New research shows that wastewater treatment plants that employ a combination of purifying techniques followed by reverse osmosis - a process by which water is forced through a barrier that only water can pass - do a good job of removing chemicals that may elicit health effects.
Details were presented today (Aug. 25), at the 228th American Chemical Society meeting in Philadelphia as part of a special symposium on pharmaceuticals and personal care products in the environment.
"As the demand for water continues to increase, especially in arid areas, there's greater pressure placed on an already shrinking water supply," says Joel Pedersen, a University of Wisconsin-Madison environmental chemist, who co-authored a paper detailing this research. "More people are considering the reuse of water."
Wastewater reclamation plants - treatment plants that use additional processes to purify sewage - are already in operation. They produce water to irrigate crops, highway landscaping, golf courses and parks, as well as to be reintroduced into the ground for groundwater recharge, which ultimately could end up in drinking-water supplies.
While this treatment process has the promise to save an evaporating natural resource, Pedersen points out that little is known about just how well water-reclamation plants remove the pharmaceuticals and hormones that typically are found in sewage.
"One concern about water that comes from water-reclamation plants," says the Wisconsin scientist, "is that drugs and hormones in this water aren't removed during the treatment process."
As Pedersen explains, wastewater typically contains any number of pharmaceuticals and hormones that people have either excreted or flushed away for easy disposal. Many times, these chemical compounds remain biologically active, he says, adding that some of them, especially hormones such as estrogen, appear to significantly alter aquatic organisms.
To investigate how well reclamation plants remove potentially harmful drugs and hormones from wastewater, Pedersen and environmental scientists from the University of California Los Angeles tested the water coming out of three Californian treatment plants, two of which produced recycled water used to recharge groundwater. They looked for detectable levels of 19 contaminants, including ibuprofen, caffeine, testosterone, and drugs that lower cholesterol and inhibit seizures.
Pedersen says that the presence of these drugs and hormones in the reused wastewater would be of particular concern if the concentrations were high enough to elicit health and ecological effects. Much work still needs to be done to determine whether low levels found in wastewater are a cause for concern, he adds.
The team of scientists sampled water from all three plants both before and after the water underwent additional treatment processes. While wastewater that had undergone conventional treatment was filtered to remove larger particles, the reclamation plants used additional techniques to remove smaller particles - such as adding lime before filtration or passing water through a microfilter - and then reverse osmosis, a method by which water is forced through a semipermeable membrane that blocks the passage of other molecules.
The research shows that water-reclamation plants employing reverse osmosis do in fact remove more contaminants.
For example, the conventional treatment plant, which after initial treatment still contained detectable levels of 13 of the different contaminants under study, eliminated only five of them from the discharged water. The two reclamation plants, which had 16 and 14 different contaminants present after initial treatment, eliminated 16 and 12 of the chemical compounds, respectively.
"Conventional wastewater treatment processes don't eliminate pharmaceuticals and hormones as effectively, resulting in the release of low levels of these compounds into the environment," says Pedersen. "The more advanced processes, on the other hand, do a pretty good job at removing compounds."
Yet, exactly what these differences in contaminant removal may mean for the environment - and even human health - remains uncertain, says Pedersen.
"This is a case where the analytical chemistry is ahead of the toxicology," he says. "Right now, the ecological effects of chronic low-level exposure to many of these pharmaceuticals are unknown."
- Emily Carlson, 608-262-9772, emilycarlson@wisc.edu
CONTACT: Joel Pedersen, 608-263-4971, joelpedersen@wisc.edu. From Aug. 23-26, Pedersen will be in Philadelphia and can be reached at 608-436-2866. The presentation is located in Loews-Commonwealth B.