Study On The Treatment Of Highly Toxic And Organic Industrial Wastewaters Using Membrane Aerated Biofilm Reactor (MABR) Technology

Membrane aeration biofilm reactor(MABR)system is an efficient wastewater treatment technology.Membranes in MABRs can serve as both a microporous aerator and biofilm carriers,making the biofilms as a type of counter-diffusion bioflm.Dissolved oxygen and contaminants gradient can be easily formed during this process,resulting in separate ecological niches for anaerobic and aerobic microorganisms in the bioflm.Therefore,MABR can enhance efficient removals of organic carbon and nitrogen pollutants.In this study,single and two-stage bench-scale MABRs were used to treat wastewater containing o-aminophenol(OAP)and mixed phenolic contaminants,respectively.The microbial diversity,structure and function of a bioflm exposed to different conditions were investigated by high-throughput 16S rRNA gene sequencing and metagenomics.The effects of operation and influent conditions on biofilms structure and function were evaluated through principal coordinates analysis,redundancy analysis,and Spearman correlation and so on.The potential degradation pathways were further estimated through the KEGG category "Xenobiotics Biodegradation and Metabolism."1)A two-stage bench-scale membrane-aerated biofilm reactor(MABR)was developed to treat OAP wastewater.Long-term process showed that MABR-1 can achieve the removal rates of 17.6 g OAP/m2 d and 29.4 g COD/m2 d.MABR-2 can effectively perform more than 90%TN removal with the addition of external glucose.Pseudomonas and Nitrosomonas were the key functional genera in MABR-1 and MABR-2,respectively.Functional genes related to OAP degradation,including amnA,B,D,dmpC,H,mhpD,E,F,and bphH,I,J,were detected,and the involved enzymes were predicted.The OAP-degrading species and functional contribution analysis indicated that OAP can be metabolized by a single Pseudomonas or by the synergistic effects of bacteria,mainly including Cupriavidus,Thauera,unclassified Sphingomonadaceae,Lysobacter,and Azotobacter or by the cooperation of all the bacteria above.These diversified patterns guaranteed the high efficiency for OAP removal in MABR when treating wastewater with high OAP concentration.2)A single membrane-aerated bioflm reactor(MABR)was used to treat wastewater containing phenol,p-nitrophenol and hydroquinone under increasing phenolic loading and salinity conditions.More than 95%of phenolic compounds were removed,and a removal efciency of 8.9 g/m2 d for total phenolic(TP)contents was achieved under conditions with 32 g/L of salt and 763 mg/L and 9.04 g/m2 d of influent TP contents.Salinity and specifc TP loading substantially affected the bacterial community.Gammaproteobacteria,Actinobacteria and Betaproteobacteria contributed more to initial phenolic compound degradation than other classes,with Pseudomonas and Rhodococcus as the main contributing genera.The key phenolic-degrading genes of different metabolic pathways were explored,and their relative abundance was strengthened with increasing phenolic loading and salinity.The diverse cooperation and competition patterns of these microorganisms further promoted the high removal efciency of multiple phenolic contaminants in the bioflms.These results demonstrate the feasibility of MABR for degrading multiple phenolic compounds in high saline wastewater.3)This study further explored the potential group sensing effect(QS)regulation system of MABR biofilm in phenolic wastewater,the mechanism was predicted according to the QS regulation system mediated by AHL and C-DI-GMP.The results showed that the relative abundance of genes related to the production of c-di-GMP increased with the increase of phenol load in both MABR systems,and these genes had the potential to indirectly promote the density of biofilm and phenol degradation ability.