Research On Performances For High Concentration Sulfate And Organic Wastewater Treatment In Anaerobic Processes And Microbial Community Structure And Function

The discharge of sulfate wastewater increased greatly with the rapid development of industries.The large amount high concentration sulfate organic wastewater could result in water acidification and inhibitory effects on aquatic organism when released into environmental water body.Moreover,the H2S produced under reducing condition could pollute the atmosphere.Biological methods especially the representative anaerobic-aerobic processes are widely applied to the treatment of industrial wastewater due to its lower cost,lower energy consumption,etc.However,high concentration sulfate has significant adverse effect on the operation of anaerobic process,and the composition of sulfate wastewater is really complicated with some macromolecule refractory toxic organic pollutants.Thus,it's very hard to steadily conduct anaerobic process to treat high concentration sulfate organic wastewater.In this study,the secondary generation(Up-flow anaerobic sludge bed reactor,UASB)and third generation(Expanded granular sludge bed reactor,EGSB)anaerobic bioreactors were applied to treat simulated high concentration sulfate wastewater.During this process,the operation parameters were optimized,and the effect of sulfate concentration on anaerobic systems was researched.The removal performance of sulfate and organic matters were improved by changing pH,adding Fe0 and Fe2O3.The effect of toxic pollutants on sulfate reduction process was also investigated.Meanwhile,the biotechnologies including conventional technique(real time PCR,q-PCR)as well as next generation sequencing technology(Mi-seq)were applied to analyze microbial community structure and abundance of functional genes in different phases of anaerobic systems.Based on these analyses,we combined the removal performances with microbial community,provided comprehensive insights into anaerobic process treating complex high concentration sulfate organic wastewater both from theoretical and practical angles.The main conclusions of this study are following:(1)EGSB and UASB reactors could start successfully with hydraulic retention time(HRT)at 36 hours,influent pH at 7.5±0.1,and temperature at 37+1?.EGSB reactor had relatively shorter start-up time and more steady operational performance compared with UASB reactor.The optimal operational parameters of EGSB reactor are HRT at 36-18 h,influent pH at 6.5-8.5,Recycle ratio at 20:1,un-flow velocity at 0.8925 m/h.The optimal operational parameters of UASB reactor are HRT at 36-24 h,influent pH at 7.5±0.1,un-flow velocity at 0.0425 m/h.Moreover,the microbial community structure during the start-up period in the EGSB reactor was stable,so the EGSB reactor possessed strong resistance to impact load.(2)EGSB reactor could treat wastewater containing 5400 mg/L SO42-under anaerobic condition and 10800?g/L SO42-under acidified condition,and tolerate the concentrations of S2-,H2S and VFA at 750 mg/L,750 mg/L and 9000 mg/L,respectively.UASB reactor could treat wastewater containing 4500 mg/L SO42-under anaerobic condition and 8100 mg/L SO42-under acidified condition,and tolerate the concentrations of S2-,H2S and VFA at 600 mg/L,600 mg/L and 8000 mg/L,respectively.The optimal removal efficiency of sulfate and COD were 70%and 88%,respectively,with the influent concentration of sulfate and COD were 3600 mg/L and 9000 mg/L,respectively.The absolute abundance of dsrA and mcrA genes was higher in EGSB reactor,consistent with powerful resistance to impact load and toxicity.Proteobacteria was the dominant phylum in EGSB,while Firmicutes in UASB reactor.Moreover,it was found more genera of SRB in EGSB who worked on sulfate reduction together.(3)The optimal dosage of FeO is 12.5-15 g,and with this dosage,the removal performance of COD and sulfate were increased by 40%and 50%,respectively,and the concentration of S2' and H2S was 77-92 and 222-374 mg/L,respectively,and the pH value increased from 3.0 to 6.1-6.5.The dosage of FeO improved the treating performance of high concentration sulfate organic wastewater under acidified condition,which might be related to the production of Fe2+.The optimal dosage of Fe2O3 is 15-20 g,and with this dosage,the removal performance of COD and sulfate were increased by 22%and 30%,respectively,and the concentration of S2-and H2S was 17-100 and 77-322 mg/L,respectively,and the pH value increased from 3.0 to 6.1-6.5.In addition,the optimal dosage of FeO and Fe2O3 lead to the highest concentration of EPS.The dosage of Fe2O3 resulted in increased polysaccharide content in EPS,which was in favor of protecting microbial cell and chelating metals.The Fe element could stimulate the growth of microorganisms and improve the absolute abundance of dsrA gene,and Firmicutes was the dominant phylum under FeO and Fe2O3 condition.Moreover,the sulfate reduction rate also could be increased by adjusting the influent pH value.The optimal influent pH value is 10±0.2,and the effluent pH value could be maintained at 7.05-7.72.When the pH value was beyond 8.0,the growth of SRB was inhibited,while MPB could be stable under pH value at 7.5-8.3.Moreover,under optimal pH value,the microbial community was shifted from bacteria working on hydrolytic acidification to anaerobic bacteria,and the absolute abundance of dsrA was not decreased,while the transform of responding enzymes was blocked.(4)When the influent NH4+ concentration was 1000-2000 mg/L,the microorganisms could applied NH4+ for growth and metabolism,and NH4+ as well as SO42-could be removed simultaneously by sulfate-based anaerobic ammonium oxidation bacteria,which enhanced the removal efficiency of NH4+ and SO42-.The inhibitory concentration of Aniline on sulfate reduction was 160 mg/L,while 80 mg/L on COD removal.The inhibitory concentration of nitrobenzene and ortho-nitrotoluene was similar,which was 100 mg/L and 120 mg/L,respectively.Based on the concentration and composition of EPS,the concentration of EPS increased with increasing nitrobenzene and ortho-nitrotoluene stress,indicating that microorganisms could protect the cells via secreting EPS to improve hydrophobicity.Furthermore,it was found that the abundance of Geobacter,Gpl,Ktedonobacter and Arthrobacter rised obviously with the increase of influent NH4+ concentration,indicating that these microorganism were the potential sulfate-based anaerobic ammonium oxidation bacteria.The accumulation of Desulfovibrio under the condition of increased nitrobenzene and ortho-nitrotoluene concentration suggested that it could tolerate the toxicity of nitrobenzene and ortho-nitrotoluene.Proteobacteria was resistant to nitrobenzene and Firmicutes was capable of tolerating the poisonousness of ortho-nitrotoluene.