Book Description
Microporous flat-sheet and hollow-fiber membrane contactors were used to support air-liquid and liquid-liquid mass transfer interfaces. Modular contactors were used in a two-step process designed to transfer VOCs from a contaminated air stream, through a stripping fluid, to a degradative biofilm, where the compounds are effectively mineralized. The membrane contacting the contaminated air stream was coated on the air-contacting side with either PDD-TFE or plasma-polymerized silicone rubber. Contact times of VOC-laden air with membranes varied from 0.1-0.4 sec. VOC removal efficiencies ranged from 44 - 97%, depending primarily on air contact time. Octanol was used as the stripping fluid because of its low vapor pressure and water solubility, its high partitioning of VOCs from air, and its compatibility with bacterial growth. The concentration of VOC in the octanol strongly affects removal efficiency and transfer rate of VOCs into and out of the stripping fluid. Furthermore extraction of specific compounds from the air stream into octanol is unaffected by other VOCs in the air stream. The membrane-supported biofilm modules successfully removed VOCs from the recirculating octanol stream. Degradation of the aromatic compounds investigated (toluene, m-xylene) was achieved; these compounds were not observed in the aqueous phase above the biofilm. MEK biodegradation is problematic, appearing to be partially inhibited by toluene and m-xylene, and to be influenced by putative octanol degradation. Further mechanistic studies are required to ascertain the underlying mechanism.