The evaluation of a subsurface-flow constructed wetland for on-site wastewater treatment under the NSF/ANSI Standard 40 protocol design loading.

A subsurface-flow constructed wetland was studied using the National Sanitation Foundation/ American National Standards Institute Standard 40 protocol for Class I on-site wastewater treatment systems at the Baylor Wastewater Research Program (BWRP) site within the Waco Metropolitan Area Regional Sewerage System (WMARSS) treatment plant, Waco, Texas. Raw wastewater from the WMARSS plant was pumped into a two-chambered 1,500 gallon septic tank and flowed by gravity into the 375 ft3 treatment wetland. Both septic tank and wetland effluent samples were analyzed for carbonaceous 5-day biochemical oxygen demand, total suspended solids, and nutrients. In addition, pH values were collected, as well as rainfall and temperature data. The study produced a TSS wetland effluent average of 11 mg/l (96 percent reduction) and CBOD wetland effluent average of 40 mg/l (84 percent reduction). Total nitrogen wetland effluent averaged 30 mg/l (19 percent reduction) and total phosphorus wetland effluent averaged 4.0 mg/l (31 percent reduction).