Research on High-Concentration Activated Sludge Method for Energy-Efficient Nitrogen Removal in Wastewater

Currently, there is an increasing emphasis on energy conservation and emission reduction, and conventional water treatment processes can no longer meet the demand. Enhancing the reflux ratio of the mixed liquor is a promising option to improve nitrogen removal in wastewater treatment. However, a high reflux ratio can lead to a significant carryover of dissolved oxygen (DO), which can negatively impact the denitrification process. Research in this area is still relatively limited. The high concentration activated sludge method can significantly reduce the impact of dissolved oxygen. Therefore, this study compares it with the conventional internal recirculation method in terms of pollutant removal and dissolved oxygen recovery. It explores the feasibility of using high concentration activated sludge to enhance nitrogen removal in wastewater treatment while achieving energy savings, and calculates the potential energy savings achieved. The results indicate that employing the high concentration activated sludge method to increase the sludge concentration in the system not only prevents the detrimental effects of dissolved oxygen on the anoxic zone but also enhances the system's removal rates for BOD ₅ , CODcr, ammonia nitrogen, and total nitrogen (TN). The study calculated that the Air-lift technique using aeration pumps recovers approximately 31.46% of DO. However, the biochemical treatment system used in this experiment is relatively small in scale, which limits its ability to fully demonstrate the energy savings and management advantages associated with the high concentration activated sludge method.