Biological nitrogen removal using a vertically moving biofilm system

In this study, a biological nitrogen removal process using a vertically moving biofilm system was used to treat synthetic wastewater. The process consisted of two pre-denitrification units, one combined carbonaceous removal/nitrification unit and three nitrification units. Each unit employed biofilm growth on a plastic module. In the anoxic units, the modules were vertically moved, while always submerged, in the bulk fluid; in the aerobic units, they were moved vertically up into the air and down into the wastewater. Three small-scale experiments, having different recirculation ratios and influent loadings, were conducted at a controlled temperature of 11 °C. In this system, the carbonaceous removal efficiency was in the range of 94–96% and the total nitrogen removal efficiency was 77–82%. In the anoxic units, the denitrification efficiency was 94–98% and the areal denitrification rates, based on the surface area of the biofilm modules, were 2.9–3.8 g NO3-N/(m2 • d). The nitrification efficiency occurring in the aerobic tanks was up to 95% and the maximum areal ammonium removal rates were 1.3–1.8 g NH4-N/(m2 • d).