Membrane processes and surfactant-enhanced subsurface remediation: resultsof a field demonstration

This paper documents the importance of membrane processes to surfactant-enh anced subsurface remediation and presents results of a field study on these processes. Surfactants enhanced the contaminant (BTEX) concentrations by o ne to two orders of magnitude over baseline ground water concentrations. Th e surfactant stream was decontaminated by air stripping in hollow fiber mem branes and concentrated using ultrafiltration. Hollow fiber air stripping w as able to avoid foaming problems which will be more common in packed tower air strippers. A 10000 MWCO ultrafilter was able to recover a majority of the surfactant (approaching 80%) despite being hindered by ground water dil ution (ground water extraction was four times greater than injection to mai ntain hydraulic control). A fundamental model of surfactant-reduced strippi ng efficiency was corroborated by the field results, providing further conf idence in the use of this model for design purposes. The high level of surf actant recovery (90%+/-6%) achieved in a relatively low permeability format ion (1 ft/day or 3.5x10(-4) cm/s) is also encouraging. These results thus d emonstrate the importance of an integrated design to optimize system perfor mance, and illustrate the ability of surfactant-enhanced technologies to ex pedite subsurface remediation. (C) 1998 Elsevier Science B.V. All rights re served.