Nitrate removal for Platte valley, Nebraska synthetic groundwater using a constructed wetland model

The purposes of this study were i) to show that nitrate removal by denitrification from Platte Valley, Nebraska synthetic groundwater was possible utilizing a model, laboratory-scale, constructed wetland (MW) and ii) to evaluate the MW's influence on water quality when the hydraulic retention time (HRT) was varied. Denitrification was successfully achieved using a starch and cellulose mixture as the carbon source, instead of carbon from plant growth, and a 30 mg l(-1) nitrate-nitrogen synthetic feed concentration. For 1, 3, and 7 day HRTs, the MW achieved nitrate-nitrogen plus nitrite;nitrogen (nitrate/nitrite-nitrogen) removals of 82%, 98%, and 88%, respectively. The effluent nitrate/nitrite-nitrogen levels were not significantly different, based on their 95% confidence intervals. For all HRTs, average effluent organic-nitrogen concentrations were less than 2.0 mg l(-1) and average effluent ammonia-nitrogen values were less than 0.5 mg l(-1). For 356 mg l(-1) chemical oxygen demand (COD) addition to the MW, the MW achieved COD removals of 84%, 89%, and 98% for the 1, 3, and 7 day HRTs, respectively. Volatile fatty acid effluent levels were below the detection limit. Residual organic matter in the treated water may make further treatment necessary.