Investigation on performance of a three-phase fluidized bed bioreactor with a novel biomass support in treatment of industrial wastewaters

Aerobic biodegradation of a petroleum refinery and a brewery wastewater has been carried out in a pilot-scale bioreactor with a novel biomass support (KMTR*). The principle features of the biomass support, which was made of polyethylene, were its low density (930 kg/m' ), interstice structure, high surface area to volume ratio for microbial attachment and high interparticle collision. The high interparticle collision prevented microbial over growing on the surface of the particle. A study was made on the principal operating parameters that influenced the biodegradation of the petroleum and brewery wastewaters in the 110-litre three phase fluidised bed bioreactor which was operated batchwise. An orifice gas distributor was used. The operating parameters like superficial gas and liquid velocities, aspect ratio and phase hold-ups were optimised. Investigation of the bioreactor performance was done primarily from hydrodynamics point of view. Comparing the gas hold-ups for brewery wastewater, petroleum wastewater and tap water, it was found that gas hold-up in brewery wastewater was highest followed by that of tap water. Method of measuring sludge turbidity with a spectrophotometer method was employed in order to determine the microbial concentration in the reactor. Operating at ambient conditions the optimum operating gas superficial velocity and aspect ratio were found to be 2.7 cm/s and 10 respectively. Employment of the novel biomass support made it possible to attain fluidisation both at low superficial gas anti liquid velocities and improved microbial attachment due to large surface area created by the interstice structure. Treatment of mixed petroleum and brewery wastewater showed better results than the treatment of either petroleum wastewater brewery wastewater alone it was therefore concluded that combined treatment may be applied in industrial wastewater treatment.