Study On Characteristics Of Combined Process Of A~2O Sludge In Suit Reduction Coupled Phosphorus Removal By Side-stream

The annual increase in excess sludge production has gradually become an economic burden for the operation of sewage treatment plants,and there is a potential ecological environmental hazard.With the increasingly stringent requirements for wastewater discharge standards,sludge treatment and disposal standards in China,simultaneous enhancement of pollutant removal and sludge in-situ reduction coupling technology are the focus of future research.In this study,the use of floating spherical carries with compound materials?FSC?and suspended carriers with cross inside and longitudinal fins outside?SC?as biofilm carriers to build sequencing batch biofilm reactor?SBBR?induced sludge in situ reduction;the observed sludge yield(Y_obs)and pollutant removal efficiency of the _FSCSBBR and _SCSBBR reactors were compared,and the minimum excess sludge production and operating conditions for pollutant removal were optimized;the beaker experiment deeply analyzed and discussed the potential mechanism of sludge in situ reduction in SBBR reactors with different carriers.At the same time,a sewage treatment combined process for enhanced sludge reduction in situ and simultaneous efficient removal of pollutants was constructed,A²O sludge in situ coupled side stream crystallization phosphorus removal process?A²O-SIC?.The FSC carriers were added in traditional A²O system to form the biofilm.In this study,the optimal conditions for the side stream crystallizing phosphorus removal column operation was optimized;the influence of the side stream crystallizing phosphorus removal units on the efficiency of mainstream biological processes and the population structure of microorganisms was investigated;the excess sludge production and effluent quality during the long-term operation of the A²O-SIC combined process was examined;and analysis the coupling mechanism of A²O mainstream biological process and SIC unit.The sludge reduction effect of FSC and SC carriers was compared,and the operating parameters of sludge in situ biofilm system were optimized.The experimental results showed that the optimal operating conditions of biofilm system were operating temperature at 25°C,HRT 12h and DO concentration 4⁵ mg/L;the _FSCSBBR constructed with FSC carrier had better performance of sludge in situ reduction than _SCSBBR sludge.The Y_obsbs was 0.22±0.10 g MLSS/g COD,which reduced sludge production by 27.27%.The average removal rates of pollutants?COD,NH4+-N,TN,and TP?were 93.39%,96.66%,82.13%,and 60.23%,respectively,and 5.22%,1.43%,6.57%,and 7.47%higher than those of _SCSBBR.The biofilm system with FSC has better effect on the sludge in situ reduction and pollutant removal.The potential mechanism of sludge in situ reduction in SBBR reactors with different carriers was analyzed and discussed in depth.The test results showed that the sludge decay and metabolism uncoupling were the main cause of sludge in situ reduction.The sludge reduction induced by sludge decay in _FSCSBBR is 33.18%higher than that in _SCSBBR,and metabolic uncoupling reduced sludge in _FSCSBBR is 80%higher than _SCSBBR.Bacteroidetes and Acidobacteria were dominant phylum microbes in the two sludge reduction systems.Fimuricutes related to hydrolytic fermentation,microorganisms such as Spirochaete and Mizugakiibacter were enriched on the surface of FSC biofilms and their relative abundance was greater than SC.Fermentation bacteria promote biofilm hydrolysis,and lysis-cryptic growth was also the sludge in suit mechanism in _FSCSBBR.The optimal conditions and operating efficiency of phosphorus removal in A²O-SIC was explored.The results showed that the optimum operating conditions of the phosphorus removal unit were as follows:the pH of the crystallization column mixture was 8;the reaction time was 30 min;the seed particle size was 100¹50 mesh;the aeration volume was 300 L/h;and the Ca/P was 2.5;seed dosage was 50%;anaerobic supernatant flow rate was 40%.The average effluent concentration of TP was 0.54 mg·L^-1with the removal rate 88.89%,and the Y_obsbs of A²O-SIC was 0.18±0.05 g MLSSS/g COD.The addition of SIC unit will not deteriorate the microbial activity of mainstream A²O,but it can promote the enrichment of specific microorganisms related to phosphorus removal reaction such as Thauera,Methyloversatilis,etc.,and increase the content of PAO.The coupling effect can effectively increase the EPS content of mainstream units,reduce sludge production,provide additional carbon source,and increase the efficiency of combined process nitrogen and phosphorus removal.