A Comparative Study On Mechanism Of Nitrogen And Phosphorus Removal And Metabolic Activity Of Microorganism Between Reversed A~2/O Process And Conventional A~2/O Process

Water pollution and eutrophication have become high-profile global issues. The reason of eutrophication is the concentration of nitrogen and phosphorus in water is too high. Effectively control nitrogen and phosphorus emission is the fundamental way to solve the problem. Therefore, municipal wastewater biological nutrient and phosphorus removal technology has increasingly become a hot issue in the field of sewage treatment.Based on plenty experiments on nitrogen and phosphorus removal effect, Bo Zhang et al. firstly proposed reversed A~2/O process. Because of the pre-anoxic, carbon source for nitrogen removal was satisfied preferentially, at the same time, the adverse effects toward anaerobic environment induced by the nitrate in the returning sludge had been avoided. Many inherent contradictions and bottlenecks in biological nutrient and phosphorus removal system had been completely solved. Moreover, the practical application outcome of reversed A~2/O process in Licunhe WTTP and Tuandao WTTP indicated that reversed A~2/O process had obvious characteristics of energy saving. Based on the previous research, this test was designed to research the nitrogen and phosphorus removal capacity and the metabolic activity of activated sludge in order to analyze the differences on nitrogen and phosphorus removal and energy saving mechanism between reversed A~2/O process and conventional A~2/O process. The results show that:(1) Whether in high-load or low-load carbon conditions, reversed A~2/O process had better removal efficiency on organic pollutants, nitrogen and phosphate than conventional A~2/O process, in which the superiority of phosphorus removal was most obvious. Reversed A~2/O process had higher nitrification rate and denitrification rate. The PAOs in reversed A~2/O process had higher phosphorus uptake rate in aerobic condition, and can get a better phosphorus removal effect with lower phosphorus release capacity.(2) Whether in high-load or low-load carbon conditions, although lower PHB content was generated in reversed A~2/O system under anaerobic conditions, because of the PHB comsumption under aerobic phase in conventional A~2/O process, higher PHB content had been induced into the aerobic zone compared with conventional A~2/O system. Furthermore, the phosphate uptake rate of reversed A~2/O process under aerobic conditions was higher than that of conventional A~2/O process under anoxic or aerobic conditions. The results indicated that the reasons of better phosphate removal effect of reversed A~2/O process were the increased available energy and the higher energy utilization efficiency under aerobic conditions. (3) Whether in high-load or low-load carbon conditions, the TTC-DHA activity, INT-ETS activity and SOUR of reversed A~2/O process were higher than that of conventional A~2/O process. The reversing of anaerobic and anoxic enhanced the metabolic activity and biochemical reaction efficiency of activated sludge in aerobic phase, resulting in a higher aerobic biological degradation rate and oxygen utilization rate. The activity of microbial populations in reversed A~2/O process had a stronger carbon metabolism and metabolic efficiency than conventional A~2/O process.