Monday, February 11, 2013
The drive to more efficiently and effectively remove pharmaceutical chemicals through wastewater treatment is at the heart of a lot of scientific research. Medicines have been found in rivers, groundwater, and the drinking water of millions of Americans. And common wastewater treatment methods, such as activated sludge, have proven to be only partially effective when it comes to removing these chemicals. In fact, one study in the United Kingdom found that wastewater treatment only removes between 70-85 percent of pharmaceuticals before pumping water back into nearby waterways.
Researchers have responded with a flood of studies examining different ways to improve the removal of pharmaceuticals. Approaches to this problem are very diverse. Some studies look for ways to improve currently technologies, some test new treatment methods, and still others look at how pharmaceuticals degrade naturally in different environments to learn how best to tackle them in artificial treatments. Some results stay in the lab–providing necessary information on what happens to contaminants under different treatment scenarios–but some results can translate directly into real-world practices.
One of these studies, published last year in the Journal of Environmental Quality, targeted a specific antibiotic. Sulfamethazine is an antibiotic commonly added to livestock feed to prevent disease in cattle and pigs. Because this chemical is slow to break down, it can persist in manure for up to a year and is easily carried in stormwater runoff into rivers and streams. Standard wastewater treatment methods are costly and only partially effective when used to remove this antibiotic, but the synthetic resins analyzed in this study filtered out as much as 99.75 percent by trapping the antibiotic molecules as the water moved through them. And since these resins can be cleaned with hot water or organic solvents and reused over 2,000 times, this technology could be both an economically and environmentally friendly way of removing sulfamethazine from water supplies.
In contrast, a 2012 study out of Europe examined ways to improve a commonly used treatment process: chemical oxidation. The most common oxidant used in this process to convert contaminants into harmless compounds is ozone, which can be expensive and difficult to manage. Some of the oxidants tested proved ineffective at removing the six pharmaceuticals added to the test water. The study did reveal, though, that chlorine dioxide could be used as an alternative to ozone in plants where the chemical could be added right before the water is returned to surrounding waterways. For smaller treatment plants especially, chlorine dioxide could be a cheaper and easier way to make water safe for the environment, animals, and humans.
To go behind the scenes on wastewater treatment research, read this UpClose interview with Dr. Timothy Strathmann.
Written by: Anjanette Riley, IISG Science Writer