Carbon, nitrogen and phosphorus removal from domestic wastewater by alternating aerobic-anoxic process

Abstract

excessive amount of nutrients (nitrogen and phosphorus) released from wastewater may lead to degradation of the receiving water and can induce adverse effects on human health and the environment. the use of coupled nitrificationdenitrification can significantly remove major pollutants from domestic wastewater, however researchers only have limited understanding of the alternating aerobic-anoxic process in a single reactor and therefore needs to be verified. this study performed treatment using an alternating aerobic-anoxic (aaa) process in a single reactor to remove major pollutants from domestic wastewater i.e., carbon, nitrogen and phosphorus. comparative analysis of the coupled nitrification-denitrification reactions was carried out to investigate different periods of nitrification-denitrification cycles and to analyse the effect of initial dissolved fe/p molar ratio and ph on ironhydroxide- phosphate precipitation. the results indicated that 3-h aerobic digestion and 3-h anoxic time was the best cycle to remove the pollutants where the removal efficiencies of cod and nh4 + were verified as high as 97% and 87%, respectively, achieving the desired inorganic nitrogen concentration of less than 10 mgnl-1 in the outflow to meet stringent effluent standards. the denitrification/ nitrification ratio of 2.1, indicates that denitrification occurs in the reactor faster than nitrification because it can prevail over nitrifying bacteria in competition for reaction kinetics. the aaa treatment process to remove soluble reactive and total phosphorus from domestic wastewater had a moderate efficiency. two types of fe4(oh)9po4 and fe5(oh)6(po4)3 precipitate may occur in different conditions of the aaa process. the results advance the understanding that proper aaa treatment effectively removes carbon, nitrogen and phosphorus pollution from domestic wastewater. the contribution of this study in removal of major pollutants from domestic wastewater will require future assessment in a prospective wastewater treatment facilities setting.