USING WETLANDS TO IMPROVE WATER QUALITY IN OHIO: EXPECTATIONS AND REALITY

Poor performance of constructed wetlands in Ohio for treating domestic waste and acid mine drainage indicates that these systems must be totally redesigned or rejected as an alternative for improving water quality. Analyses of water quality data for 21 domestic wastewater and 8 acid mine drainage wetlands indicate that while these systems may improve water quality as expected, they often fail to meet acceptable effluent guidelines. Single-family domestic wastewater treatment systems in Ohio share a common 3-cell design (septic tank and 2 treatment wetlands). Inlet, intermediate cell and outlet loads (fecal coliform, total suspended solids, biochemical oxygen demand, ammonia, dissolved oxygen, total phosphorus and nitrate) for a group of 9 of these systems in western Ohio were monitored from 1995 - 2001. The data display large variances with overall load reductions found to be consistent with similar systems elsewhere in the world. However, these systems collectively fail to meet proposed National Pollutant Discharge Elimination System (NPDES) effluent guidelines in 75 percent of the samples. Similar data for a group of 11 systems from northern Ohio display less variance and overall higher treatment efficiencies, but still fail to meet proposed NPDES standards in 40 percent of the samples. With the exception of ammonia and phosphorus, no systematic design trends appear to contribute to failure in these systems. Acid mine drainage in Ohio is treated using several multi-cell designs. The variability in loads, designs and treatment performance these systems limits generalizations concerning specific designs. Individual systems data display large variability when analyzed for cell-to-cell changes in Fe, Mn, Ca, Na, K, Mg, Si, Al, Cl, and OH. Iron load reductions are consistently high while other pollutants display much lower load reductions or even remobilizations. Lack of routine maintenance is found as a major contributing factor to system failures.