ADVANCED BIOLOGICAL ENHANCED NUTRIENT REMOVAL PROCESSES BY THE ADDITION OF ROTATING BIOLOGICAL CONTACTORS

Advanced removal efficiency of organic carbon, phosphorus and nitrogen from municipal wastewater was achieved by using an anaerobic-anoxic-o xide (A2/O) process with the addition of fully and partially submerged RBC biofilms. The experiments were carried out in a range of F/M rati o 0.21 to 0.32 kg BOD/kg MLSS/d and at a various total hydraulic deten tion times (HRT), return activated sludge ratio (r) and mixed liquid r ecycle ratio (R). Another pilot plant A2/O process without adding RBC was conducted for control experiments. Compared with A2/O process, thi s new process could achieve a higher degree of nitrification rate with out decreasing the removal efficiencies of organic carbon and phosphor us. The new process provides an environment for combining the long sol id retention time (SRT) biofilm and the short SRT suspended activated sludge. This concept can resolve the conflict in SRT between nitrogen and phosphorus removal simultaneously. Correspondingly, the benefits o f the new process are shorten the hydraulic detention time, progress t he efficiency of nutrient removal, more stable for operation and more economic for required land cost. (C) 1997 IAWQ. Published by Elsevier Science Ltd.