A fluidized bed reactor with polyvinyl alcohol (PVA) gel beads as a biomass carrier was used for the degradation of p-nitrophenol (PNP) in an artificial wastewater. PNP (200 mg·l-1) was completely degraded at a hydraulic retention time (HRT) of 6 hours in the presence of 10 mg·l-1 glucose. However, PNP degradation became unstable at 250 mg·l-1 PNP and did not recover, which suggests that the decrease in the activity of PNP-degrading bacteria is due to the presence of glucose. On the other hand, when only PNP was supplied to the reactor, PNP (360 mg·l-1) was almost completely degraded at an HRT of 6 hours, and the PNP removal rates per volume and total solids (TS) were determined as 54 mg·l-1·h-1 and 12.6 mg·g-1·h-1, respectively. From the PCR-DGGE result, two bacterial DNA sequences similar to those of Acidovorax and Arthrobacter, which are known for their PNP degrading ability, were determined in the biomass attached to the PVA gel beads; thus, we conclude that these bacteria mainly contribute to the PNP-degrading activity in the reactor.
