Physical and chemical properties of MTBE make it a challenge to deal with effectively. Unlike most gasoline constituents, MTBE is highly soluble in water, 20 times more than BTEX. It also partitions strongly from air to water, and it is much less likely than benzene to adsorb to soil or organic carbon.
After a petroleum release, MTBE can reach the groundwater and dissolve rapidly. Once here, MTBE travels at about the same rate as the groundwater whereas benzene and other petroleum constituents tend to biodegrade and adsorb to soil particles.
Contaminated water sources 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 Italian concentration limit fixed by the law for MTBE is 40 µg/l in groundwater, 10 mg/Kg dw soil in residential areas and 250 mg/Kg dw soil in industrial areas (D.M n.31/2015).
Biosearch Ambiente has developed an in situ bioremediation system capable of removing this pollutant from vast areas.
TREATMENT APPROACH
Biosearch Ambiente has developed an in situ bioremediation system that exploits the natural biodegradation process operated by naturally occurring bacteria living in the contaminated environment.
In situ MTBE biodegradation has been widely reported. Indigenous microorganisms 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).
To accelerate the rate of microbially mediated degradation reactions and stimulate the activity of microorganisms by optimizing environmental conditions, it is necessary the implementation of an engineered system, which involves the in situ delivery of chemicals to stimulate biological activity. For this purpose we prepare a balanced nutrient mixture, whose composition is determined through laboratory test.
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. It is also essential to monitor the physicochemical 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 TBA.
Microorganisms in the matrix utilize MTBE as carbon and energy source
In situ injection of nutrient mix into the subsurface to stimulate indigenous MTBE-degrading bacteria.
Groundwater and soil
Months
MISE, MISO, Full scale remediation
