EVALUATION OF PULSED FEEDING STRATEGIES FOR THE COMETABOLIC IN SITU BIOREMEDIATION OF MTBE

摘要

Pulsed feeding strategies for a primary growth substrate can be used during in siturnbioremediation to minimize competitive inhibition during cometabolic biodegradation of MTBE.rnFour different feeding strategies of isopropanol (IPA) were investigated to stimulate thernbiodegradation of MTBE by the propane-oxidizing bacterial strain ENV425 (Envirogen, Inc.):rn(a) continuous, (b) long pulse duration/low frequency, (c) short pulse duration/high frequency,rnand (d) short pulse duration/low frequency. The experiments were carried out in a series ofrninoculated aerobic sand columns (50-cm long, 2.5 cm diameter) containing coarse-grain silicarnsand and supplied continuously with a buffered feed solution (pH 7) containing nutrients, 0.5rnmg/L MTBE, and 100 mg/L hydrogen peroxide. Each experimental treatment received anrnapproximately equivalent mass input of IPA over a 6-day period. Continuous and short pulsernduration/high frequency feeding strategies led to non-detectable levels of MTBE (< 0.004 mg/L)rnin the effluent pore water. Low frequency pulse feeding strategies led to occasional MTBErnbreakthrough in the effluent pore water with a maximum MTBE concentration of 0.23 to 0.31rnmg/L. MTBE breakthrough time at the conclusion of the experiment, after IPA addition wasrnstopped, provided an additional assessment of the capacity of the sand column biomass tornremove MTBE. In the treatment utilizing a continuous feeding strategy, MTBE was detected inrnthe effluent pore water after 1.2 pore volumes while all pulsed fed treatments experienced initialrnMTBE breakthrough at 2.0 to 2.5 pore volumes. The results of this study show that carefulrnconsideration needs to be given to the timing and the concentration of primary substrate feedrnpulses when devising a feed strategy, and that a short pulse duration/high frequency feedingrnstrategy appeared to be the most promising approach for the stimulation of MTBErnbiodegradation by propane-oxidizing bacteria.