From microorganisms to engineered systems: A laboratory study on the bioremediation of MTBE-contaminated groundwater.

摘要

Methyl tert-butyl ether (MTBE) and its daughter product, tert-butyl alcohol (TBA) are gasoline additives and groundwater pollutants of increasing concern. The frequent occurrences of MTBE and TBA causing nuisance in groundwater require an efficient, but also environmentally friendly treatment. Therefore, bioremediation of MTBE and TBA contaminated groundwater has been the subject of this research.; Microbiological studies presented herein have been focused on a MTBE degrading bacterial consortium. PCR-DGGE (Polymerase chain reaction and denaturing gradient gel electrophoresis) analyses of ribosomal DNA were used to investigate the microbial community and revealed more than seven predominant bacterial members. Most of isolates were found not capable of degrading MTBE, but two of them, Cons 2A and Cons 2B, showed the same effectiveness in eliminating MTBE as the consortium. The subsequent phylogenetic analysis revealed that it is very likely they are strains of Rubrivivax sp., variants of PM1, a known MTBE degrader.; Three types of laboratory scale engineered systems were constructed, namely, biotrickling filter, in situ biotrickling filter, and in situ biobarrier. Detailed experiments were conducted to examine the performance and limits of these reactors. The results suggest that the bioreactors are robust even at low temperatures, if allowed sufficient dissolved oxygen to ensure aerobic conditions. The presence of co-contaminants, BTEX (benzene, toluene, ethylbenzene, and xylene) inhibited the MTBE biodegradation to different degrees, but none of these compounds completely repressed MTBE biodegradation. The consortium showed good capability to remove BTEX and TBA, or were able to completely remove TBA at a faster rate than MTBE when it was present alone.; A dynamic model for describing both steady state and transient-state behavior of the bench-scale biotrickling filter for TBA/MTBE removal was also developed. Experiments were carried out with TBA, and the data generally agreed with the model. The transient behavior during air shutdown and re-start experiment was accurately predicted by the model. The model provides numerical means to simulate and explore the biodegradation phenomena, which could be fully explored in designing full size reactors.; Overall, the methods and technologies presented here can be good candidates for bioremediation of MTBE, TBA and possibly other pollutants in groundwater.