Determination of the optimal operational parameters for a three-phase fluidised bed bioreactor with a light biomass support when used in treatment of phenolic wastewaters

The operational parameters, namely: the ratio of bed (settled) volume to bioreactor volume (V-b/V-R), the air velocity a and residence time t, for which the largest COD removals from phenolic wastewater were achieved, were determined for a three-phase (gas-liquid-solid) fluidised bed bioreactor with KMT(R) (Kaldnes Miljotechnologi AS) particles (made of polypropylene) used as biomass support. It was found that the largest COD removals were obtained when a bioreactor was operated at the ratio (V-b/V-R) = 0.55, the air velocity u = 0.041 m/s and residence time t = 45 h. Therefore, these values of (V-b/V-R), u and t can be considered as the optimal operational parameters for the bioreactor with KMT(R) particles when used in treatment of phenolic wastewaters. A decrease in COD from 53,400 to 950 mg/l was obtained, that is, approximately a 98% COD reduction was achieved. The pH was controlled in the range 6.5-7.0 and the temperature was maintained at 28-30 degreesC. The biomass loading in a bioreactor depended on the ratio (V-b/V-R) and the air velocity u. In the cultures conducted after change in (V-b/V-R) at a set u, the constant mass of cells grown on the support media was achieved after approximately a 6-day operation. With change in a at a set (V-b/V-R), the new steady-state biomass loading occurred after the culturing for about 3 days. (C) 2004 Published by Elsevier B.V.