Wetlands May Be Key to Treating Municipal Wastewater

Demands on water resources for municipal, agricultural, and industrial development continue to increase throughout the United States, especially in the arid southwest. In order to meet these demands, wetland habitats are often depleted or destroyed, yet wetlands are important for maintaining and enhancing biodiversity, improving water quality, and protecting watersheds.

To help satisfy the water resource needs of both humans and wildlife, Civil Engineer Jim Sartoris and Aquatic Botanist Joan Thullen from the Fort Collins Science Center have teamed up to investigate the development of wetlands for use in wastewater treatment facilities. "Wetlands are gaining recognition as low-cost, low-maintenance alternatives to some conventional wastewater treatment systems," notes Joan Thullen, "Through our research we hope to demonstrate their effectiveness at providing both reclaimed water for human needs and valuable habitat for wildlife."

One of their projects involves a joint effort between researchers from the Biological Resources Discipline of the U.S. Geological Survey (formerly known as the National Biological Service), Bureau of Reclamation, Arizona Department of Environmental Quality, and the City of Sierra Vista, Arizona. Two 3.5-acre pilot wetlands, which mimic natural emergent wetlands, were constructed in Sierra Vista, Arizona, to test their effectiveness in treating municipal wastewater. Typical wetland vegetation such as bulrush, three-square bulrush, iris, and duckweed were planted in the constructed wetlands. The wetlands have been monitored for two years for their water treatment efficiency and wildlife use.

Preliminary results conclude that the pilot wetlands both improved the quality of the municipal wastewater and provided wildlife habitat. The pilot wetlands met many of the criteria set by the Arizona Department of Environmental Quality for wastewater treatment standards. Levels of ammonium nitrogen, nitrate nitrogen, and total inorganic nitrogen were reduced by at least 80% and total suspended solids and biochemical oxygen demand were reduced an average of 25% and 57%, respectively. In addition, numerous wildlife species, including forty-nine bird species, were observed feeding, resting, breeding and/or nesting at the pilot wetlands.

Early results are promising and the benefits of wetland habitats for the treatment of municipal wastewater continue to be investigated. Studies similar to the one in Arizona are being performed in California, Hawaii, New Mexico, and Nevada. Scientists hope to expand the options for reuse of wastewater treated by wetlands to include not only agricultural uses but also direct surface water recharge into rivers and streams and the irrigation of municipal lands. Future studies will focus on modifying pretreatment procedures and maintaining better control over the flow and retention time of the wastewater in the wetlands.

Wetlands May be Key to Treating Municipal Wastewater