| The high-saline wastewater is characterized by not only numerous sources but also annual incremental discharge,which is urgent for the development of cost-effective treatment solutions.Salt-tolerant Aerobic Granular Sludge(SAGS)technology is considered as a promising and alternative solution in the field of high-saline wastewater biological treatment due to its higher biomass concentration,excellent solid-liquid separation,strong resistance of salinity loading and abundant functional community.However,the development and engineering application of SAGS process remained issues because of the overlong start-up time of SAGS process,the restricted methods of granulation reinforcement as well as the inefficiency of continuous-flow real-world high-saline wastewater treatment.Based on the key influencing factors of AGS formation,it is proposed that the formation of SAGS was reinforced by the combination of hydraulic,biological and environmental selective pressure.To solve above problems,this dissertation firstly developed the rapid granulation of activated sludge and elucidated the phase-related characteristics and the microbial community succession.Secondly,it revealed the microbial mechanism of granulation reinforcement as means of intertidal sludge as Exogenous Additives.Thirdly,it clarified that the effect of operation mode and configuration on the hydraulic characteristics,SAGS formation and microbial characteristics.Finally,it developed the catalytic ozonation coupled with SAGS process for the treatment of actual reverse osmosis concentrate(ROC)and achieved the pilot scale demonstration.Above results could provide theoretical basis and technical parameters in developing the systematic techniques for SAGS cultivation,strengthening the performance of high-saline wastewater treatment systems and promoting near-zero discharge of actual high-saline wastewater.The main conclusions were summarized as follows:(1)The rapid granulation of activated sludge was achieved and the phase-related characteristics and the microbial community evolvement were elucidated.To solve the problem of long-term development of SAGS process,the rapid granulation of activated sludge was achieved within 11 d with the granular mean size of 0.9 mm by the onestep means of anchoring the critical settling velocity(CSV)at 2.4 m·h-1.The rapid granulation process was characterized into selective adaptation phase,growth transition phase and stable phase.Metagenomics revealed that Mangrovibacter was the dominant colonizing consortia in adaptation phase,which might be related to the complete capsular polysaccharide anabolism pathways in the genome.The abundance of Mangrovibacter decreased to 4.2%from 74.9%while the Acidisoma-dominant genus rapidly increased with abundance of 79.4%in transition phase.The mutualistically interaction between filamentous-like fungi Geotrichum and Acidisoma-dominant consortia might play an important role in the rapid granulation of activated sludge.The high salt wastewater treatment of high-strength sulfate by the novel SAGS process results in overgrown filamentous granules and deteriorative sedimentation performance,but the removal efficiency of COD and total inorganic nitrogen increased by 8.4%and 76.1%.(2)the microbial mechanism of granulation reinforcement as means of intertidal sludge as Exogenous Additives were revealed.Compared with activated sludge,the exogenous additives can enhance the granulation of SAGS,in which the activated sludge mixed with intertidal sludge is the best chose,with a mean size of 1.3 mm,granulation speed increased by 46.1%,delay time decreased by 30.2%,SVI30 of 28.7 mL·g-1 and COD removal efficiency of 95.5%.After long-term operation,the problems of filamentous overgrowth and unstable particle structure could be fundamentally solved.Compared with activated sludge,the activated sludge mixed with intertidal sludge resulted in a nearly 5-fold increase in extracellular PN component content of SAGS,in which tryptophan and tyrosine protein was the key component.Moreover,the limit of salt tolerance was up to 70 g TDS·L-1 and the maximum specific sludge activity was 14.4 g·g VSS-1·d-1.The reason for the granulation reinforced by activated sludge mixed with intertidal sludge is that Rhodobacteraceae,Marinicella are the key hosts of tryptophan and tyrosine protein synthesis gene(trpBD,tyrBC).Besides,the reason for the specific activity and the salt tolerance limit promoted by activated sludge mixed with intertidal sludge is that the genus Rhodobacteraceae,Marinicella become the dominant carriers of genes encoding betaine synthetase(betB,gbsA)and ion transportase(nhaH,trkA).(3)The effect of operation mode and configuration on the hydraulic characteristics,SAGS formation and microbial characteristics were clarified.For the same operation mode,the improvement of equipment configuration helps to promote the cultivation of SAGS.By improving the operation mode and configuration,the continuous flow airlift internal circulation reactor(CFAIR)can further enhance the granulation process with the granulated time of about 13 days,the maximum mean size of 1.8 mm,sludge concentration of 6.1 g·L-1,SVI30 of 17.3 mL·g-1 and COD removal efficiency of 94.0%.The computational fluid dynamics analysis showed that average liquid velocity,vortex scale and maximum hydraulic shear rate were the key hydraulic factors in granulation process.For the same configuration,the enhancement effect of operation mode on SAGS cultivation process was not dependent on the increase of extracellular tryptophan and other PN content,but on the alternative feast and famine condition and the feast/famine ratio was reduced by 60%under continuous operation compared with the sequential batch mode.The typical operation mode of sequential batch and continuous had significant influence on the SAGS community structure.Bradymonadales was the dominant genus in sequential batch operation and Rhodobacteraceae was the dominant one in continuous operation.Compared with sequential batch operation,enhancing the transport of substrates such as amino acids to maintain energy supply or decreasing the growth rate to improve the aggregative performance under continuous operation may be an important way for SAGS community to respond to the lower feast/famine ratio,and ultimately strengthen the cultivation process of SAGS.(4)The performance and stability of catalytic ozonation coupled with SAGS process for the treatment of actual reverse osmosis concentrate(ROC)was investigated.The catalytic ozonation coupled with SAGS process for the treatment of actual reverse osmosis concentrate(ROC)was developed.In bench scale,the process parameters of catalytic oxidation were optimized with ozone influent concentration of 50 mg·L-1,ozone influent flow rate of 0.2 L·min-1,catalyst dosage of 50 g·L-1,initial pH of 8.42 and HRT of 60 min.The highest COD removal rate was 38.4%and BODs/COD increased from 0.01 to 0.21.The effluent COD concentration of catalytic oxidation coupled with SAGS system reached 42.0 mg·L-1,which met the DB31/199-2018 primary standard and the total COD removal efficiency reached 79.0%.In pilot-scale integrated catalytic oxidation and SAGS process,SAGS-CFAIR could be achieved the effluent COD concentration of 77.5 mg·L-1 and the total COD removal rate of 64.8%under the wastewater conditions of low COD concentration,high salinity and low temperature and operations of shortening HRT.The results showed that the different experiment scale significantly affected the succession of SAGS microbial community and temperature and influent TDS concentration were the main environmental factors affecting the SAGS community structure.Catalytic ozonation is mainly responsible for the break of organic ester bonds or the shortening of alkane carbon chains,while SAGS process is mainly responsible for the final mineralization of intermediate products such as phthalates. |
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