EVALUATION OF PULSED FEEDING STRATEGIES FOR THE COMETABOLIC IN SITU BIOREMEDIATION OF MTBE
Abstract:Pulsed feeding strategies for a primary growth substrate can be used during in situ bioremediation to minimize competitive inhibition during cometabolic biodegradation of MTBE. Four different feeding strategies of isopropanol (IPA) were investigated to stimulate the biodegradation of MTBE by the propane-oxidizing bacterial strain ENV425 (Envirogen, Inc.): (a) continuous, (b) long pulse duration/low frequency, (c) short pulse duration/high frequency, and (d) short pulse duration/low frequency. The experiments were carried out in a series of inoculated aerobic sand columns (50-cm long, 2.5 cm diameter) containing coarse-grain silica sand and supplied continuously with a buffered feed solution (pH 7) containing nutrients, 0.5 mg/L MTBE, and 100 mg/L hydrogen peroxide. Each experimental treatment received an approximately equivalent mass input of IPA over a 6-day period. Continuous and short pulse duration/high frequency feeding strategies led to non-detectable levels of MTBE (< 0.004 mg/L) in the effluent pore water. Low frequency pulse feeding strategies led to occasional MTBE breakthrough in the effluent pore water with a maximum MTBE concentration of 0.23 to 0.31 mg/L. MTBE breakthrough time at the conclusion of the experiment, after IPA addition was stopped, provided an additional assessment of the capacity of the sand column biomass to remove MTBE. In the treatment utilizing a continuous feeding strategy, MTBE was detected in the effluent pore water after 1.2 pore volumes while all pulsed fed treatments experienced initial MTBE breakthrough at 2.0 to 2.5 pore volumes. The results of this study show that careful consideration needs to be given to the timing and the concentration of primary substrate feed pulses when devising a feed strategy, and that a short pulse duration/high frequency feeding strategy appeared to be the most promising approach for the stimulation of MTBE biodegradation by propane-oxidizing bacteria.
Document Type: Research Article
Publication date: 2002-01-01
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