Nitrate removal in wetland microcosms

The effect of hydraulic loading rate (HLR; 5 to 20 cm day(-1)) and carbon addition(1-6 g dried plant material per week) was determined at two temperatures (28 degrees C and 35 degrees C) in 18 flow-through sediment-water wetland microcosms that were fed nitrate-contaminated water (30 mg N L-1). Nitrate removal efficiencies varied from 8% to >95%, decreasing with increasing HLRs and increasing with increasing carbon addition rates. The effect of HLR, and carbon addition rate were integrated into the C:N ratio, which alone was highly predictive of nitrate removal efficiency. As nitrate removal efficiencies increased, dissolved organic carbon in the effluent also increased, as did chloroform formation potential. Nitrate-treatment wetlands may be a feasible method of remediating nitrate-contaminated groundwater. (C) 1998 Elsevier Science Ltd. All rights reserved.