Prof. Christof Holliger, Dr. Ricardo Cespedes, Chantal Seignez
July 2000 – June 2002
Dr. J.R. van der Meer, EAWAG; Dr. D. Pieper, GBF, Braunschweig, Germany; Prof. W. Reineke, BUGHW, Wuppertal, Germany
The major goal of this project was to characterize the composition and dynamics of the bacterial consortium present in the biotrickling filter system treating chlorobenzene-containing waste gas in order to establish the optimal operation conditions for the inoculum production and the operation of the biotrickling filter itself. More specifically, the objectives were
- to determine the composition of the bacterial consortia of the inoculum-producing bioreactor and the biotrickling filter,
- to isolate chlorobenzene-degrading bacteria from the consortia and determine their physiological and biochemical properties, their phylogenetic affiliation as well as their contribution to the total biomass and the degradation activity, and
- to analyze the dynamics and stability of these populations under different operation conditions
An artificial waste gas contaminated with chlorobenzenes was treated by using the degradation capacity of a microbial community immobilized on a carrier material in a laboratory-scale biotrickling filter. The inoculum was produced in a fed-batch bioreactor. With an organic load of 2 kgC/m3 d and a retention time of 1,9 min, a removal efficiency of 85% was achieved. The microbial community growing on the solid support was investigated by FISH, TGGE/DGGE and T-RFLP analyses. The composition of the community over the height of the biotrickling filter was very homogeneous. The community was dominated by β-proteobacteria in the fed-batch bioreactor and the biotrickling filter. The species involved, however, seemed not to be the same. In contrast, the composition of the α-proteobacteria, a minority group, was extremely stable in both systems. The detailed analysis of the microbial communities obtained in the inoculum-producing bioreactor or the biotrickling filter with either ammonium or nitrate as nitrogen source showed that the microbial communities of the biotrickling filter were different from the bioreactor communities. This indicated that the inoculum produced in the bioreactor was for the major part composed of bacteria not relevant finally in the biofilm of waste gas-treating biotrickling filter.