Removal of nitrogenous and carbonaceous substances by a porous carrier-membrane hybrid process for wastewater treatment

Porous carriers in fluidized bed have been used for microbial immobilization in order to simultaneously remove organic carbon and nitrogen in wastewater. In particular, multifunctional microbial reactions in the carrier, such as simultaneous nitrification/denitrification, play important roles in nitrogen removal. To enhance these reactions the substrates should be supplied into the carrier with appropriate rates. This is because the denitrification reaction was often limited by the supply of organic substances, due to overgrowth of heterotrophs in the region near the carrier surface. A porous carrier-membrane hybrid process was found to have improved nitrogen removal efficiency, due to stimulated denitrification as well as nitrification. The hybrid system achieved a 30% higher nitrogen removal ratio than that in the fluidized porous carrier system. Microelectrode studies revealed that although intracarrier denitrification rate in a conventional fluidized bed was limited by organic carbon, this limitation was reduced in the hybrid process, resulting in the increased intracarrier denitrification rate. These effects were due to suppressed glucose oxidation in aerobic region in the hybrid process. (C) 2002 Elsevier Science B.V. All rights reserved.