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Improving the Quality of Wastewater To Tackle Trace Organic Contaminants: Think before You Act! Andrew C. Johnson*,† and John P. Sumpter‡ †
Centre for Ecology and Hydrology, Wallingford, Oxfordshire OX10 8BB, U.K. Institute for the Environment, Brunel University, Uxbridge, UB8 3PH, U.K. the benefits that would accrue from a massive investment in upgraded sewage treatment. For better or worse, sewage effluent is likely to be a major driver of river biodiversity and the local ecosystem. In developed Western Countries, the problems of high organic loadings causing oxygen depletion or high toxic ammonia levels have largely been dealt with. Thus, we now have a lowland river ecosystem that is likely to be well adapted to this environment. Most of the so-called emerging contaminants (like EE2) actually emerged over 40 years ago. Nevertheless we are now aware of the signals of endocrine disruption in wild fish closely linked with sewage effluent. These raise legitimate concerns over the future of fish populations due to reproductive failure. Yet we are not aware of stories of fish populations in decline in lowland rivers related to sewage effluent. This might be because we have not looked properly, although we have recreational anglers to help us. They are often the first to raise an alarm, such as when improved sewage treatment was linked to changes in fish species composition.3 Many macroinvertebrates are sensitive to chemicals, and a reduction in species diversity has been linked to effluent (although it is unclear whether this was low DO, salinity or organic chemicals). Yet a survey of species richness trends of invertebrates in UK rivers from 1991 to 2008 found BACKGROUND this had steadily improved, even in the most urbanised river There is increasing urgency about the need to improve the reaches.4 In Germany, it has been reported that bream in a performance of sewage (wastewater) treatment in order to number of rivers, including the Rhine, have been continuously eliminate polar organics from domestic sources that we know, improving in terms of average weight, length, and condition or fear, are harming wildlife. The issue is taken so seriously that factor over the past 20 years.5 the Swiss Federal Government is planning to introduce ‡
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sophisticated tertiary treatment to many of its sewage treatment plants (STPs) to eliminate these worrisome contaminants. Based on current knowledge, most of the proposed techniques would appear to be very expensive to build and maintain. A recent proposal to add 17a-ethinylestradiol (EE2), 17bestradiol (E2) and diclofenac to the WFD list of priority substances in the European Community (COM(2011)876) is a dramatic example of the concern generated by some pharmaceuticals. Reducing concentrations of these pharmaceuticals (particularly EE2) would require the STPs along 25− 30% of Europe’s rivers by length to receive tertiary treatment technology.1 Such efforts and costs would be very daunting. For the UK a cost of £31 billion is predicted, but a recent article states “without question, ecological quality. . .will benef it from f urther upgrades or implementation of state of the art treatment technologies”.2 However, we believe the issue requires further critical examination before action is taken.
COULD THERE BE UNINTENDED CONSEQUENCES ASSOCIATED WITH WASTEWATER TREATMENT UPGRADES? The argument is that improving sewage effluent with advanced technology would be a “no regret” decision.2 To remove trace organics, a range of tertiary treatment options are available. But advanced oxidation approaches to treatment are known to cause, at least in some cases, small and highly mobile breakdown products which are a lot less benign then the originals, such as NDMA. Treatments such as nanofiltration and activated charcoal could remove 99% of the organic molecules in effluent. It is likely that most of these technologies would require considerable additional energy requirements, thus potentially increasing our societal carbon emissions, something that responsible societies should be trying to reduce. A challenging question to ask is how might the lowland river ecosystem, that has adapted to sewage effluent over the past 40
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WHAT IS THE PROBLEM EXACTLY? In the real world of limited resources and political pressures, scientists must define the problems that would be avoided and © XXXX American Chemical Society
Received: February 20, 2015
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DOI: 10.1021/acs.est.5b00916 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
Viewpoint
Environmental Science & Technology
(4) Vaughan, I. P.; Ormerod, S. J. Large-scale, long-term trends in British river macroinvertebrates. Global Change Biol. 2012, 18 (7), 2184−2194. (5) Teubner, D.; Paulus, M.; Veith, M.; Klein, R. Biometric parameters of the bream (Abramis brama) as indicators for longterm changes in fish health and environmental quality-data from the German ESB. Environ. Sci. Pollut. Res. 2015, 22, 1620−1627.
years, change if organic chemical emissions to water were eliminated? It seems plausible that fish species now abundant in lowland rivers containing effluent, such as roach, bream, and stickleback, have benefitted from the current level of organic discharge. Presumably this organic discharge helps sustain detritus and periphyton which have become an important part of their diet. This loss might cause some of these cyprinid fish populations to come under pressure. Perhaps for many lowland fish there is an ideal level of supplemental organic supply from effluent; too much causes oxygen sag and asphyxiation, while too little would leave them weak and undernourished. Thus, we might find ourselves in the absurd situation of damaging the very fish populations we were trying to protect by improving sewage effluent quality!
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HONESTY THEN ACTION Ideally, removal treatments would emerge that precisely targeted the compounds of concern, such as EE2. But it is hard to imagine exquisitely specific removal techniques dealing with millions of metric tons of wastewater per day. This leaves us with the broad spectrum approaches that would largely eliminate all the organics in effluent. Before the adoption of such high-energy organic removal technologies on a wide scale, we recommend the following criteria be addressed: • Provide the evidence that wildlife populations are declining due to exposure to chemicals in domestic effluent. • Identify which species would decline if we switched off the tap of organics in effluent. • Publish both the national costs to the taxpayer and energy demands. If the increase of carbon emissions were to be significant, this should be stated. • Reveal probable ecosystem changes to all stakeholders (particularly anglers) and engage them in the cost-benefit analysis that must follow. Many people invoke the “precautionary principle”, but this should only be applied if we are certain that the changes we insist on do not themselves cause more harm to the wildlife we currently possess. An environmental scientist’s duties do not end with the call for substances to be controlled.
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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REFERENCES
(1) Johnson, A. C.; Dumont, E.; Williams, R. J.; Oldenkamp, R.; Cisowska, I.; Sumpter, J. P. Do concentrations of ethinylestradiol, estradiol and diclofenac in European rivers exceed proposed EU environmental quality standards? Environ. Sci. Technol. 2013, 47, 12297−12304. (2) Oehlmann, J.; Schulte-Oehlmann, U.; Prasse, C.; Ternes, T. Chemical and ecotoxicological characterization of wastewater treatment plant effluents. What are the challenges and prospects? An academic perspective. Environ. Toxicol. Chem. 2014, 33 (11), 2408− 2410. (3) Cowx, I. G.; Broughton, N. M. Changes in the species composition of anglers catches in the River Trent (England) between 1969 and 1984. J. Fish Biol. 1986, 28 (5), 625−636. B
DOI: 10.1021/acs.est.5b00916 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
