MTBE (Methyl Tert-Butyl Ether) is a synthetic organic compound used as gasoline additive to raise fuel oxygen content; it has been developed to replace tetraethyl lead, used until the ‘70s. MTBE is highly water soluble and persistent in the environment: when introduced in proximity of an aquifer, it can diffuse and travel long distances. Contaminated water sources can become undrinkable and MTBE can even enter the food chain. In addition to MTBE, its natural, toxic metabolite TBA (Tert-Butyl Alcohol) can also contaminate the environment. The concentration limit fixed by the law for MTBE in groundwater is 10 µg/l.
Biosearch Ambiente has developed a remediation system capable of removing this pollutant from vast areas.
Biosearch Ambiente has developed an in situ remediation system that exploits the natural biodegradation process operated by bacteria living in the contaminated matrix.
MTBE biodegradation in the environment has been widely reported. Microorganisms indigenous to the matrix utilize MTBE as carbon and energy source, both in aerobic and anaerobic conditions. In the former case oxygen is the final electron acceptor, while in the latter case the acceptor can be nitrate, Mn (IV) or Fe (III).
However, for the process to proceed at a significant speed, it is necessary to stimulate the relevant bacteria population to grow; for this purpose we prepare a balanced nutrient mixture, the composition of which is determined with growth experiments in the laboratory. It is also essential to monitor the physico-chemical conditions in the matrix during the remediation process, in order to adjust the composition of the nutrient mix and avoid the formation of toxic metabolites such as TBE.
The remediation approach is thus fine-tuned according to the aquifer characteristics and the contaminant levels. The nutrient mixture is injected in the groundwater using specially designed injection wells.