HOLLOW FIBER MEMBRANE BIOREACTOR FOR NITRIC OXIDE REMOVAL

摘要

This research evaluates the use of a Hollow Fiber Membrane Bioreactor (HFMB) to remove Nitric Oxide (NO) from combustion gases. In the HFMB, waste gases pass through the lumen of microporous hydrophobic hollow fiber membranes. The pollutants diffuse through membrane pores to an attached biofilm where they are biodegraded. The membranes serve as a support for the microorganisms and provide a large surface area for gas transfer. In this project, nitrifying bacteria were enriched from activated sludge with a liquid NH_4~+/NO_2~- feed. After acclimation, an NO/air mixture was introduced to the HFMB at varying liquid velocities. A maximum removal efficiency of 74% was attained at a liquid velocity of 1.5 cm s~(-1). The effects of gas composition and temperature on mass transfer and biodegradation were investigated using a synthetic combustion gas (15% CO_2, 5% O_2, 75% N_2, 100 ppm NO) at temperatures between 20°C and 55°C. NO removal efficiency was maintained at approximately 70% regardless of gas composition or temperature. Only nine to twelve percent of the eliminated nitrogen was recovered as nitrate nitrogen in the effluent. This may have been due to concurrent nitrification/denitrification.