Methyl tert-butyl ether (MTBE) bioremediation studies

The massive production of methyl tert-butyl ether (MTBE), a primary constituent of reformulated gasoline, combined with its mobility, persistence and toxicity, makes it an important pollutant. It was considered recalcitrant until a few years ago, but recently MTBE biodegradation in aerobic conditions has been demonstrated with both mixed and pure cultures. Mixed cultures are generally the more effective for MTBE removal, and the addition of a suitable co-substrate to the cultures can enhance the removal. The slow degradation of MTBE has been observed under anaerobic conditions, but only in the presence of humic substances. In recent work, degradation possibilities have been demonstrated when MTBE is the sole carbon and energy source, although the biodegradation was slow. In several cases the addition of a co-substrate such as n-alkane, particularly pentane, improved MTBE degradation. The biological treatment of MTBE contaminated soil, water and groundwater could provide a simpler, less expensive alternative to chemical and physical processes for MTBE removal, and the possibility of such an approach has led to investigations into the microbial consortia able to degrade this compound, and the best environmental conditions for its removal. Over the last few years the state of the art of MTBE bioremediation studies has expanded rapidly and numerous articles have been published. Field experiments have revealed the possibility of removing MTBE completely, though the process is slow. Particularly important are treatments involving biostimulation, diffusing oxygen in contaminated groundwaters, and bioaugmentation, that has been demonstrated to improve MTBE removal. The aim of this paper has been to provide a summary of the literature available on MTBE biodegradation in batch systems, reactors and in field.