Master's Culminating Experience
Horizontal subsurface flow constructed wetlands (SSFCWs) are being used worldwide to treat wastewater from a variety of sources. An extensive literature review was conducted to update the current state of scientific knowledge on the performance of SSFCWs for domestic wastewater treatment. This review documented good treatment efficiency for the five commonly measured parameters (TSS, BOD, nitrogen, phosphorus, and fecal coliforms).
An attempt at a Meta analysis turned up a myriad of problems preventing a proper statistical review. These include lack of adherence to standard methods for effluent analysis, varying metrics for reporting treatment efficiency, variability in the nitrogen species which is measured, lack of uniformity of design of the wetlands and on-site systems, and variation in standards required by various agencies and countries. It was not possible to do a Meta-analysis to prove that SSFCWs should be approved technology for onsite wastewater treatment in Ohio.
The author recommends that SSFCWs be approved in Ohio for secondary treatment of home wastewater prior to final treatment by small soil absorption systems. The author recommends that SSFCWs be approved for replacement of failing systems in situations with a high water table or poor soils. A number of other areas need further consideration or research. Ohio Department of Health should serve as a repository for a state-wide database of SSFCWs. USEPA and OEPA should set discharge standards as mass loading based on the volume of effluent discharge, with minimally discharging systems allowed a higher concentration of pollutants than large volume dischargers. USEPA should define what is meant by "failure". Research should be funded to determine the treatment results when iron is used in a SSFCW, to find the ideal design for SSFCWs to assure non-discharge when used for secondary treatment, and to determine the most efficient, economical design for technology export to developing countries. The author recommends that the critical nitrogen species measured should be ammonia N.
Hoddinott, B. C. (2006). Horizontal Subsurface Flow Constructed Wetlands for On-Site Wastewater Treatment. Wright State University, Dayton, Ohio.