Abstract
Microporous gas-permeable membranes are being investigated as a means to provide in situ delivery of hydrogen to contaminated groundwater to stimulate the biodegradation of chlorinated solvents. Because of the potential for sulfate reducing biofilms to form on the membrane and indirectly produce iron sulfides at the membrane surface, the effects of biological fouling and inorganic fouling on gas transfer performance were evaluated. In general, the gas transfer coefficient decreased as the quantity of foulant accumulated on the membranes increased. Despite the accumulation of a thick (up to 100 μ m) foulant layer comprised of micro-organisms and iron sulfide minerals, gas delivery continued under the conditions tested [Reynolds numbers (Re) from 650 to 5460]. More importantly, gas transfer would not have been significantly impeded by these foulants at typical groundwater velocities (Re from 4 × 10-4 to 4 × 10-3) due to the dominance of the liquid film resistance under those conditions. Therefore, gas-permeable membranes should be able to provide sustained gas delivery to groundwater, even in a fouling environment.
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