Study On Characteristics Of Phosphorus Removal By A Coupling Process Of Modified UCT And Biofilm

At present, the effect of phosphorus removal was not ideal in urban wastewater treatment plant owing to carbon competition, sludge age contradiction and the influence of nitrate to phosphorus release and so on. Generally chemicals are added to meet water quality standards. In this case, it was necessary to develop a coupling process of modified UCT and biofilm, and the step-feed technology and aerobic biofilm technology were used in this process.The coupling process was started by acclimation of activated sludge and formation biofilm for a period of two months. After then the concentrations of denitrifying phosphorus bacteria in the system had been continuously rising, and stable at a higher concentations at last. At the same time, the removal effect of COD, NH4+—N, TNand TP were fine in the system.The effect of different pollutants removal along the reactor had been analysed during the process stability. Since the step-feed from ananerobic and anoxic zone had been used in this process, the influent carbon had been uniformly distributed in the reactor. COD was preferentially used by phosphorous bacteria and denitrifying phosphorous bacteria, so that the number of heterophic bacteria in the aerobic zone was reduced, the aeration rate was reduced and the energy was saved, and the microbial degradation was given better play. The nitrogen emission pathways in the system were as followed:effluent, excess activated sludge, denitrification, simultaneous nitrification and denitrification, and microbial assimilation. Nitrogen was removed primarily in the anoxic and aerobic zone in different levels, and the nitrogen removal efficiency of this system had been higher than the traditional nitrogen and phosphorus removal processes by analysis. The phosphorus emission pathway in the system was primary excess activated sludge. The reactions of denitrification phosphorus removal in the first anoxic zone and aerobic phosphorus removal in different aerobic zones had maken TP effluent concentration meet emission requirements, illustrating that the effect of denitrification phosphorus removal can not be overlooked.The effect of denitrification phosphorus removal had been strengthened by return sludge ratio R and reflux ratio r. Features and benefits in the coupling process were studied, and appropriate parameter ranges were chosen.Three kinds return sludge ratio R(R=50%±5%, R=100%±5%, R=150%±5%) and Three kinds reflux ratio r(r=50%±5%, r=75%±5%, r=100%±5%) were chosen to study, aiming to slect the best R and r in the system for better denitrification phosphorus removal.The coupling process of modified UCT and biofilm has been an energy-saving, high efficient and stable wastewater treatment process. The best work condition and the better water quality were achieved by adjusting the operation parameters, which can provide technical support for new wastewater treatment plants and renovation and expansion wastewater treatment plants.