抄録
Effects of upflow velocity on the biofilm physical properties in items of biofilm thickness, biofilm density and biomass per unit surface area of support particles were investigated by using lab-scale anaerobic fluidized bed reactors fed with a synthetic wastewater (a mixture of skimmilk and sucrose ; 2,000 mg-COD·l-1). Four identical reactors were operated for a period of 100 days in parallel at different upflow velocities, i. e., 4, 7, 14 and 25m·hr-1. The initial biofilm formation process was categorized into three types.
For the runs at 14 and 25m·hr-1, direct adhesion of inoculum sludge onto the carrier surface took place promptly, and the biofilm thickness developed up to 200 μm within only 1 to 2 days, and then decreased eventually to 100 μm. On the contrary the biofilm density increased consistently up to 10.2 mg·cm-3 and 4.4, respectively.
As for the run at 7m·hr-1, the biofilm thickness increased gradually to 100 μm with an increase in the biofilm density up to 14.4mg·cm-3. Granulated sludge in the size ranging 1 to 5mm and containing several carriers was formed at the lowest upflow velocity of 4m·hr-1.
The occurrence of initial adhesion led to shorten the period for which the biomass per unit surface attained the saturation values. The biofilm density was a more useful factor to determine the biomass per unit surface.
