| With the purpose of improving efficiency of wastewater biological nitrogen removal,urban wastewater treatment plants(WWTPs)are moving towards the direction of high efficiency,intelligence and resource recovery in the new round of upgrading and transformation.The oxygen uptake rate(OUR),active biomass(X_A,X_H)and yield coefficient(Y_H)are important biomass activity parameters that determining microbial performance and reflect the operating efficiency of the system.Aiming at monitoring,control and rapid response to abnormality wastewater of wastewater biological treatment,two integrated fixed-film activated sludge(IFAS)system were studied,under different influent conditions and external carbon source addition dosing.The distribution of the amount of active biomass,biomass activity and heterotrophic bacteria yield coefficients with different types of biomass were investigated with seasonal succession.In addition,the effects of external carbon source conditions on the microbial nitrification,denitrification efficiency and biomass activity parameters of activated sludge in the IFAS system were explored.Moreover,from the perspective of microbial community,the correlation between it and biomass activity parameters was established,which analyzed the macroscopic change law of complex microbial community structure,and provided a basis for modeling and precise control of IFAS system.The main results of this study were as follows:(1)Based on two groups of full-scale IFAS systems with different influent substrate conditions and with or without external carbon source feeding systems,the total active biomass in the activated sludge in each chamber of system I and II systems were 59.97～68.41,71.72～86.30 g COD/g MLSS.In the suspended bio-carriers in the aerobic chambers,the total active biomass was 0.51±0.06 and 0.69±0.04 g COD/m~2,respectively.In summer and autumn,the total active biomass of different biomasses generally increased significantly in autumn.The growth ratio of the active autotrophic biomass(X_A)was higher than that of the active heterotrophic biomass(X_H)in autumn,and the proportion of X_A in suspended bio-carriers(No.Ⅰ:47%,No.Ⅱ:55%)was higher than that in activated sludge.In addition,the proportion of X_H in No.Ⅱsystem was higher than that of No.Ⅰsystem.Influent substrate conditions,external carbon source addition and seasonal succession all affected the distribution and proportion of active biomass.(2)The results of the changes of specific respiration rate(SOUR)and Y_H of biomass in each chamber of the two full-scale IFAS systems with seasonal succession showed that the SOUR of microorganisms in different biomass in autumn was lower in autumn than in summer,while the Y_H was higher in autumn than in summer.The decreased of endogenous specific respiration rate(SOUR_E)and the increased of Y_Hensure the growth of biomass in autumn,which made up for the decline of microbial activity per unit mass biomass at the same time.The different effects of seasonal succession on the amount and activity of biomass worked together to remove pollutants and ensure that the effluent meets standards.(3)In view of the demand for additional carbon sources for biological denitrification of wastewater,the research based on the influence of external carbon source factors on microbial efficiency and activity parameters shows that excessive carbon dosing can cause a reduction in carbon source utilization,with Y_H=0.7548 at an external carbon source of 100 mg/L and a carbon source utilization of only 25%.After the organic load impact of OLR-1,OLR-2,OLR-3,OLR-4,OLR-5,the ammonia oxidation rate of nitrifying microorganisms decreased,the nitrification reaction was incomplete,and the all Y_H value to over 0.75 g COD/g.The denitrification rates were9.75,4.11,3.43,5.27,8.74 and 11.02 mg/(L·h)for sodium acetate,glucose,methanol,ethanol,sodium propionate and primary sludge fermentation liquor as external carbon sources,respectively,with Y_H values of 0.76,0.43,0.52,0.59,0.66 and 0.70 g COD/g.According to the above research results,considering the active microbial biomass and activity to select the appropriate external carbon source in different seasons,which not only ensures the efficiency but also reduces the sludge yield.(4)Studies based on microbial community structure showed that the microbial communities in the reaction zones of full-scale IFAS systems evolved seasonally.The enrichment of Firmicutes and SBR1031 spp.is also more likely in systems with an external carbon source,which is associated with sodium acetate as an external carbon source.In addition,the genera Nitrospira and Nitrosomonas were much higher on suspended biocarriers in IFAS systems than in activated sludge.(5)The studies based on the correlation between microbial community structure and biomass activity parameters showed that there was a significant correlation between them in the full-scale IFAS system.The genera of JG30-KF-CM45,Anaeromyxobacter,Trichococcus had extremely strong correlations with biomass activity parameters;the genera of Candidatus＿Microthrix,Saccharimonadales,Microtrichales were positively correlated with X_A,X_H,and negatively correlated with SOUR_E,SOUR_A,SOUR_H,and the positive and negative correlation did not change with the season.Correlations of biomass activity parameters with the genus Gemmatimonadaceae weakened in autumn;while those with genera SC-I-84,Romboutsia,and f＿＿67-14 strengthened.Different genera showed seasonality in the correlation with activity parameters,and the seasonality of the correlation between the same genus and microbial activity parameters in different systems was also different.This study analyzed the evolution of the biomass activity parameters of the full-scale IFAS system under different influent substrates,external carbon sources and seasonal conditions.And from the perspective of saving energy consumption of external carbon source and reducing sludge yield of wastewater treatment system,the strategy of selecting the optimal external carbon source scheme according to the amount and activity of active biomass in different seasons was proposed.In addition,a bridge between microscopic microbial communities and macroscopic activity parameters was built,which can realize real-time visualization of microbial communities.The above research results provided practical theoretical and technical support for the efficient,intelligent and resource-based development of wastewater treatment system in our country. |
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