Synergistic Degradation Of Phenolic Compounds By Microorganisms/Biogenic Manganese Oxides

Phenol is a typical environmental pollutant,which widely exists in industrial wastewater.The removal of phenolic pollutants by using physical,chemical and biological methods has been widely studied.A moving bed biofilm reactor(MBBR)was used to treat simulated phenol wastewater with acidic shock(pH 7.5–3.0)and determine phenol and COD removal rate.In the pH shock phase,the phenol and COD removal efficiencies initially decreased and gradually increased to more than 90%.Microscopic studies showed that the superficial biofilm was mainly composed of fungi(yeasts)in the acidic pH shock phase.The microbial community composition in the acidic pH shock phase was significantly different from those in other phases.Firmicutes and Ascomycota were the dominant bacterial and fungal phyla in this stage,respectively.16 S rRNA gene-based functional annotation indicated that functional profiles related to aromatic compound degradation existed in all of the stages.Therefore,MBBRs show potential for the treatment of phenolic wastewater exposed to pH shock.Subsequently,in order to further enhance removal performance of phenol pollutants,the microorganism/biogenic manganese oxides(BioMnOx)combined treatment system was established by enriching manganese oxidizing bacteria(MnOB)in MBBR.Mn(II)added into simulated phenol wastewater can be oxidized to manganese oxide in situ by microorganisms after 90 days' operation.Then,4-chlorophenol(4-CP)was added into MBBR to simulate a mixed phenolic wastewater.Comparing with the MBBR(R1)without feeding Mn(II),the MBBR with BioMnOx production(R2)exhibited robust phenol and 4-CP removal performance during further 148 days' operation to overcome the phenol/4-CP concentration and hydraulic retention time(HRT)fluctuations.16 S rRNA gene sequencing was employed to decipher the microbial community.Proteobacteria is account for more than 50% of the bacterial community in all of the phases,and several putative MnOBs was identified at specific phases of R2(Pseudomonas?Cupriavidus and Spirosoma).On the other hand,the batch experiment demonstrated that partly purified BioMnOx does not exhibits phenol remove capacity,but can remove 4-CP efficiently.Interestingly,5-cholro-2-hydroxymuconic semialdehyde was found in the products of 4-CP degradation,suggesting a novel catechol 2,3-dioxygenase(C23O)-like activity of BioMnOx,indicating the existence of BioMnOx provides an alternative pathway besides the microbial driven 4-CP degradation.Overall,a MBBR based MnOB enrichment under high phenol concentration was achieved,and the 4-CP/phenol removal can be accelerated by in-situ formed BioMnOx.Considering the C23O-like activity of BioMnOx,the results of this study proved the possibility that a combined system involving nanomaterials and microbial communities could degrade organic pollutants synergistically.