RETROFIT OF BIOLOGICAL NUTRIENT REMOVAL PROCESS ASSISTED BY NUMERICAL-SIMULATION WITH ACTIVATED-SLUDGE MODEL NO-2

In existing wastewater treatment plants that employ biological nitroge n and phosphorus removal processes, a low concentration of organic sub strates in the influent wastewater has a destabilizing effect on the p hosphorus removal process. Many efforts have been made to combat this problem, including reconstructing the process flow and improving opera tion and control systems. However, because the mechanism used for biol ogical phosphorus removal is complex, it is difficult to establish eff ective empirical methods. For this paper, we constructed a simulator f or the wastewater treatment process and tried to improve on current pr ocedures, focusing on the planning, execution, and evaluation of metho ds of retrofitting existing WWTP with equipment for biological nutrien t removal. The Shinnanyo WWTP uses the anaerobic/aerobic activated slu dge process to remove nitrogen and phosphorus biologically. At this pl ant, however, the influent wastewater has an insufficient concentratio n of organic substrates, thus decreasing the efficiency of the biologi cal phosphorus removal. An analysis of organic consumption in the reac tion tank on the simulation suggested that injecting primary sludge in to the reaction tank would increase the efficiency of phosphorus remov al process. Full scale experiments conducted at the plant verified the efficiency of this method. In addition, by shortening the A-SRT, ensu ring that nitrification is not negatively affected, the efficiency of the nitrogen and phosphorus removal was significantly improved. Copyri ght (C) 1996 IAWQ.