| In recent years,the pharmaceutical industry has developed increasely in China.A large amount of pharmaceutical wastewater is characterized by complex components,high content of inorganic and organic compounds,and refractory to biodegradation.Therefore,it is great significant to develop an efficient and stable technology for treatment of pharmaceutical wastewater.Membrane bioreactor(MBR)is a combination of traditional biological treatment and modern membrane separation.It has been applied extensively in the field of municipal wastewater and industrial wastewater treatment in recent years,because it has the advantages of high product water quality and excellent sludge retention ability.However,there are still some problems such as high energy consumption and serious membrane fouling.In this thesis,the aerobic MBR(AeMBR)and anaerobic MBR(AnMBR)were built to treat low-concentration pharmaceutical wastewater.In order to compare the performance and membrane fouling characteristics in this two MBR systems,scanning electron microscopy with energy dispersive X-ray(SEM-EDX),three-dimensional fluorescence spectroscopy(3D-EEM)and gel permeation chromatography(GPC)were applied.Furthermore,the enhanced AnMBR system with addition of biochar was developed to treat high-concentration pharmaceutical wastewater,because the AnMBR has advantages of excellent performances of pollutants removal and energy recovery.For the sake of understanding the mechanism of pharmaceutical wastewater treatment process,the performance of enhanced AnMBR systems,characteristics of anaerobic membrane fouling,component of membrane foulants,and microbial community structure in anaerobic sludge were investigated,using the technologies of atomic force microscope(AFM),fourier transform infrared spectroscopy(FTIR)and high-throughput sequencing.The major results are as follows:1.The pollutants removal performance,characteristics of membrane fouling and composition of membrane foulants of AeMBR and AnMBR were studied.The results showed that AnMBR had relatively high potential in pharmaceutical wastewater treatment.When the hydraulic retention time(HRT)was 24 hours and organic loading rate(OLR)increased from 0.5 kg COD/(m3 d)to 1.2 kg COD/(m3·d),the chemical oxygen demand(COD)and absorbable organic halogen(AOX)removal efficiency of AnMBR were 95.3±2.0%and 54.7±6.4%,respectively,and the mixed liquor volatile suspended solids(MLVSS)of AnMBR was higher.Meanwhile,the extracellular polymeric substances(EPS)content in membrane foulants was far lower,and the cake layer was loose and porous,resulting in an average growth rate of transmembrane pressure difference(TMP)of 0.3 kPa/d,which was lower than that in AeMBR of 0.675 kPa/d.Further analysis of EPS content of membrane foulants in AeMBR and AnMBR showed that tryptophan protein and aromatic protein might be the key factor for membrane fouling.Compared with AeMBR,the average molecular weight of protein in AnMBR was smaller(27607 Da),which had less tendency to cause the blockage of membrane pores and accumulation on the membrane surface.However,the accumulation of inorganic pollutants on the membrane surface of AnMBR was more than that of AeMBR,and the humic acid was found only on the membrane of AnMBR.2.The effect of biochar particles on pollutants removal,sludge biomass,gas production and composition in AnMBRs for treatment of the high-concentration pharmaceutical wastewater were studied.The results showed that when HRT was 24 hours and OLR increased from 1.5 kg COD/(m3 d)to 7.0 kg COD/(m3 d),the removal efficiencies of COD,total nitrogen(TN)and AOX in AnMBR-2(with addition of biochar)were 93.8±1.7%,44.1±2.5%and 61.5±9.0%respectively,which were higher than 89.2±2.2%,37.1±4.4%and 56.2±7.1%in control group(AnMBR-1).At the same time,no acidification occurred in both AnMBRs.Compared with AnMBR-1,the oxidation-reduction potential(ORP)and effluent volatile fatty acids(VFAs)in the AnMBR-2 were lower,and the MLVSS increased to 20.3±1.3 g/L.Moreover,the gas production and its methane proportion were 1.4±0.2 L/(L·d)and 68.2±2.7%,respectively.3.The effect of biochar addition on membrane fouling characteristics and membrane foulants composition of AnMBRs was studied.The results showed that the average growth rate of TMP in AnMBR-2 was 0.26 kPa/d,lower than that of AnMBR-1(0.38 kPa/d),and the roughness of membrane surface in AnMBR-2 was reduced obviously.The addition of biochar reduced the proportion of Al,Si,Ca and Fe on membrane surface,and the molecular weight of protein was further reduced(67.71%of small molecular proteins in 0.1-0.15 kDa).Furthermore,humic acids content in membrame fouling was reduced significantly with biochar added.It was speculated that the addition of biochar effectively reduced the dissolved microbial products(SMP)content in the supernatant of AnMBR-2(72-82%of SMP content in AnMBR-1),and the membrane fouling could be alleviated by controlling the properties of anaerobic mixture.The microbial communities in anaerobic sludge and membrane deposits were analyzed.Results showed that the microbial diversity and abundance in anaerobic sludge were significantly increased after biochar added.At the phylum level,Proteobacteria(33.3%),Bacteroidetes(19.8%)and Clerooflexi(4.7%)were the dominant microbes,and Rikenellaceae spp.(10.0%)and Thauera spp.(2.8%)were enriched at the genus level.These microbes had the ability to degrade fatty acids,halogenated organic compounds and aromatic organic compounds.For archaea,acetotrophic methanogens such as Methanosarcina spp.(17.8%)and Methanosaeta spp.(17.1%)were enriched.In the aspect of microorganism in membrane deposits,biochar inhibited the enrichment of Bacteroidetes and Firmicutes,which could easily cause membrane fouling.In summary,biochar particles favor the pollutants removal and sludge retention,and could improve the property of anaerobic mixture via adsorption,coring and regulating microbial community.The alleviation of membrane fouling could be realized effectively in AnMBR. |
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