ABSTRACT
Systems that show the best potential for nitrification appear to be either shallow gravel horizontal-flow cells or vertical-flow sand/gravel cells. Shallow horizontal-flow gravel cells are believed to be more effective than deeper cells for nitrification because flow is restricted to the most effective portion of the plant root zone. Pilot-scale, shallow horizontal and vertical-flow cells were installed during the spring of 1991 at Benton, Kentucky, to develop design information for a full-scale constructed wetlands system for nitrification. The cells were dosed with effluent from an operational municipal wastewater constructed wetland. Samples consisted of a grab sample of the influent to the cells and composite and/or grab samples of the effluent from each experimental cell. Effluent concentrations during first few minutes of the cycle were always very low for these cells, but gradually increased during the cycle. The issue is often raised as to the need or benefit of constructed wetlands if one has to utilize another technology for consistent nitrification.
