Nutrient removal processes for low strength wastewater

Abstract

For nutrient removal from low strength wastewater, biological nutrient removal (BNR) processes available at present are not efficient due to the shortage of organic carbon. By using the carbon source obtained from the degradation of return sludge, it was attempted to enhance the efficiency of denitrification and phosphorus release. Based on its degradation mechanism, the ENR (Endogenous Nitrate Respiration) process was developed and compared with the conventional A(2)/O (Anaerobic/Anoxic/Aerobic), MUCT (Modified University of Cape Town) processes. In the experiment, the specific phosphorus release rates of A(2)/O, MUCT, and ENR processes were 0.8, 2.3, and 2.6 mg PO4-P g(2) MLVSS-h. As the nitrate concentration decreased below 3.0 mg NO2-N I-1 due to the endogenous nitrate respiration, the effluent nitrate of the ENR process was lower than the A(2)/O process and the MUCT process by 25% and 10% while the phosphorus removal efficiencies increased by 15% and 6%, respectively. It was found that the ENR process was an effective and economical alternative for removing nutrient from low strength wastewater.