Clemson Study: Commercial Aquatic Plants Can Treat Wastewater

Nursery and greenhouse operations depend on the use of fertilizers, growth regulators, insecticides, and fungicides. Growers also rely on the use of soilless media, or substrate, in the production of container crops. Concerns arise when excessive irrigation of the container crops grown in soilless media leads to leaching and loss of nutrients and chemicals in runoff. The resulting runoff can escape from production areas and have a negative impact on surface and ground water.

Constructed wetlands (CWs) have been promoted as inexpensive, low-technology approaches to treating agricultural, industrial, and municipal wastewater to comply with increasingly stringent environmental regulations. CWs, or marshes built to treat contaminated water, incorporate soil and drainage materials, water, plants, and microorganisms. "Surface-flow" constructed wetlands resemble shallow freshwater marshes and generally require a large land area for wastewater treatment. More effective for greenhouse and nursery operations with limited production space and expensive land are a type of constructed wetland called "subsurface flow." These wetlands consist of a lined or impermeable basin filled with a coarse medium, typically gravel, and wetland plants. Wastewater flows horizontally or vertically below the surface of the media to prevent exposure to humans or wildlife.

According to a Sept. 28 press release, Robert Polomski and his colleagues at Clemson University published a study in the June 2008 issue of HortScience that investigated the nitrogen and phosphorus removal potential by a vegetated, laboratory-scale subsurface flow system.

"In this study, we investigated a cost-effective approach of reducing water treatment costs. Instead of traditional wetland plants, we found that commercially available aquatic garden plants can be used in a production/remediation system."

Over an eight-week period, five commercially available aquatic garden plants received a range of nitrogen and phosphorus that spanned the rates detected in nursery runoff.

According to Polomski, "the results support the use of aquatic garden plants as aesthetic and economically viable alternatives to traditional wetland plants in constructed wetlands. Although more research is necessary to address other variables, the study concluded that the use of commercially produced plants in constructed wetlands has the potential to generate revenue for producers.

For the complete study, visit http://hortsci.ashspublications.org/cgi/content/abstract/43/3/868.

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