Bioremediation of MTBE: a review from a practical perspective

The addition of methyl tert-butyl ether (MTBE) to gasoline has resulted in public uncertainty regarding the continued reliance on biological processes for gasoline remediation. Despite this concern, researchers have shown tha t MTBE can be effectively degraded in the laboratory under aerobic conditio ns using pure and mixed cultures with half-lives ranging from 0.04 to 29 da ys. Ex-situ aerobic fixed-film and aerobic suspended growth bioreactor stud ies have demonstrated decreases in MTBE concentrations of 83% and 96% with hydraulic residence times of 0.3 hrs and 3 days, respectively. In microcosm and field studies, aerobic biodegradation half-lives range from 2 to 693 d ays. These half-lives have been shown to decrease with increasing dissolved oxygen concentrations and, in some cases, with the addition of exogenous M TBE-degraders. MTBE concentrations have also been observed to decrease unde r anaerobic conditions; however, these rates are not as well defined. Sever al detailed field case studies describing the use of ex-situ reactors, natu ral attenuation, and bioaugmentation are presented in this paper and demons trate the potential for successful remediation of MTBE-contaminated aquifer s. In conclusion, a substantial amount of literature is available which dem onstrates that the in-situ biodegradation of MTBE is contingent on achievin g aerobic conditions in the contaminated aquifer.