Treatment of recalcitrant wastewaters in traditional suspended growth systems is ineffective due to the required large contact times and large aeration basins. Hollow-fiber gas permeable membranes are being investigated as a novel approach to overcome oxygen and 2,4,6-trinitrophenol (TNP) mass transfer limitations of conventional fixed film systems. Three independent hollow fiber biofilm reactors using bubbleless membrane aeration technology were used to treat TNP. The reactors contained 14, 30, or 57 fibers, with a fiber spacing of 3, 2.7, or 2.1 mm, respectively, which resulted in a packing factor of 0.5%, 1% and 2%. A pure culture of Nocardioides simplex (strain Nb), which has been shown to mineralize TNP, was immobilized on the surface of 281.5 (m outer diameter microporous fibers. Pure oxygen was supplied through the lumen of the fibers and diffused throughout the biofilm and into the reactor. Removal of TNP in the 14, 30, and 57 fiber reactors was 99.1, 83.2, and 85.4%, respectively at a contact time of approximately 14 hours and a TNP loading of 40 mg/day. Results indicate TNP diffusion into the biofilm limited performance at high substrate concentrations.

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