The Combined Process Of Anaerobic/aerobic-anoxia SPNDPR+ANAMMOX Realizes The Optimized Operation Of The Deep Nitrogen And Phosphorus Removal Of Low-C/N Municipal Wastewater

In view of the shortage of carbon source in traditional biological nitrogen and phosphorus removal process,the competition between nitrogen and phosphorus removal bacteria for dissolved oxygen?DO?,and the contradiction between different functional bacteria in sludge age?SRT?,a new process of simultaneous nitrogen and phosphorus removal,namely the combined process of simultaneous partial nitrification-endogenous denitrification phosphorus removal and anaerobic ammonia oxidation?SPNDPR+ANAMMOX?,was proposed based on the water quality characteristics of low C/N municipal wastewater.The anaerobic/aerobic SPNDPR system was first started in this experiment,which is an essential part of the combined process of SPNDPR+ANAMMOX.This study focused on the nitrogen?N?and phosphorus?P?removal performance optimization of simultaneous partial nitrification-endogenous denitrification and phosphorus removal?SPNDPR?systems.An anaerobic?180 min?/aerobic operated sequencing batch reactor?SBR?fed with domestic wastewater was used for investigating the startup and optimization of SPNDPR by regulating the aeration rate and aerobic duration time.The experimental results show that,at aerobic aeration rate of 0.8 L·min^-1 and aerobic duration time of 150min,the effluent PO₄^3--P concentration was about 1.5 mg·L^-1,with the effluent NH₄⁺-N and NO₃^--N concentrations gradually decreased from 10.28 and 8.14 mg·L^-1 to 0 and 2.27mg·L^-1 and effluent NO₂^--N concentration increased to 1.81 mg·L^-1.When the aeration rate was increased to 1.0 L·min^-1 and the aerobic duration time was shortened to 120 min,the phosphorus removal and partial nitrification-endogenous performance of the system gradually increased,but the total nitrogen?TN?removal performance decreased first and then increased gradually.The final effluent PO₄^3--P,NH₄⁺-N were stably below 0.5 and 1.0mg·L^-1,aerobic nitrite accumulation and SND efficiencies were 98.65%and 44.20%,respectively,and TN removal efficiency was 80.33%.The concurrence of aerobic phosphorus absorption,denitrifying phosphorus removal,partial nitrification,and nitrification-endogenous in the aerobic stage of the SPNDPR system ensured the simultaneous N and P removal from low C/N wastewater.In order to further understand the nitrogen and phosphorus removal performance of SPNDPR system in treating low C/N municipal wastewater under different aeration volume and aerobic time.An anaerobic?180 min?/aerobic operated sequencing batch reactor?SBR?fed with urban sewage was optimized by regulating aeration quantity[the volume of a gas per unit volume of reactor passed in unit time,the unit is L·?min·L?^-1.from 0.125 L·?min·L?^-11 gradually to 0.025 L·?min·L?^-1]and aerobic time?from 3 h to 6 h?,to investigate the for deep-level nitrogen?N?and phosphorus?P?removal.The experimental results show that the effluent NH₄⁺-N,NO₂^--N,NO₃^--N and PO₄^3--P concentrations of the optimized SPNDPR system were 0,8.62,0.06 and 0.03 mg·L^-1;the effluent TN concentration was about 9.22 mg·L^-1,and the TN removal efficiency was up to 87.08%.When the aeration quantity was decreased from 0.125 L·?min·L?^-1 to 0.100 L·?min·L?^-1 and 0.075 L·?min·L?^-1,respectively,the nitrification rate of the system could be recovered and stabilized at 0.16mg·?L·min?^-1.However,when the aeration quantity continuously decreased to 0.050L·?min·L?^-1 and 0.025 L·?min·L?^-1,respectively,the nitrification rate decreased to 0.09mg·?L·min?^-1 and 0.06 mg·?L·min?^-1.With the reduction of aeration quantity[from 0.125L·?min·L?^-1 to 0.100,0.075,0.050 and 0.025 L·?min·L?^-1]and extension of aerobic time?from 3 h to 6 h?,the TN removal efficiency increased gradually from 62.82%to 87.08%,and the SND efficiency increased from 19.57%to 72.11%.It was proved that reducing the aeration quantity can enhance the SPND function and realized the deep denitrification of the system.By enhancing the anaerobic intracellular carbon storage and aerobic phosphorus uptake,denitrifying phosphorus removal,partial nitrification,and nitrification-endogenous realized,the SPNDPR system after reducing aeration and prolonging aerobic time realized the deep-level denitrification and dephosphorization from low C/N urban sewage.In order to understand the characteristics of nitrogen and phosphorus removal by SPNDPR+ANAMMOX combined process,the low C/N?<4?municipal wastewater was treated in this study.By delaying anaerobic/aerobic segmented drainage?anaerobic and aerobic end-drainage part?,combined control of aeration amount and aeration time in the aerobic section,the mixed drainage suitable for the operation of ANAMMOX-SBR reactor could be obtained through anaerobic ammonia oxidation.After the reaction,the drainage water returns to the SPNDPR-SBR reactor again,and the denitrifying phosphorus removal reaction can continue.The whole process can realize the optimal operation of SPNDPR+ANAMMOX system.The results showed that the optimized effluent COD,PO₄^3--P,NH₄⁺-N,NO₂^--N and NO₃^--N concentrations were stable at 37.51,0.01,0.09,0 and0.11 mg·L^-1,respectively.COD removal rate,PO₄^3--P removal rate,TN removal rate and SND removal rate were stable at 81.16%,99.91%,99.35%and 49.29%.It shows that SPNDPR+ANAMMOX combined process has good performance of deep nitrogen and phosphorus removal.In the typical aerobic stage?180³60 min?of SPNDPR+ANAMMOX combined process,PO₄^3--P was removed in the first 90 min,and nitrification continued to convert NH₄⁺-N to NO₂^--N.At the end of aerobic stage,the concentration of NH₄⁺-N was less than 1 mg·L^-1,the concentration of NO₂^--N was 17.23 mg·L^-1,and the concentration of NO₃^--N was less than 1 mg·L^-1.Furthermore,the 16S rRNA biodiversity analysis showed that AOB remained stable at about 4.48%and NOB decreased from 0.17%to 0.04%.The results show that the operation mode of the combined process will not destroy the partial nitrification-endogenous process,and can maintain the growth of AOB,continue to inhibit and wash out the NOB in the system.During the typical period of hypoxia?560⁶80 min?in which SPNDPR+ANAMMOX combined process operated steadily,the concentration of COD decreased slightly(decreased by 8.10 mg·L^-1),but the concentration of PO₄^3--P,NO₃^--N and NO₂^--N decreased gradually from 5.43 mg·L^-1,2.97 mg·L^-1 and 6.37 mg·L^-1 to 0mg·L^-1,respectively,and DPAOs increased from 0.13%to 1.19%by 16s rRNA biodiversity analysis.It shows that there is obvious denitrification and phosphorus removal in the system,and the internal carbon source stored in the anaerobic section will not be lost completely after the aerobic section and the static section.The increase of COD and DO concentration in ANAMMOX-SBR reactor after the change of feed water?from water distribution to SPNDPR-SBR reactor sectional drainage mixture?has a certain impact on the biodiversity of ANAMMOX-SBR reactor.ANAMMOX bacteria increased significantly from 11.75%to 31.42%.This indicated that it was beneficial to the rapid enrichment of ANAMMOX bacteria in low organic matter concentration(COD was about 50 mg·L^-1,water distribution did not contain organic carbon source),and was most suitable for the growth of anaerobic ammonia oxidizing bacteria of Candidatus Kuenenia.