The alternating aerobic-anoxic system for the treatment of phosphorus in waters

Abstract

The discharge of excessive amounts of phosphorus (P) from domestic wastewater treatment plant effluent is of interest in this study because the abnormally high levels of P as one of the nutrient elements can lead to eutrophication for the receiving waters. Although many methods have been proposed for the removal of P matter from industrial and municipal wastewater, such as Phoredox, A2OTM and UCT-type, the use of alternating aerobic-anoxic (AAA) system must be verified. This study proposes the use of Discontinuous Aerobic-Anoxic Reactor to remove P from domestic wastewater treatment plant effluent using the nitrification and denitrification type of activated sludge. The objectives of this study are: (1) to evaluate the efficiency of P removal from domestic wastewater treatment plant effluent by a single reactor under aerobic digestion (AD) condition, and (2) to assess the performance of AAA process of using the different cycles of nitrification-denitrification to remove P from domestic wastewater treatment plant effluent. The average efficiency of AD to remove P from domestic wastewater treatment plant effluent was 48%. The efficiencies of AAA system to remove P from domestic wastewater treatment plant effluent, were verified as follows: (1) at 6 h AD and 6 h anoxic time (AT), (2) at 5 h AD and 5 h AT, (3) at 4 h AD and 4 h AT, (4) at 3 h AD and 3 h AT, and (5) at 2 h AD and 2 h AT, resulting to the average removal efficiencies of 0, 48, 82, 91, and 88%, respectively. The AAA system has exhibited a better performance compared to AD. The best condition of AAA system had a period of 3 h AD and 3 h AT and reached 91% efficiency with an average treated effluent concentration of less than 1.0 mg L–1 P. High performance of the AAA process has been proven, giving new insights into environmental engineering practices.