Designing Wetlands to Remove Drugs and Chemical Pollutants

*Note: I thought this was some great information about cleaning up drinking water in an environmentally friendly way.

Drinking water supplies around the world often contain trace amounts of pharmaceuticals and synthetic compounds that may be harmful to human health. One solution being tried in the U.S. and Europe is to construct man-made wetlands that naturally degrade these contaminants.

by carina storrs

Rising high in the San Bernardino Mountains in Southern California, the Santa Ana River flows westward through cities and towns with a total population of nearly 5 million. Along the way, it receives so much sewage that 90 percent of its flow during the dry summer season is effluent, whichis cleaned again and again at several dozen wastewater treatment plants.

Near the end of its 96-mile course, the Santa Ana comes to a seeming standstill in thePrado Wetlands. Covering 425 acres, the wetlands site — designed by engineers — consists of a series of rectangular ponds, through which the river's gentle flow is controlled by dam-like weir boxes. It takes about a week for water to traverse the wetlands, during which time cattails and other vegetation help remove nitrogen, phosphorous, and other contaminants.

Today, the Prado Wetlands, which are operated by the Orange County Water District, are part of a new project to remove a different kind of pollution: the residues of medical drugs and synthetic organic compounds, such as herbicides, that are found in small concentrations in rivers but thatmayaffect endocrine activity, metabolism, and development in humans. A year-old pilot project at the Prado Wetlands channels river water through three ponds, each about the length of five Olympic swimming pools. Sunlight and bacteria degrade residues of antibiotics, anti-inflammatories, sex hormones, and other drugs and man-made chemicals before the Santa Ana reaches Anaheim, 20 miles downstream. There the river provides the drinking water for 2.5 million people in northern Orange County.

Concern has risen about the potential danger that may come from drinking water tainted bysmall concentrations of pharmaceuticalsthat pass through our bodies and are flushed down the toilet, not to mention other synthetic compounds discharged by agriculture and industry. Research has shown that endocrine disruptors and antidepressants may harm reproduction in fish, and endocrine-disrupting compounds also have been linked toadverse health effects in humans. Scientists also fear that the persistence of antibiotics in the environment could promote the development of antibiotic-resistant bacteria.

Currently, there are no U.S. regulations for medical drugs under the Safe Drinking Water Act, and only a few for the residues from consumer products. However, the U.S. Environmental Protection Agency'sContaminant Candidate List, which establishes what chemicals should be evaluated for possible regulation, in 2009 included several endocrine disruptors called estradiols, found in products such as birth control pills. The list also included erythromycin, an antibiotic. The European Commission placed two types of estradiols and a painkiller called diclofenac on a similar watch list in 2013.

As a result of growing concerns, scientists and government authorities in the U.S., Europe, and elsewhere are experimenting with the use of so-called "constructed wetlands" to remove these pharmaceuticals and chemicals from effluent released by wastewater treatment plants. Constructed wetlands have been used for several decades in the United States and Europe to remove nitrogen and other traditional pollutants from wastewater. In the U.S., roughly 250 constructed wetlands have been built to treat effluent from wastewater treatment plants, and in Europe thousands of constructed wetlands exist, mainly for treating wastewater from smaller communities.

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