Effect Of Dissolved Oxygen Concentration On Biological Nitrogen And Phosphorus Removal In Oxic/Extend-idle Sequencing Batch Reactor

In recent years, with nitrogen and phosphorus pollution is increasingly seri ous, the removal of nitrogen and phosphorus and other nutrients in water has become more and more important. In this study, the effect of dissolved oxygen(DO) concentration on biological phosphorus and nitrogen removal in oxic/exte nded-idle sequencing batch reactors was investigated, and use sodium acetate as the sole carbon source in synthetic wastewater. System operation cycle is: infl ow?aerobic(4 h)?settling(0.5 h)?effluent?idle(3.5 h), the DO concentration o f R1, R2, R3 and R4 is controlled at 1, 2, 3, and 4 mg/L in the aerobic phas e respectively. The research results show that simultaneous nitrogen and phosph orus removal can be found in the O/EI process, and the effect of DO concentr ation in aerobic phase on phosphorus and nitrogen removal performance of the system is remarkable.As a result, the low DO concentration of 1 mg/L drove a high phosphorus removal efficiency of 96% and a high phosphorus uptake of 5.02 mg-P/g-VSS, while phosphorus removal efficiency decreased to 50% and the phosphorus uptake reduced to 2.81 mg-P/g-VSS when the reactor operated at a high DO level of 4 mg/L. The results suggested that microbes can synthesize more polyhydroxyalkanoates(PHAs) under the DO concentration of 1 mg/L, less glycogen synthesis and utilization, meanwhile aerobic phosphorus uptake and poly phosphate release in the idle period under the DO concentration of 1 mg/L are much higher than that in other reactors. DO concentration can affect the phosphorus removal performance of the O/EI system by influencing the synthesis and utilization of intracellular polyhydroxyalkanoates and glycogen, idle phosphorus release, as well as aerobic phosphorus rele ase and uptake.Ammonia removal efficiency were all over 98% in this study, the low DO concentration of 1 mg/L can meet the requirements of ammonia removal, and with the increase of the DO concentration, the concentration of ammonia in effluent have no obvious reduced. R1, R2, R3 and R4 reactors total inorganic nitrogen(TIN) content were 4.75, 5.05, 5.17 and 7.04 mg/L in effluent, and TIN removal efficiency were 85%, 80%, 80% and 85% respectively. Nitrogen removal efficiency in R1 is better than other reactors, and it's nitrogen removal quantity reach to 9.57 mg-N/g-VSS. Simultaneous nitrification-denitrification(SND) was observed in R1~R4 reactors and achieved respective 18%, 14%, 11% and 8% of TN elimination. The experimental results show that the DO concentration has significant effects on nitrogen removal performance in the O/EI regime, and the low DO concentration of 1 mg/L drove a better nitrogen removal performance.