Constructed Wetlands: A Low-cost Alternative

Constructed wetlands are finding increasing uses communities because they cost less than conventional wastewater treatment plants. Also they readily can be accommodated in these areas, which have the land such systems require. However, urban areas also are expressing a growing interest. In Arizona, there is Tucson's Sweetwater facility. Also the pilot project at Phoenix's Tres Rios facility is the possible precursor to a full-scale facility.

Constructed wetlands are useful for treating municipal effluents, industrial and commercial wastewaters, agricultural runoff, stormwater runoff, animal wastes, acid mine drainage, and landfill leachates. They use wetlands' plants, soils, and their associated microorganisms to remove contaminants from wastewater by mimicking the processes in natural wetland ecosystems.

The town of Jerome, AZ, recently chose to construct a wetland rather than build a mechanical treatment plant to treat its wastewater. Maintenance of the mechanical treatment plant was to cost about U.S.$1000 per month, whereas maintaining the wetland was expected to cost "little or nothing." Also in Arizona is a jointly constructed-wetland project by the City of Sierra Vista and the U.S. Bureau of Reclamation. It is expected to demonstrate the technology's environmental benefits. Such benefits would derive from using treated wastewater for aquifer recharge and for release directly to the river.

More research is taking place to understand constructed wetlands' workings. The Constructed Ecosystems Research Facility is devoted to wetland research. CERF provides a setting to evaluate the effectiveness of a constructed wetland's facility in an arid land climate. It is sponsored by the Pima County Wastewater Management Department, with research conducted by the University of Arizona's Office of Arid Lands Studies.

Also the University of Arizona, the Natural Resources Conservation Service, and Glendale's Rovey Dairy are working together on a
constructed-wetland project that treats the dairy's wastewater.

Constructed wetlands are recent to Arizona. Regulatory agencies thus generally regard them as non-traditional. The state, therefore, has undertaken efforts to adopt appropriate constructed wetland regulations. A
total-quality-improvement team, organized by the Department of Environmental Quality, is identifying issues that inhibit wetland construction in Arizona. It also is working on solutions to regulatory and technical concerns.

The previous case study is adapted from a report by the Water Resources Research Center at the University of Arizona.