We developed and used steady-state permeation tests and a mathematical model to determine the H-2 permeabilities of three hollow fibers (composite, polyester, and polypropylene) commonly used in the H-2-based membrane biofilm reactor (MBfR). The H-2 permeabilities spanned a wide range: 1.6 x 10(-6), 1.8 x 10(-7), and 6.6 x 10(-8) m(3) H-2 @ standard temperature and pressure m membrane thickness/m(2) hollow fiber surface area d bar for the composite, polypropylene, and polyester hollow fibers, respectively; this represents a ratio of the maximum H-2 flux for composite:polypropylene:polyester hollow fibers = 32:3.3:1. The H-2 permeabilities were then used to correlate hollow-fiber type to contaminant-removal flux in previous MBfR experiments. Only the experiments with composite hollow fibers were not routinely limited by H-2 delivery, although fouling by mineral precipitates lowered the H-2 flux in some cases. Since existing contaminant-removal data for the polyester hollow fibers were not adequate, we did special experiments to investigate the effect of H-2 pressure on contaminant removal in the MBfR with the polyester hollow fibers. We confirmed that this hollow fiber was operated at its maximum H-2-delivery capacity based on its H-2 permeability. (C) 2012 Elsevier B.V. All rights reserved.