Effect Of Influent Ammonia Concentration On Biological Nutrient Removal In Sequencing Batch Reactor Operated As Oxic/Anoxic/Extended-idle Regime

Nowadays, eutrophication caused by excess discharge of nutrients(nitrogen and phosphorus) has been increasingly serious. Scholars at home and abroad have explored various nutrient removal processes and achieved excellent removal efficiencies. Many of which, biological nutrient removal(BNR) received extensive attention because of its excellent removal efficiencies. In this work a novel BNR regime operated as oxic/anoxic/extended-idle sequencing batch reactor(O/A/EI-SBR) which was based on the aerobic/extended-idle regime was proposed to investigate the BNR performance. There is an anoxic stage followed the aerobic stage to achieve the nitrogen removal. Oxic/anoxic/extended-idle SBR achieved perfect phosphorus removal efficiencies without anaerobic phase existence. The effects of influent ammonia concentration on BNR efficiencies of oxic/anoxic/extended-idle SBR was explored in this work.The effects of ammonia concentration in R1, R2 and R3(20, 40 and 60 mg·L-1) on biological nutrient removal in sequencing batch reactors operated as oxic/anoxic/extended-idle regime were investigated. Nitrogen, phosphorus and intracellular storage polymers were analyzed in a typical cycle, and the mechanism for different ammonia concentrations on BNR performance in the O/A/EI SBR was explored. Experimental results show that 96.6%,90.1% and 81.8% of the total phosphorus and 93.1%, 74.9% and 60.0% of the total nitrogen were removed when ammonia concentration was at 20, 40 and 60 mg·L-1, respectively. Simultaneous nitrification-denitrification(SND) was observed in the three systems and achieved respective 21.3%, 28.6% and 35.9% of TN elimination. In addition, phosphorus removal was also observed in anoxic stage in R2 and R3,and achieved 13.8% and 11.3% of TP elimination respectively.It is demonstrated that ammonia concentration in influent has impacts on oxic phosphorus uptake and release, polyhydroxyalkanoates(PHAs) formation, anoxic denitrification, as well as phosphorus release during idle stage. The higher ammonia concentration is, the less carbon source for PHAs synthesis, which usually inhibits phosphorus uptake. Higher ammonia concentration also leads to incomplete denitrification and ultimately reduce BNR performance.