Study On Simultaneous Nitrogen And Phosphorus Removal In Sequencing Batch Reactor

In recent years, it is serious increasingly that the nitrogen, phosphorus compound causes the phenomenon of water pollution and water eutrophication. Therefore, the treatment of the wastewater not only needs to remove COD, but also still needs to take off nitrogen and phosphorus from the sewage. This requires a wastewater treatment system to possess many kinds of treatment functions.The experiment of simultaneous nitrogen and phosphorus removal with an inner-loop sequencing batch reactor will be introduced in this paper. In the course of nitrogen and phosphorus removal of municipal wastewater with inner-loop SBR, wastewater enter the aeration phase directly, without anaerobic phase, which was conventionally considered as a key phase for phosphorus removal, but a predominant phosphorus result still can be achieved.The experimental results showed that COD, NH4+-N, and TP can be removed efficiently after 4 hours aeration, during which dissolved oxygen concentration was at 6mg/L at the beginning of aerobic phase and pH was in the rang of 7.5~8.5.The COD and NH4+-N as well as TP concentration in the effluent were about at 4~48 mg?L-1,0~2.0 mg?L-1, and 0~1.4 mg?L-1 respectively, which indicated the removal rate for each item were about 89.7%±6.5%,97.4%±3.6%,95.6 %±4.4% when the concentration of influent were about 170~260 mg?L-1, 20~30 mg?L-1, 8~20 mg?L-1,respectively.The removal rate of TIN(TIN= NH4+-N +NO3--N+NO2--N) was also reached about 70%. It was found during the research process that phosphorus removal can be achieved without anaerobic phase, which was conventionally considered as a key phase for phosphorus removal,and this phenomena can not be explained by traditional theory.To investigate the phenomena on biological phosphorus removal which appeared in this experiment, parallel experiments were conducted with both an inner loop sequencing batch reactor and a traditional sequencing batch reactor in March 2006. The experimental results showed that phosphorus removal could be achieved both inner loop sequencing batch reactor and traditional sequencing batch reactor without anaerobic phase, which was conventionally considered as a key phase for phosphorus removal,the research also found the effect of phosphorus removal was correlated with the quantity of carbon source (C6H12O6). Phosphorus concentration in the effluent was about 1.5~5.5 mg?L-1 after 4 hours aeration, and phosphorus could be continue removing to 1 mg?L-1 below by adding carbon source (COD concentration was about 100~200mg?L-1) after 2 hours aeration, during which dissolved oxygen concentration was at 6mg/L at the beginning of aerobic phase and pH was in the rang of 7~8. Which indicated the removal rate of phosphorus was above 90% when the COD and phosphorus concentration of influent were about 200 mg?L-1, 8~20 mg?L-1, respectively. Intracellular storage of poly-phosphate (poly-P) was increasing in the 4 hours aeration (the content of poly-P was 5.78mg/ g·SS at the beginning of aerobic phase, and the content of poly-P was 9.05mg/g·SS in the end) and releasing partly in the 3 hours idle-zone (the content of poly-P was 5.90mg/g·SS in the end of deposition), but the energy storage poly-β-hydroxybutyrate (PHB) was constant nearly and the content was very low(PHB concentration was about 5mg?L-1). The researches indicated that phosphate could be transformed to poly-P by poly-phosphate-accumulating organisms without anaerobic zone and PHB when the carbon source was enough, biological phosphorus removal was obtained by removing sludge with rich phosphorus.