Formation Of Aerobic Granules Biodegrading Methyl Tert-Butyl Ether And Microbial Community Analysis

Floccular activated sludge was used as the seeding sludge, Methyl tert-butyl ether (MTBE) as a target pollutant, and ethanol as a co-substrate in this study. Aerobic granular sludge was cultivated in a sequencing batch reactor (SBR) through regulating the operation parameters. The seeding sludge had an average diameter of 77.5μm, with SVI 428mL/g and MLVSS 1060mg/L, while the matures aerobic granular sludge is 0.5mm, 41.39mL/g and 4000mg/L respectively. After the granulation, the influent concentration of MTBE increased to 400mg/L, while the effluent were consistently below 5mg/L, and the removal efficiencies of MTBE were above 95%. The batch experiments showed that there was a good fit between the biodegradation date and the Michaelis-Menten equation. (R~2=0.929). The highest MTBE biodegradation rate was up to 20.9 mg-MTBE/(g-VSS·h). SEM observation indicates that the mature granules consisted of a wide variety of bacteria, including rods-like, cocci-like and filamentous bacteria.PCR-DGGE analysis indicated that microbial population differed obviously during the aerobic degradation. Most bands in the seed sludge disappeared and some new bands appeared in the aerobic granules degrading MTBE, which related to the changes of microbial species, especially correlated with the development of MTBE-degrading microbes. The fingerprints of PCR-DGGE indicated that aerobic granules had rich microbial population and stable community structure, implying little variation about the composition and diversity of microorganisms during the stable operation period. The sequencing results showed that the dominant organisms responsible for MTBE degradation closely related to Flavobacteria,α-proteobacteria,δ-proteohacteria,β-proteobacteria,γ-proteobacteria, Ciliophora, and Bacteroidetes.The batch experimental results showed that MTBE-degrading aerobic granules exhibited the capability for biodegrading the co-contaminants, TBA and BTEX. BTEX biodegradation by the aerobic granules was much faster than MTBE or TBA. However, there exisited a short adaptation period when the substrates were changed from MTBE to BTEX. The presence of TBA had no apparent negative effect on the biodegradation of MTBE, while the presence of the BTEX mixtures would produce an obvious negative effect on the MTBE biodegradation. The DGGE profiles of the microbial communities showed that there were no obvious changes in bacterial flora after degrading TBA, whereas an obvious microbial shift could be observed after degrading BTEX.