Effects of components of multiples emulsions system in the MTBE contaminants by microbial consortium

Abstract

The use of water-in-oil-in-water (W1/O/W2) emulsions has been proposed in environmental studies for treating water systems polluted with contaminants in low concentrations, where other treating techniques are not effective. For example it has been proposed that a microbial consortium capable of degrading methyl tert-butil ether (MTBE) be entrapped in a W1/O/W2 emulsion for treating water contaminated with MTBE. However a proper selection of the materials (emulsifying agents, oil phase) making up the W1/O/W2 emulsion must be carried out in order to ensure that the microbial consortium does not consume these materials, interfering with the degradation of MTBE. The objective of this study was to determine the consumption of potential materials for making up the W1/O/W2 multiple emulsions, in the presence and absence of MTBE, by the microbial consortium. Potential materials proposed for making up the multiple emulsions W1/O/W2 are Span 80 as the primary lipophilic emulsifier, mesquite gum (Prosopis laevigata) and polyacrylic acid as the secondary hydrophilic emulsifiers, and light mineral oil as the intermediate oil phase. Each of these compounds was used by separate at a concentration of 0.2 % in microcosms with and without MTBE. Production of CO2 was quantified as a measure of the compounds consumption. In the absence of MTBE, results indicate that Span 80 was used as carbon source by the microbial consortium, showing significantly higher (P<0.05) production of CO2 than that observed for mesquite gum and mineral oil. CO2 production was non-significantly (P>0.05) different when MTBE was present with Span 80 than when it was not, but was significantly higher (P<0.05) CO2 production when it was incorporated to mesquite gum or polyacrylic acid than when it was not. Thus, the use of Span 80 in the formulation of W1/O/W2 multiple emulsions entrapping a microbial  onsortium for degrading MTBE is not recommended, as Span 80 is consumed by the microbial consortium, and it inhibits the consumption of MTBE.