Sunday, July 29, 2007
P53

Acrylonitrile Biofiltration by Rhodococcus rhodochrous DAP 96622 in a Trickling Bed Bioreactor: Bioavailability Studies and Three-Dimensional Distribution of Biofilm Accessed by Scanning Confocal Laser Microscopy

Jie Zhang and George E. Pierce. Department of Biology, Georgia State University, 24 Peachtree Center Ave, Atlanta, GA 30303

Acrylonitrile(AN) is  a major volatile waste generated in acrylamide production industry. A trickling bed bioreactor was developed for biofiltration of AN, with Rhodococcus rhodochrous DAP 96622 supported on a granular activated carbon (GAC) column. The performance of the biofilm reactor was evaluated during both batch and open modes of operation. GAC biofilm in batch system supplied with 180-3600ppm AN (10.8-216 mg AN g-1 GAC) suggested that except for the lowest concentraion of AN supplied (180ppm), a residual fraction of AN (up to 56%) remained absorbed to the GAC and therefore was biologically unavailable. For the batch-open switch mode, low efficiency of the reactor reflected the adsorption of AN to GAC, which was subsequently degraded after the system was returned to single-pass open mode. When AN inlet concentration was 500mg l-1 and retention time was 8.5min during open mode, about 35% of AN was removed. Samlpes were taken from different sections of the carbon column and the three dimensional structure of the biofilm stained with acridine orange was visulized by scanning confocal laser microscopy. It revealed a very robust and heterogenerous biofilm, with microcolonies interspersed with voids and channels. Precise measurements of biofilm characteristics by a computer program, COMSTAT, agreed with the assumption that the biomass and thickness of the biofilm increased along the carbon column depth.

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