Study On Cooperative Phosphorus Removal And Key Influencing Factors By Biological/Physicochemical Process

Currently, wastewater phosphorus removal technology is mainly divided into biological phosphorus removal and physicochemical phosphorus removal. Due to the biological phosphorus removal technology is influenced by many factors, the removal efficiency of TP is unstable and effluent water quality is fluctuant. While physicochemical phosphorus removal technology has stable removal efficiency of TP with requiring lots of flocculant, increasing sewage treatment costs. Biological/ physicochemical phosphorus removal technology is a new phosphorus removal technology, which combines the advantages of low-cost operation of biological phosphorus removal and the treatment effect stability of physicochemical phosphorus removal.Aiming at studying on cooperative phosphorus removal and key influencing factors by biological/physicochemical process, traditional A/O process is selected by the topic. MLSS,SRT,R these three effect factors are studied on the effects of phosphorus release and uptake and phosphorus removal on biological/physicochemical sludge, while the three factors are studied on the influence of COD, NH₄⁺-N removal and the optimal operating condition of system performance. Taking biological phosphorus removal as a control group, comparative analysis of the biological/physicochemical sludge system is better than biological sludge system in aspects of anaerobic phosphorus release, aerobic phosphorus uptake and nutrient removal. The main conclusions through the experiments are the following:â‘ The conclusions of biological/physicochemical phosphorus removal show that under the optimal conditions, as the MLSS is stable at about 3500mg/L, SRT is 8 days, R is 0.5, when the influent COD is 258.79³36.77mg/L, the NH₄⁺-N is 43.88⁵3.55mg/L, the TP is 4.97⁶.92mg/L, their average figures of effluent water quality are separately 44.54mg/L, 11.42mg/L, 0.40mg/L, the average removal rates are 85.15%, 76.56%, 93.34% respectively. The effluent water quality reaches the first Grade B standard of《the standard of pollution emissions in Urban sewage treatment plant》(GB18918-2002). Compared with the biological sludge system under the optimal conditions, TP,COD removal rates are increased by 8.27%,4.36% respectively, and when SRT is reduced greatly, the effluent NH₄⁺-N also can reach emissions standard. Under the experimental conditions, the ratio of physicochemical sludge is about 4% in the system of biological/physicochemical sludge.â‘¡SRT and MLSS have a great influence on anaerobic phosphorus release,aerobic phosphorus uptake and decontamination in biological/physicochemical sludge system. With the extension of SRT, the rate of anaerobic phosphorus release and aerobic phosphorus uptake is decreased, but the removal efficiency of NH₄⁺-N is increased, SRT has little effect on TP and COD removal rate. In order to take into account the effect of phosphorus release and uptake and nitrogen removal, under experimental conditions, SRT should take 8d, at this time the MLSS is about 3500mg/L in the system. Compared with the biological sludge system, under different SRT, the rate of phosphorus release is similar and the effect of aerobic phosphorus uptake is gradually converging when the process of aerobic phosphorus uptake tends to balance, the effect of phosphorus release and uptake is promoted by biological and physicochemical synergy.â‘¢The rates of anaerobic phosphorus release and aerobic phosphorus uptake decreased with the increase of sludge recycle ratio R, but the NH₄⁺-N removal efficiency increased with the increase of R, the R has no obvious effect on TP and COD removal. In order to take into account the capacity of phosphorus release and uptake and nitrogen removal, under the experimental conditions, the sludge recycle ratio 0.5 is better. Compared with the biological sludge system, under different R, the rate of phosphorus release is similar and the effect of aerobic phosphorus uptake is gradually converging when the process of aerobic phosphorus uptake tends to balance, the effect of phosphorus release and uptake is promoted by biological and physicochemical synergy.