Sludge reduction and nutrient removal from an anaerobic/anoxic/oxic(A2/O) process coupled with a modified oxic-settling-anaerobic process

There is little research that focused on both nutrient removal and sludge reduction based on an anaerobic/anoxic/oxic(A2/O) process. In this study, two systems that consisted of an A2/O process combined with a modified oxic-settling-anaerobic (MOSA) reactor were run for 200 d at the lab-scale to evaluate their effect on sludge reduction and their influence on nutrients removal. The MOSA reactor was run a hydraulic retention time of 5 d and interchange rate of 10%. Our results showed that A2/O-MOSA system performed as well as an A2/O system for removing Chemical Oxygen Demand (COD), ammonia, total nitrogen, and total phosphorus. The A2/O-MOSA system removed an average of 92% of the influent COD, slightly higher than that in the A2/O (90%) system. As for sludge reduction efficiency, the A2/O-MOSA process achieved a sludge reduction of 24%and sludge decay contributed 58% to this sludge reduction.