Methyl tert-butyl ether (MTBE) elimination by cometabolism: laboratory and biofilter pilot-scale results

摘要

At the present, Mexico produces and imports MTBE to achieve its demands (9% in gasoline). Compared to other volatile organic compounds, there are relatively few studies on MTBE biodegradation. In general, MTBE biodegradation has been observed as cometabolism, although there are some reports of its biodegradation as the only carbon source. This work presents results of MTBE degradation by cometabolism with gasoline vapors and pure substances from laboratory experiments and with gasoline vapors from a pilot-scale biofilter. At lab oratory-scale, MTBE degradation rate was determined in microcosms using pure cultures and consortia. MTBE cometabolism in a pilot-scale biofilter was studied over a 260 day period. The pilot-scale biofilter was inoculated with a consortium previously adapted and fed with gasoline vapors for three months. MTBE degradation rate by cometabolism with pentane determined in microcosms was 0.017mg/h centre dot mg. Among the organic compounds tested, pentane was the best inductor for MTBE degradation. Cometabolism of MTBE with structurally simpler molecules such as pentane, diethyl ether and iso-butanol was observed but no degradation of tert-butyl alcohol, isoamyl alcohol and sec-butanol was observed with any of the inocula tested. Overall, higher cometabolic rates were observed using consortia as inocula versus pure cultures. The pilot-scale biofilter system treating gasoline vapors presented higher MTBE elimination capacities and total hydrocarbon elimination capacities than those reported 3.8 g MTBE/m~3/h and 16 g/m~3 h respectively. In addition, degradation of other compounds was determined. In general, linear alkanes and aromatics were rapidly degraded, while branched alkanes had lower removal efficiencies. Pilot-scale biofilter elimination capacities for hexane, iso-octane and toluene were 3.24 g hexane/m~3 /h; 3.13g iso-octane /m~3 /h, and; 1.49 g toluene /m~3 /h. Removal efficiencies for toluene were the highest and the most stable.