ANAEROBIC BIODEGRADATION OF GASOLINE OXYGENATES IN SOILS

This study evaluated the biodegradation of methyl tertiary butyl ether (MTBE), ethyl tertiary butyl ether (ETBE), and tertiary butyl alcohol (TBA)-three chemicals used as gasoline additives. The biodegradation under sulfate reducing, methanogenic and denitrifying conditions was measured in static soil and water microcosms using soils of different origin and varying characteristics. The results indicate that TBA was the easiest compound to biodegrade, whereas MTBE was the most recalcitrant. It is thought that cleavage of the ether bond in MTBE and ETBE is the first and rate-limiting step in the degradation of these organics. TBA degradation was enhanced by nutrient addition in the nutrient poor soils but hindered by the presence of other easily-degraded organic compounds. Degradation of MTBE and ETBE occurred only in the soil with the lowest organic matter content and with a pH around 5.5. No degradation of MTBE and ETBE was observed in the organic-rich soils, and in the organically poor soil the addition of easily degradable organic compounds inhibited MTBE and ETBE degradation.