MtBE biodegradation in a gravity flow, high-biomass retaining bioreactor.

The aerobic biodegradation of methyl tert-butyl ether (MtBE), a widely used fuel oxygenate, was investigated using a pilot-scale biomass-retaining bioreactor called a Biomass Concentrator Reactor (BCR). The reactor was operated for a year at a flow rate of 2500 L/d on Cincinnati dechlorinated tap water and an influent MtBE concentration of 5 mg/L. Treatment efficiency of MtBE in the reactor during stable operations exceeded 99.9%. The upper 95% confidence levels of effluent MtBE concentrations and its degradation byproduct tert-butyl alcohol (TBA) were 2.9 and 0.9 microg/L, respectively, during these stable conditions. In addition, the effluent was found to be of better quality than the influent tap water as reflected by dissolved organic carbon analysis. Microbial community DNA profiling was carried out using denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction amplified 16s rDNA. The BCR was found to be inhabited by a wide spectrum of bacterial species, most notably microorganisms related to the genera Hydrogenophaga, Methylobacterium, Sphingomonas, and Pseudomonas. These organisms were previously reported to be associated with MtBE degradation. With the contamination of groundwater by MtBE being a wide-ranging problem throughout the United States, it is essential to develop a technology capable of effectively remediating such aquifers in order to protect public health and the environment. The BCR's simple operation and low maintenance requirements may render it an economically attractive approach to remediating groundwater contaminated with MtBE.