| Based on the characteristics of denitrifying phosphorus accumulating organisms (DPAOs), which can accumulating phosphorus in anoxic condition, denitrifying phosphorus removal process has effectively solved sludge age contradiction, shortage of carbon source, competition of dissolved oxygen and other problems caused by the single sludge system of the traditional nitrogen and phosphorus removal process by using "two sludge system". Induced crystallization process is a valid way to recover phosphorus resource from sewage, the product is easy to separate, with high purity, can be directly used as industrial industry material. Therefore, denitrifying phosphorus removal theory and induced crystallization theory was combined in this research, which aimed at reducing the burden of biological phosphorus removal and recovery phosphorus product as well. So as to get stable denitrification effect and high phosphorus removal efficiency the under low carbon and low energy consumption conditions.The environmental and economic benefits achieve at the same time.The successful acclimation of bacteria is the premise of the stable operation of the system, after nearly 35d’s cultivation, ammonia removal rate of nitrification sludge gradually increased from 56.2% to 99% and the nitrification rate was 2.10 mgN/gMLSS·h.The reactor was operated under anaerobic-aerobic conditions to enrich phosphorus accumulating organisms (PAOs), and then operated at anaerobic-anoxic-aerobic conditions, at the same time NO3--N was added to anoxic stage to cultivate DPAOs. After continuous running of 80 days, the denitrifying phosphorus bacteria was successfully achieved. The phosphorus accumulation amount in anoxic condition to total was over 97.5%. The batch test results indicated that, before the cultivation step 2, part of PAOs had similar characteristics to DPAOs, which can remove phosphorus by using nitrate as electron acceptor. Compared to the extracellular carbon sources, carbon sources within the cell is the most effective energy source for DPAOs to use to remval nutrient. The rate of denitrification and phosphorus removing reached to 7.41mgN/(gMLSS·h) and 3.63 mgP/(gMLSS·h) respectively.The stability of nitrogen and phosphorus removal and phosphorus recovery effect of two-sludge system combined with the induced crystallization process was investigated by comparing the treatment effect of A2N-SBR, A2N-IC-SBR and A2N-IC2-SBR process, under the condition of feed water with different ratio of nitrogen to phosphorus in artificial wastewater and domestic sewage. Results show that, the COD in the influent was 117-267mg/L, ammonia was 16-39mg/L, TP was 2-16mg/L. the removal efficiency of COD and nitrogen of three processes is basically the same, the average removal rate of 89% and 94% and 83% respectively.The results show that organic absorption and denitrification of DPAOs has not significantly influenced by the addition of chemical phosphorus removal unit. The TP removal effect and the stability of A2N-IC-SBR and A2N-IC2-SBR were better than that of A2N-SBR. By adding two-stage induced crystallization column, the total phosphorus recovery rate and the ratio of chemical phosphorus removal amount to total were increased to 82%～90% and 25%-27%, the ratio of phosphorus uptake amount to release amount was significantly decreased, which means the burden of biological phosphorus removal was reduced. However, when dealing with municipal wastewater, phosphorus recovery rate of primary induced crystallization fell by about 20%, and the volatility is more obvious than treating artificial water, due to the impurities in the inflow. But the adverse effect was weakened in the secondary induced crystallization.Under the condition of influent phosphorus concentration was 20mg/L, better phosphorus recovery effect can be achieved by using smaller size of the seed (mesh: 100～150) and appropriate aeration rate (250L/h), The recovery rate and the homogeneous crystallization rate were 64.53% and 3.45%.When there is a certain amount of alkalinity in the influent, pH value was boosted by aeration effcienctly, which is conducive to recovery of hydroxyl calcium phosphate crystal. Through the aeration to anaerobic and nitrification supernatant, it was found that the gap of initial pH, pH increasing rate and the final pH value between two kinds of supernatant is not big, moreover the nitrification supernatant was cleaner. Therefore to place the IC reactor after nitrification tank is feasible. The optimization test of induced crystallization was carried out after the IC column position moved. Experimental results show that when the calcium to phosphorus ratio is 2:1～3:1, the phosphorus recovery rate was good. The organic, colloids and other impurities in the influent were further removed during the nitrification phase, which ensure that phosphorus recovery efficiency of primary induced crystallization unit reached to 67.5%.However, the optimized for phosphorus recovery rate of secondary induced crystallization improvement is not obvious, the total recovery rate is close to the past, is about 78%The short-time aeration added after anoxic stage, helped to further improve the effect of phosphorus and ammonia removal.Simultaneous nitrification and denitrification may occur at the same time, which also had a total nitrogen removal efficiency. However,extension of rear aeration HRT may cause the changes of microbial populations in the system,which go against to the DPAOs to maintain its characteristic of phosphorus release, anoxic phosphorus removal and aerobic phosphorus accumulation.under the premise of ensuring the system removal effect of nitrogen and phosphorus,to keep a shorter rear aeration time was preferred. Under the experimental conditions,0.5～1h should be taken. |
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