is not an even greater concern than the original compound, said Stuart Khan, study supervisor and environmental engineer at the UNSW Water Research Centre, in the news release. Khan and his colleagues are working to better understand the mechanism of the inversion process and identify other pharmaceuticals that undergo similar changes during wastewater treatment, the release says.
The study was published in the journal Water Research.
Identifying a connection between caffeine and fecal contamination in waterways
Researchers have identified a correlation between levels of caffeine and the level of bacteria in waterways. A research team led by Sébastien Sauvé of the University of Montreal Department of Chemistry has discovered that traces of caffeine are an indicator of contamination from sewers, according to a university news release.
While Escherichia coli bacteria are used to evaluate the levels of fecal pollution from stormwater discharge, nonhuman sources can contribute to these levels, so the researchers studied the correlation between caffeine and fecal coliform to determine the human contribution to pollution in waterways, the news release says.
The researchers took water samples from local waterways and stormwater sewer outfall pipes and analyzed them for caffeine, fecal coliforms, and carbamazepine, the news release says. Carbamazepine, an antiseizure drug that also is used for various psychiatric treatments, works as an indicator because it degrades very slowly.
Researchers found varying concentrations of all three indicators in all samples. While the scientists did not find a correlation between fecal coliform levels and carbamazepine levels, they did find a modest correlation between fecal coliform levels and caffeine, the news release says. They also found high levels of fecal coliforms but little or no caffeine in some of the samples, which they attributed to urban wildlife, the release says.
“This data reveals that any water sample containing more than the equivalent of ten cups of coffee diluted in an Olympic-size swimming pool is definitely contaminated with fecal coliforms,” Sauvé said in the news release. “A caffeine sampling program would be relatively easy to implement and might provide a useful tool to identify sanitary contamination sources and help reduce surface water contamination within an urban watershed.”
Researchers expand on benefits of long solids retention time
Long solids retention times (SRTs) offer three major benefits in addition to the typical use for nitrification, according to an article in the January issue of Water Environment Research (WER).
These additional benefits include increased oxygen-transfer efficiency, improved biomass particle-size distribution, and enhanced removal of many emerging contaminants. Improved particle-size distribution results in more-efficient clarification with fewer effluent particles and suspended solids. Long SRTs also can remove greater quantities of pharmaceuticals, personal care products, and endocrine-disrupting compounds, the article’s abstract says.
The article presents experimental results from several treatment plants where oxygen-transfer efficiency and particle size increased with longer SRT. The results also show evidence documenting improved removal of emerging contaminants and biodegradable organic carbon, the abstract says.
“A long-term survey of three treatment plants concludes that operating at higher SRT is not as energy intensive as typically assumed,” the abstract says.
The article, “Toward Long Solids Retention Time of Activated Sludge Processes: Benefits in Energy Saving, Effluent Quality, and Stability,” appears in the January issue of WER and can be downloaded free at bit.ly/xRgeuq.
|Water Environment Research allows open access to one article per issue on a range of important technical issues such as nutrient removal, stormwater, and biosolids recycling. Find more open-access articles at www.ingentaconnect.com/content/wef/wer.
© 2012 Water Environment Federation. All rights reserved.