Constructed wetlands represent a growth industry, as such facilities are increasingly being used both in Arizona and throughout the nation. In 1990, Arizona only had four constructed wetlands treating municipal wastewater. Today 26 municipal and onsite constructed wetlands are now operating in the state, with at least 24 others either awaiting approval or under construction.

(Constructed wetlands, a technology designed to mimic processes found in natural wetland ecosystems, utilize wetland plants, soils and their associated microorganisms to remove contaminants from wastewater.)

Kris Randall, unit manager for the Arizona Department of Environmental Quality's Municipal Wastewater and Recharge Unit, notes that constructed wetlands especially appeal to rural communities because they cost less than conventional wastewater treatment plants, and these areas have the land such systems require. "Because of those two factors we see rural communities looking at constructed wetlands as their mode of treatment," says Randall.

For example, the town of Jerome recently chose to construct a wetlands to treat its wastewater rather than a mechanical treatment plant. Maintenance of the mechanical treatment plant was to cost about $1,000 per month while the cost to maintain the wetland is expected to be "little or nothing." Construction is scheduled to begin this summer.

Also, the city of Sierra Vista, along with the U.S. Bureau of Reclamation, is planning a constructed wetland. This project could demonstrate how constructed wetlands can provide environmental benefits. Options for using its treated wastewater include aquifer recharge, to lessen the effect groundwater pumping has on the San Pedro River, and also releasing the treated water directly into the river.

Urban areas also are expressing a growing interest in the potential of constructed wetlands. Kingman's constructed wetland facility began operation in 1994. Thatcher intends to initiate a facility, and Nogales is considering a pilot project. Tucson's Sweetwater facility is expected to be completed by the end of summer or early autumn, and Phoenix's Tres Rios facility is a pilot project to study the possibility of building a full-scale wetland facility.

Along with increased use of constructed wetlands to treat wastewater, more research is taking place to understand its workings. For example, the Constructed Ecosystems Research Facility is a wetlands project devoted to research. Sponsored by the Pima County Wastewater Management Department, with research conducted by the University of Arizona's Office of Arid Lands Studies, CERF provides researchers a setting in which to evaluate the effectiveness of a constructed wetlands facility in an arid land climate.

Also research is an important component in a recent project funded by the Arizona Department of Water Resources. The University of Arizona, the Natural Resources Conservation Service and the Rovey Dairy in Glendale are working together on a constructed wetland project to treat the dairy's wastewater. The project serves a dual purpose, to provide an operating dairy with a working wastewater treatment system and to allow researchers an opportunity to study the workings of a wetland system.

Constructed wetlands are sufficiently recent to Arizona that regulatory agencies generally regard them as non-traditional. "These systems are typically used as part of the treatment train," Randall said.

Efforts are underway to adopt appropriate constructed wetland regulations. ADEQ officials organized a Total Quality Improvement team to identify issues inhibiting wetland construction in Arizona and to recommend solutions to regulatory and technical concerns. ADEQ is in the process of reviewing current agency practices to better incorporate TYI recommendations, Randall said.

Constructed wetlands have varied treatment capabilities and can remove contaminants from various kinds of water. Constructed wetlands are used to treat municipal effluents, industrial and commercial wastewaters, agricultural runoff, stormwater runoff, animal wastes, acid mine drainage and landfill leachates.

A topic of growing interest, constructed wetlands will be the featured topic in the next Arroyo, to be published in April. Arroyo is a publication of the Water Resources Research Center at the University of Arizona.