ENRICHMENT OF MICROBIAL POPULATIONS IN THE PROCESS OF BIOFILM FORMATIONIN ANAEROBIC FLUIDIZED BED REACTOR

Abstract

The changes in biofilm physical properties and microbial activities with respectto acid production, acetate production, methane productions from H₂ and from acetate, wereinvestigated during initial biofilm formation in anaerobic fluidized bed reactor, at fourdifferent upflow velocities, i. e., 4, 7, 14 and 25 m·hr^-1. An initial biofilm formationdue to the direct adhesion of inoculum sludge onto the carrier surface occerred significantlywithin 1 to 2 days in runs at 14 and 25 m·hr^-1 and the biofilm thickness developed up to 200pm. Succeedingly to the initial adhesion, the biofilm thickness decreased eventually to100 μm with time, while the biofilm density increased gradually to 120 and 60 mg·cm^-3, forrespective runs. For a run at 4 m·hr^-1, the whole bed was occupied by granulated sludge, having a size ranging 1 to 5 mm and containing several carriers. The microbial activitiesfor all four items increased rapidly to 5 to 30 times those of inoculum sludge in all runs.When the larger upflow velocity was imposed, the more quickly those activities attained atthe respective saturation values. The biofilm activities, excluding in the item of acidproduction, rose up to 5 to 7 times as large as those sludge grown in a suspended system.