| MBR-ASSR process is the improvement of OSA process, which was the common process in order to sludge reduction of Wastewater Treatment Plant. The paper mainly investigated the effect of different side-stream ratio(SR) on the performance of pollutant removal, sludge reduction and membrane fouling, and the migration and transformation of dissolved organic matter was researched by Three-dimensional excitation-emission matrix(3D-EEM) fluorescence spectroscopy and gel permeation chromatography(GPC) etc. Furthermore, microbial community of aeration tank, ASSR and membrane surface of MBR-ASSR process were analyzed, for the purpose of studying the effect of SR on the diversity and structure of microbial populations.Both MBR-ASSR and controlled MBR process have reached satisfactory COD and NH3-N removal efficiency, which can reach 82% and 95%, respectively. TN removal efficiency was relatively low, however, the removal rates increased with the increase of SR from 20% to 100%. The measure of ORP and p H explained that ASSR module could provide stable anoxic or anaerobic circumstances and denitrification conditions. In the all systems, when the SR were 0%, 20%, 50% and 100%, the Yobs were 0.1353, 0.1272, 0.1126 and 0.068kgss/kg COD, the SR was bigger, the Yobs is lower. Compared to the controlled process, the sludge reduction efficiency were 5.99%、16.77% and 49.74%,respectively.ASSR module contains sludge lysis, the release of nitrogenous substances, denitrification and others phenomenon. With the increase of SR, the concentration of TN and NOx--N of sludge supernatant from the effluent of ASSR were increased, whereas NH3-N showed the opposite tendency. When passed through anoxic and aerobic tank, organic matter was decomposed and used, the concentration of COD and protein decreased, nevertheless, the concentration of COD and protein were raised for the sludge lysis after anaerobic tank. And the higher SR, the change of concentration was smaller. Calculating the second substrate release of ASSR module under different SR circumstance, we could find that SCOD were 3084.26, 4348.54 and 5230.16mg/d, respectively, when the SR was 20%, 50% and 100%. The SR was much higher; the concentration of organic matter was more in per unit time.GPC analysis showed that macromolecular substance gradually disappeared after anoxic tank, which was degraded into micromolecular substance, owning to sludge lysis, there were the release of macromolecular substance in the ASSR module, and distribution of molecular weight was broader distribution with the SR increased. According to 3D-EEM analysis, there were three fluorescence peaks, which were tryptophan, humic and fulvic-like substances, respectively. Among them tryptophan-like substance varied most significantly in ASSR module, the intensities decreased with increasing of SR, the next was humic-like substance, the intensities of fulvic-like substances was unchanged basically.Both Sludge settlement and extracellular polymeric substances(EPS) properties are the major factors caused membrane fouling. The results showed that when SVI>150m L/g, the membrane fouling rate was the four times of that SVI<150m L/g, explaining that sludge settlement deteriorated for the sludge recycle from ASSR, which would in turn accelerated the rise of TMP. Slime-EPS and LB-EPS were observed to have stronger potential of membrane fouling, and protein showed more significant correlations than polysaccharose with membrane fouling. In addition, EPSp/EPSc had the positive relationship of membrane fouling, whereas TB-EPS/LB-EPS had the negative relationship of membrane fouling. In the ASSR module, protein was mainly existed in TB-EPS, protein of LB-EPS and TB-EPS was increased with the increase of SR, Slime-EPS showed the opposite regulation, however, the change was not obvious. Furthermore, the proportion of TOC, protein and polysaccharose in Slime, LB and TB-EPS were increased with the increase of SR, and protein was the main substance on the membrane surface.Analyzing the fluorescence character of EPS by 3d EMM showed that EPS of sludge and membrane surface contained three components. The C1(tryptophan-like) and C3 components(humic-like) were most existed in TB-EPS, the intensity of C1 increased in aerobic tank.The insert of ASSR would change the distribution of microbial communities, and create the advantageous environment of microbial growth for sludge reduction. In ASSR module, the relative abundance the anaerobic bacteria(Chloroflexi 、 Acidobacteria 、 Chlorobi 、 Verrucomicrobia and WCHB1-60) of DOM degradation was higher, the relative abuance of Acidobacteria and Anaerolineae were much higher when SR increased. SR also affected the microbial communities, among them the change of Chlamydiae was the most obvious. The relative abundance of microbial communities, which were related to sludge reduction, were investigated in ASSR module and was higher than that in controlled MBR. The relative abundance of AOB increased with the increase of SR, whereas NOB showed no change. Denitratisoma, belong to denitrifying bacteria, increased with the increased of SR. |
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