| With the rapid development of our economy and modern industry,the production and consumptions of various chemical products are increasing,thus leading to the discharge of a large amout of industrial wastewater.Industrial wastewater usually exhibits high toxicity,high organic content and low biodegradability,and the development of highly efficient process is thus urgently needed.In this thesis,anaerobic membrane bioreactor(AnMBR)and upflow anaerobic sludge blanket(UASB)reactor,were used for anaerobic treatment of two typical industriual wastewater,i.e.methanolic and petrochemical wastewater.The objectives of this thesis were to explore the feasibility of anaerobic biological treatment of high-concentration industrial wastewater to recover bio-energy and possible metabolic mechanism,hoping to provide basic data and practical guidance for real-world anaerobic treatment of industrial wastewater.The main conclusions are as follows:(1)A lab-scale submerged anaerobic membrane bioreactor(AnMBR)was operated to investigate anaerobic methane conversion and metabolic mechanism of methanolic wastewater at various organic loading rates.The bioreactor showed desirable performance with the chemical oxygen demand removal(COD)efficiency of up to 89.8 ± 1.1% and the highest methane production rate of 5.49 L/L-reactor/d.However,due to gradual decreases in the particle size and increased extracellular polymeric substances(EPS),membrane fouling gradually appeared and increased over time.The main contribution to membrane fouling originated from the cake layer formation,accounting for 97.4-99.1% of total membrane resistance.Further observations in the shifts of microbial community structure in response to organic loading rates indicated that Methanomethylovorans(67.03%)is the largest methanogen,followed by Methanosaeta(4.54%),Methnobacterium(1.55%)and Methanolina(1.23%)and the main bioconversion pathway of methanolic wastewater to methane in AnMBR system was methylotrophic methanogenesis,followed by acetotrophic/hydrogenotrophic processes.(2)A lab-scale upflow anaerobic sludge blanket(UASB)reactor was operated to investigate the anaerobic methane conversion and microbial community response of petrochemical wastewater at various hydraulic retention time(HRTs)and wastewater compositions.The optimal HRT was 18 h with OLR 7.50 g COD/L d and four petrochemical wastewater mixes which included polyvinyl alcohol(PVA 0.092),ethylene glycol(EO 0.092),purified terephthalic acid(PTA 0.728),polyester(PET 0.087)wastewater,which gained 84.2% methane content and the highest biogas and methane production rate of 0.72 ± 0.25 L/L-reactor/d and 0.54 ± 0.29 L/L-reactor/d,respectively.Further observations of high-throughput sequencing technology presented the OLR and wastewater composition significantly affected the microbial community structure.The acid-alkali and nitrile-containing wastewater was more toxic,which reduced the abundance of microorganisms related to methanogenesis by anaerobic fermentation and then resluted in a reduction in methane production.(3)A lab-scale hollow fiber anaerobic membrane bioreactor(HF-AnMBR)was operated to investigate the anaerobic methane conversion and microbial community succession of petrochemical wastewater at different hydraulic retention time(HRTs)and wastewater compositions.The optimal HRT was 18 h with OLR 7.50 g COD/L d and four petrochemical wastewater mixes which included polyvinyl alcohol(PVA 0.092),ethylene glycol(EO 0.092),purified terephthalic acid(PTA 0.728),polyester(PET 0.087)wastewater,which gained 83.2% methane content and the highest biogas and methane production rate of 1.01 ± 0.13 L/L-reactor/d and 0.84 ± 0.12 L/L-reactor/d,respectively.Further observations of high-throughput sequencing technology indicated the OLR and wastewater composition had significant effect on the microbial community structure.The acid-alkali and nitrile-containing wastewater was more toxic,which reduced the abundance of microorganisms related to methanogenesis by anaerobic fermentation and then resluted in a reduction in methane production.In addition,with the gradual operation,the trans-membrane pressure(TMP)gradually increased to 26.4 kPa,and membrane fouling gradually appeared and became serious.Organic pore blocking was the most contribution of membrane fouling,accounting for 62.1% of the total membrane resistance,followed by the cake layer formation.The gradual increase of TMP attributed to the increase of OLR,the different compositions of petrochemical wastewater and the gradual increase of sludge concentrations in the reactor.(4)The addition of nano zero valent iron(nZVI)in the anaerobic digestion system is an effective technology to improve the degradation efficiency and methane production of purified terephthalic acid(PTA)wastewater.The highest cumulative methane production of 364.8 mL/ g COD and methane content of 90.2% was obtained with nZVI 0.5 g/g VS by the end of anaerobic operation,which increased by 16.6% and 42.5% respectively relative to the nZVI 0 g/g VS.nZVI could be used as an electron donor source for anaerobic digestion,stimulating the synthesis of key enzymes related to methanogenesis,changing the structure of microbial communities with increasing abundance and agglomeration of symbiotic bacteria(Syntrophus,Syntrophorhabdus and Syntrophobacter)and methanogens(hydrogenotrophic methanogenesis(Methanobacterium)),increasing further methane production.However,it was worth noting that the higher dosage of the nZVI(0.75 and 1.0 g/g VS)damaged the microbial cell structure,causing a decrease in the activity and relative abundance of the microorganisms and inhibition of methane production.The research would provide theoretical basis and technical supports for improving the treatment efficiency and energy recovery of anaerobic bio-technology treating PTA wastewater. |
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