ASU Research E-Magazine: Wastewater to Wetland

To the untrained eye, it looks like a swamp in the desert. Roland Wass sees it as the future of wastewater treatment.

Wass is a doctoral student at ASU and project manager for the Tres Rios Demonstration Project. The project is designed to study the use of wetlands as areas in which to treat household wastewater. Scientists define a wetland as being a large swampy or marshy environment with lots of vegetation. Many animals and insects also depend on these habitats.

Tres Rios is an 11-acre wetland that actually is a part of the Phoenix municipal wastewater treatment plant located on 91st Avenue.

Wass works with ASU’s Peter Fox, an associate professor of civil and environmental engineering. They are trying to demonstrate the use of bacteria in the wetland as a means to provide advanced treatment for household wastewater.

Wastewater includes basic household waste coming from sinks, toilets, or washing machines. Once down the drain, wastewater makes its way through a maze of pipes and sewer lines to a water treatment plant. These facilities use processes that are designed to remove potentially harmful or toxic particles from the water. Once cleansed, the water can be used again by agriculture, industry, or for habitat enhancement.

There is a catch. The Environmental Protection Agency currently is strengthening permit requirements to improve the quality of water released by treatment facilities. New treatment processes are needed.

This is where Wass wants to add wetlands to the formula.

The 91st Avenue facility treats almost 2 million gallons of Phoenix area wastewater every day. Wass and Fox take a portion of that water and funnel it into a densely vegetated pond. The pond appears to be stagnant. But it actually is flowing at a slow pace. As the pond water flows, bacteria attack and break down the harmful particles and toxins.

“The water is cleaned up by the bacteria and by physical processes such as settling,” Wass says. “Bacteria either consume the pollutants or transform them into harmless compounds.”

The water might be left in the wetland system anywhere from three to 15 days, depending on particular water quality requirements. Throughout the process, Wass monitors the water condition and the environment being created. After the water flows through Tres Rios, it is channeled into the Salt River, where it is used by the Buckeye Irrigation District to water crops.

The project is the joint property of the cities of Glendale, Mesa, Phoenix, Scottsdale, and Tempe. If the results are what Wass hopes they will be, the project will be expanded by 400 to 800 acres. The wetland will then handle 150 million gallons of water per day. Scientists are currently conducting a feasibility study. The final project could be ready for construction by 2003.

Wass is taking a particular look at the net environmental impact of the project. All of the water and vegetation make good habitat for area wildlife.

Tres Rios is the new home to egrets, herons, and osprey. The wetland is routinely visited by muskrats, beavers, coyotes, and other small animals.

The major concern of the researchers is to make sure the area is a safe habitat for all creatures, including humans who live in the surrounding area.—Gary Campbell