Study On Efficiency And Optimization Of Denitrification Phosphorus Removal In ABR-MBR Combined Process

In order to achieve a stable,energy-saving multi-functional removal of pollutants target,the ABR-MBR combined process with microbial phase separation and efficient acid-producing operation were adopted to provide high-quality carbon source for denitrification phosphorus removal process.Effective conversion and removal of carbon,nitrogen and phosphorus through control and coordinated competition regulation.In this study,the start-up of denitrifying phosphorus removal process with anaerobic/aerobic operation mode.The effect of different influencing factors on the system was investigated in order to optimize the operating conditions of the ABR-MBR process.The main contents and conclusions are as follows:1.The nitrogen and phosphorus removal characteristics during the start-up and the long-term operational stability of an anaerobic/anoxic?A/A?ABR coupled aerobic MBR system treating low C/N domestic wastewater were investigated.Results showed that the denitrifying phosphorus bacteria?DPBs?were enriched successfully within 46 days by controlling the nitrate recycling ratio increasing from 150%to300%,with the temperature around 30?±2?,the hydraulic retention time of 12hours and sludge reflux ratio of 80%in the ABR,the sludge retention time?SRT?in denitrifying phosphorus removal functional area of 25 days,and the dissolved oxygen?DO?of 1-2 mg·L^-11 in the MBR.The net phosphorus release amount and phosphorus uptake amount of denitrifying phosphorus bacteria reached 20.56 mg·L^-11 and 27.74mg·L^-1,respectively.Results also showed that about 84.8%of phosphorus accumulating bacteria?PAOs?could use NO₃^--N as an electron acceptor for denitrifying phosphorus removal.During the following 50 days'stable operation after the system start-up,the average removal rates of COD,NH₄⁺-N,TN and PO₄^3--P were91.8%,99.0%,71.5%and 94.2%,respectively.It suggested that 0.83 mg·L^-11 NO₃^--N was consumed per 1 mg·L^-11 PO₄^3--P was removed during the denitrifying phosphorus removal.2.The effect of HRT on the performance of ABR-MBR denitrification phosphorus removal system was studied.The results showed that the change of HRT had little effect on the overall COD removal performance of the system,and the COD removal efficiency was maintained stably at more than 90%.However,the change of HRT had a great impact on the utilization of high-quality carbon sources by DPBs.When the HRT is 12h,9h and 6h,the average phosphorus removal efficiency in the system is92.56%,94.87%and 67.31%,respectively,while the average nitrogen removal efficiency is 71.08%,73.15%and 59.4%,respectively.HRT is an important factor that leads to the reduction of nitrogen and phosphorus removal efficiency.Much too long HRT resulted in the ineffective use of PHA,whereas too short HRT caused the incomplete absorption of VFA.Results also showed that 84.8%,85.6%and 68.2%of PAOs were able to use NO₃^--N as electron acceptor for phosphorus removal when the HRT was 12h,9h and 6h,respectively.3.The optimization of the denitrifying phosphorus removal rate and the utilization of high-quality carbon sources were obtained by optimizing the system HRT.Results showed that gradually increase of influent substrates concentrations resulted in the increase of ABR volume loading rate?calculate of COD?from 1.02kg·?m³·d?^-11 to1.53kg·?m³·d?^-1,2.04kg·?m³·d?^-11 and 2.55 kg·?m³·d?^-1.By gradually domesticating the tolerance of DPBs to NO₂^--N,and hence the synergistic effects of different microorganisms and the performance of the system both can be optimized.Sufficient ammonia concentration and the inhibition of NOB are the keys for the stable operation of short-cut nitrification.With the increase of influent substrates,the denitrifying phosphorus removal efficiency was first increases and then decreases.When the volume loading rate was 2.55kg·?m³·d?^-1,the average effluent NO₂^--N concentration was 24.9 mg·L^-1,which had a serious inhibitory on DPBs,resulting in the lowest phosphorus uptake.