Enhanced Biodegradation Methods And Mechanisms Of Typical Cyclic Organic Pollutants In Chemical Wastewater

Due to highly stability,recalcitrant and toxicogical nature of cyclic organic pollutants(nitrogen heterocyclic compounds,halogenated aromatic compounds and antibiotic etc.)in chemical industry wastewater,the conventional biological treatment technology is difficult to effectively treat them.The development of cost-effective enhanced biodegradation technology is of great significance for the treatment of refractory organic pollutants.In this study,in view of the lack of active microbial sources in the biological treatment system of nitrogen heterocyclic compounds such as pyridine,a continuous flow aerobic self-forming dynamic membrane bioreactor was developed to enhanced degradation of high strength pyridine wastewater by adding pyridine specific degrading bacteria.Enhanced anoxic biodegradation of pyridine coupled to nitrification in an inner loop anoxic/oxic-dynamic membrane bioreactor(A/O-DMBR).Aiming at the problem of low efficiency of electron transfer,Enhanced 4-chlorophenol biodegradation through the integration of Fe₂O₃ nanoparticles into an anaerobic reactor,long-term performance and underlying mechanism were studied.The lack of electron acceptor during biodegradation of antibiotics pollutants,enhanced photocatalysis-assisted biodegradation of tetracycline(TC)through nitrate was developed.New method was provided for the enhanced biological treatment of refractory organic pollutants.For the treatment of high-strength pyridine containing wastewater,a bioaugmented continuous-flow self-forming dynamic membrane bioreactor(CSFDMBR),which was consisted of a continuous flow airlift reactor(CFAR)and a dynamic membrane bioreactor(DMBR),was developed in this study.The results indicated that through the bioaugmentation by Rhizobium sp.NJUST18,CSFDMBR could be successfully started,which was confirmed by complete removal of pyridine,efficient nitrification and significant increase of biomass.Pyridine could be effectively degraded in the CSFDMBR even at influent pyridine loading rate as high as 9.0 kg m^-3 d^-1,probably due to the efficient biomass retention in the CSFDMBR,which could be attributed to the formation of aerobic granules and the key role of dynamic membrane.CSFDMBR presented good polishing performance in treating pyridine wastewater,with effluent total organic carbon(TOC)and turbidity as low as 22.5±6.8 mg L^-1 and 3.8±0.5NTU,respectively.Membrane fouling could be effectively controlled,as indicated by backwash period as long as 60 d.The observed efficient performance highlights the potential for the full-scale application of the bioaugmented CSFDMBR,particularly for highly recalcitrant pollutant removal.Enhanced biodegradation of high-strength pyridine was successfully achieved in the inner loop anoxic/oxic-dynamic membrane bioreactor(A/O-DMBR)in this study.Due to the key role of dynamic membrane in biomass retention,NH₄⁺released from pyridine biodegradation could be effectively nitrified to NO₃^-in oxic zone,which was then recirculated into the anoxic zone to serve as electron acceptor for pyridine biodegradation.Acetate dosage adversely affected pyridine biodegradation,due to the competitive effect of acetate towards NO₃^-.Increase of recirculation ratio positively affected pyridine biodegradation,due to high availability of NO₃^-at high recirculation ratio.At influent pyridine concentration as high as 1500 mg L^-1,effluent turbidity was well maintained below 10 NTU,indicating excellent biomass retention performance of the dynamic membrane.Microbial community analysis confirmed the enrichment of specific functional species in both anoxic and oxic zones.Stable performance during 260 days'operation confirmed the potential of A/O-DMBR for full-scale application.Fe₂O₃ nanoparticles coupled anaerobic system was provided for the degradation of highly recalcitrant and toxic 4-chlorophenol(4-CP)but lack of an integrative study.In this study,Fe₂O₃nanoparticles coupled anaerobic system was operated continuously for 250 d to elucidate technical feasibility,system stability,microbial biodiversity and underlying mechanism.The results showed that 4-CP and TOC removal efficiencies in the coupled UASB were always higher than 97%and 95%,verifying the long-term stability of Fe₂O₃ coupled UASB.As compared to the control UASB system,4-CP and TOC removal efficiencies in the coupled UASB increased by 42.9±0.4%and 27.5±0.7%.Microbial diversity in coupled UASB was higher than that in control reactor.Addition of Fe₂O₃ nanoparticles distinctly promoted the enrichment of species involved in dechlorination,fermentation,electron transfer and acetoclastic methanogenesis.The extracellular electron transfer ability,activity of the electron transport and conductivity of anerobic sludge were obviously enhanced with the addition of Fe₂O₃ nanoparticles,inducing enhanced 4-CP biodegradation performance.Due to the pivotal role of nitrate,enhanced photocatalysis-assisted biodegradation of tetracycline(TC)under anoxic system was realized through both and continuous experiments.In batch experiments,TC removal efficiency in photocatalytic assisted biodegradation with nitrate improved by more than 15%,compared to the photocatalytic assisted biodegradation without nitrate,which proved the technical feasibility of enhanced photocatalytic assisted biodegradation of TC through nitrate.The continuous flow photocatalytic coupled biofilm reactor(CFPCBR)was operated continuously for 165 d to investigate the performance of TC removal and mineralization.The TC and TOC removal efficiency of additional nitrate were maintained at 93.2±1.5%and 63.6±3.8%,respectively,which were significantly higher than those 51.3±2.8%and 47.6±6.7%in the photocatalytic assisted biodegradation system without nitrate.Nitrate as an electron acceptor significantly improved the removal efficiency of photocatalysis assisted biodegradation of TC.TC could be effectively decomposed to hypotoxicity intermediate products by photocatalytic,which was then effectively mineralized via respiratory metabolism of microorganism.TC was degraded via enhanced the synergy effect of photocatalysis and biofilms,which benefited both low toxicity of intermediate products and high activity of microorganism.Moreover,the specific functional species(Rhodopseudomonas,Thauera and Phreatobacter)were enriched to be involved in aromatic compounds and polyaromatic hydrocarbon through addition of nitrate.