MEMBRANE DELIVERY OF HYDROGEN FOR AUTOTROPHIC DENITRIFICATION

This research focused on the novel use of hollow fiber membrane modules for gas delivery in biological denitrification using hydrogen-oxidizing bacteria. Autotrophic denitrification is a biological process that reduces nitrate to nitrogen gas using an inorganic carbon source. Hydrogen gas is an electron donor and nitrate is the electron acceptor in the reaction. The specific research objectives were to evaluate the hydrogen transfer characteristics of hollow fiber membrane modules, and assess technical feasibility of a continuous bioreactor-membrane system for denitrification.This research focused on the novel use of hollow fiber membrane modules for gas delivery in biological denitrification using hydrogen-oxidizing bacteria. Autotrophic denitrification is a biological process that reduces nitrate to nitrogen gas using an inorganic carbon source. Hydrogen gas is an electron donor and nitrate is the electron acceptor in the reaction. The specific research objectives were to evaluate the hydrogen transfer characteristics of hollow fiber membrane modules, and assess technical feasibility of a continuous bioreactor-membrane system for denitrification.Laboratory scale mass transfer tests were conducted using hollow fiber membrane modules and the following mass transfer correlation was developed to design membrane modules for hydrogen dissolution into water:where, Sh is the Sherwood number, Re is the Reynolds number, de is the equivalent diameter of the membrane module, L is the length of the fibers and Sc is the Schmidt Number.Continuous flow studies indicated that a stable biofilm can be developed in a packed bed reactor to remove nitrate using hydrogen as the electron donor. Hydrogen gas was successfully delivered to the reactor via the hollow fiber membrane gas transfer module without fouling. Dissolved hydrogen concentrations indicate that the system did not experience hydrogen limitations at detention times of 3.25 hours or greater. Membrane gas delivery appears to be a viable technology for transferring hydrogen to water for autotrophic denitrificiation.