| A large quantity of excess sludge generated in biological wastewater treatment has not only caused the tremendous pressure on the environment, and its high cost of treatment and disposal has become a bottleneck restricting water industry. In addition, with increasing eutrophication, nitrogen and phosphorus in wastewater treatment has been the research focus, while the traditional nitrogen and phosphorus removal technology has the problem of carbon insufficiency,bacteria competition, difficulty to control SRT, and many other issues. So far, there is no high-efficiency and low-energy consumption, pollution-free waste water treatment technology with sludge reduction and nitrogen and phosphorus removal. Therefore, development wastewater biological treatment process of nitrogen and phosphorus removal simultaneously, sludge production minimize without reducing the treatment efficiency is better way to solve the sewage problem.Aiming at the problem of a great amount of residual sludge in current biological wastewater treatment process and the status that nitrogen and phosphorus removal is difficult to achieve the best results at the same time in the traditional biological nitrogen and phosphorus removal process, wastewater treatment process with integration of low sludge yield, nitrogen and phosphorus removal was explored. Therefore, this study developed a biological wastewater treatment process of simultaneous nitrogen and phosphorus removal and sludge reduction by making use of the characteristics, of which denitrifying phosphorus removal bacteria (DPB) uptake phosphorus in the hypoxic environment, compound denitrifying phosphorus removal-BAF (CDPR-BAF) process. CDPR-BAF process is the two-sludge system on the combination of the biofilm and activated sludge. The process by setting the BAF as a nitrification segment, not only provided electron acceptor for the denitrification in anoxic, but also made nitrifying bacteria and denitrifying phosphorus removing bacteria growth in their optimal environment. By adjusting the sludge age (SRT) increased activity that denitrifying phosphate accumulating bacteria in anoxic uptake P to achieve maximum, adopted the method reducing return sludge ratio to avoid the NO3--N in the return sludge impact on anaerobic phosphorus release. Focus on studied the nitrogen and phosphorus removal efficiency and sludge reduction when using the compound process to treatment domestic wastewater, process control parameters and many effect factors were investigated in advance, the results indicate that:①In CDPR-BAF system, under the condition of SRT=15d, while influent COD =185～386 mg/L,NH4+-N =18.5～40 mg/L,TN=20.8～44.5 mg/L,TP=5.31～10.6mg/L,DO of BAF outlet=1～1.5mg/L,sludge recycle ratios=0.3～0.4, the removal rates of COD,NH4+-N, TN and TP are 90.5%, 89%, 81% and 92.3% respectively. effluent water quality reaches first-degree B standards of《letting standards of town sewage treatment plant》(GB18918-2002). In this system, sludge yield Ys is 0.16gMLSS/gCOD, which shows that comparing with traditional activated sludge process 0.30gMLSS/gCOD, the effect of sludge reduction in system reaches 47%.②SRT and MLSS effect has an important influence on the decontamination in system. If SRT is too large, aging micro-organisms still present in the system, affecting the activity of the sludge, but the SRT cannot be too short, otherwise the MLSS in system cannot be guaranteed, thus affecting treatment effect. By setting different SRT to investigate the phosphorus removal in system, the results showed that: in the SRT=15 days condition, nitrogen and phosphorus removal of the system has maintained a good state, and the growth sludge of system have stabilized, anaerobic tank, anoxic and post-aeration tank sludge concentration has been between the 3674 4705 mg/L.③By changing the aeration to adjust DO concentration of BAF can achieve the maximum removal of pollutants, the DO concentration scope of BAF export 1.5 2 mg/L is more appropriate to the system, if higher than this value range, DPB P uptake and denitrification decreased with the DO concentration increasing.④NH4+-N removal rate decreased with the rise of system reflux ratio, and the TP removal is different from NH4+-N removal, the higher the sludge recycle,the lower effluent TP concentrations, the better the removal efficiency. Therefore, there is an optimum range reflux ratio, since this process is the post-denitrification, there is no need to increase sludge return ratio to improve nitrogen removal rate, under the experimental conditions the sludge recycle ratio 0.3 to 0.4 was better.
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