Effect of wastewater step-feeding on a DHS reactor treating nitrogen rich wastewater

Abstract

 In this study, DHS (Down-flow Hanging Sponge) reactor was used for partial nitrification of ammonium rich actual wastewater. To prevent pH decrease with nitrification, step-feeding was applied to DHS reactor and evaluated its effect on partial nitrification. The conventional one point feeding, 2 step feeding, and 4 step feeding were applied under constant nitrogen volumetric loading. Under the one point and 2 point feeding condition, about 40% of ammonium was oxidized and effluent pH was decreased to around 6.0. But for 4 step feeding condition, the pH was maintained around 7.5 despite the about 50% of ammonium was oxidized. Retained sludge of the DHS reactor had 26~49 mg-N/g-VSS/day of denitrification activity on day 516. From the profile of denitrification activity, step-feeding could be enhance the denitrification not only prevention of the pH decrease.