Monday, April 22, 2013
For some pharmaceuticals, installing new technologies in wastewater treatment plants might not be enough to protect aquatic ecosystems from the threats they pose. Improved treatment processes would likely mean fewer chemicals could sneak through the plant unchecked. But aquatic plants and animals could still be exposed to dangerous levels of chemicals that commonly enter rivers and lakes by way of city sewers and industrial parks. To effectively block those pharmaceuticals, communities would need to manage or treat water at every point of entry.
This is the conclusion researchers in Sweden reached after spending a year tracking the different ways chemicals enter Lake Geneva's Vidy Bay and simulating the impacts of new treatment techniques. At the heart of their study, published last month in Water Research, is an analytical method that allows researchers to see how materials enter and move within connected ecosystems. The technique, known as substance flow analysis, has been used in the past to understand the spread of heavy metal pollutants and phosphorous. In this study, it was used to get a complete picture of how four pharmaceutical chemicals move between homes, sewers, hospitals, treatment plants, and Vidy Bay.
All of the chemicals tested entered the bay primarily through a regional treatment plant that removes at most a small percentage of the pharmaceuticals in wastewater. Because of this, changes to the way water is treated would reduce the concentrations currently found in the water. Simulations conducted by the researchers showed that ozonation–a treatment process that uses a highly reactive form of oxygen to detoxify chemicals–would be particularly successful at reducing the risk of the four pharmaceuticals tested.
But overflow from flooded city sewers also contributed significantly to the total amount of two of these pharmaceutical pollutants: the antibiotic ciprofloxacin and the anti-epileptic gabapentin. For ciprofloxacin, the discharge from sewers alone was high enough to be a threat to the fish and wildlife that call Vidy Bay home. To effectively protect against this antibiotic, nearby communities would need to install retention pools that can hold excess water during flooding and then redirect it to the regional plant for treatment.
In fact, the risk from ciprofloxacin is great enough that it might also be necessary to treat water from hospitals, where the antibiotic is commonly used, twice–once onsite and then again at a treatment plant. Researchers found that such a two-pronged treatment strategy would reduce the risk ciprofloxacin poses to Vidy Bay by almost 100 percent.
But while it is true in general that numerous strategies may be needed to keep some pharmaceuticals out of local waterways, the specific findings of this study are unique to Vidy Bay and the surrounding communities. Systems flow analysis could be used in other areas to get a map of how pharmaceuticals enter particular waterways, but the findings could not necessarily be generalized to other lakes or rivers.
Chevre, N., Coutu, S., Margot, J., Wynn, H.K., Bader, H.P., Scheidegger, R., and Rossi, L. 2013. Substance flow analysis as a tool for mitigating the impact of pharmaceuticals on the aquatic system. Water Research, 47: 2995-3005. Retrieved from: www.sciencedirect.com/science/article/pii/S0043135413001607