CONSTRUCTED WETLAND RESEARCH FOR THE TREATMENT OF THE PLANT GORGAS COAL PILE RUNOFF

摘要

Research was conducted to study the transport and fate of inorganic pollutants through a constructed wetland using a Reducing and Alkalinity Producing System (RAPS). RAPS have been used to successfully treat acid mine drainage (AMD). This wetland is designed to treat coal pile runoff, similar to AMD. A primary goal of this research was to evaluate an alternative design that might result in improved pollutant removal. The design was based on the partial re-circulation of treated water into a detention basin, located immediately upstream from the RAPS, containing untreated water. This modification created a semi-passive RAPS-based system we refer to as a Recirculating RAPS (ReRAPS). To test the ReRAPS modification a full-scale RAPS-based wetland capable of recirculation was constructed, operated, and monitored. Factors that may promote improved pretreatment performance in the detention pond during the ReRAPS mode were evaluated using a series of batch tank studies. The wetland monitoring and tank studies have determined that the ReRAPS modification has the potential to enhance the basic RAPS wetland design by moderating the pH of contaminated water and reducing the contaminant loading prior to the RAPS component. The batch tank studies revealed that significant amounts of inorganic contaminants could be precipitated from mixtures of AMD and treated wetland water after 24 hours. Primary factors controlling the removal were pH, initial metal concentration and retention time.