SUD Hears Report on Pilot Constructed Wetland Proposal

by Leslie Lytle, Messenger Staff Writer

In lieu of the regular monthly business meeting, the Board of Commissioners of the Sewanee Utility District of Franklin and Marion Counties met with students of University of the South biology professor Deborah McGrath to review their research into the feasibility of a pilot constructed wetlands as a means of recycling wastewater.

 University of the South students collaborated with student researchers from the University of Georgia to conduct the study. In Georgia, constructed wetlands are used to treat wastewater at 20 facilities. In China, where the method has been in use for more than 1,000 years, there are more than 6,000 constructed wetlands. At the present, there is only one constructed wetlands water treatment facility in Tennessee.

The students distinguished between required monitoring (dictated by government regulations) and the information that could be gleaned from additional monitoring in a constructed wetlands. Regulations require monitoring of nitrate, E. coli bacteria and dissolved oxygen, which is necessary to break down organic material. Regulations do not require monitoring for pharmaceuticals, PCBs, heavy metals and pesticides, which wetlands have been shown effective in removing, although at different levels. A pilot wetlands would allow for comparisons to SUD’s wastewater treatment facility, which employs spray fields and standard sewage treatment like that in Winchester.

The students also researched the income potential of constructed wetlands. Plant growth in a wetlands needs to be periodically burned or harvested. Burning costs money and leaves residual nutrients in the form of ash. Harvested biomass can be used for compost, converted to biomass fuel pellets or converted to biogas with a biodigestor. The students suggested the most feasible and potentially profitable method for Sewanee would be integrating the harvested biomass into the University’s extant composting program. The two biomass pellet facilities in Tennessee are too far away to be practical for a pilot program, and biodigestors are costly.

The student researchers noted that although plant growth in the wetlands aided in the removal of undesirable nutrients, bacteria and microbes attached to the plants were the primary vehicles of nitrate reduction.

In interviews with University students and faculty, the students found an “overall openness and acceptance of recycled wastewater for drinking water.” Preliminary to surveying the non-University community, the students presented the SUD board with sample questions to review and invited their input.

The student researchers pointed out that in addition to providing a source of safe, clean drinking water, the ponds and vegetation in a constructed wetlands attracted wildlife, increasing biodiversity. They emphasized the importance of community outreach geared to erasing the perception of recycled wastewater as dirty and fostering appreciation of the benefits wetlands offered, both for recreation and as outdoor laboratories. 

To aid in educating the public, the students created a short video on the functioning and benefits of constructed wetlands. The video discussed the drought of 2007, when nearby Monteagle ran out of water, Sewanee was down to a 35–40 day supply and metropolitan areas like Atlanta, Ga., were under severe water restrictions. The areas in Georgia served by constructed wetlands suffered no water shortage and sold water to other utilities.

Because Sewanee is at the top of the watershed, it provides an excellent opportunity for examining the effectiveness of wetlands in removing substances not typically tested for, such as pharmaceuticals and heavy metals, McGrath said.

In the film, SUD manager Ben Beavers stressed that if SUD were to construct a pilot wetlands, the water to be used for drinking water “must be as good or better than the water from the watershed.”