Biodegradation of polychlorinated biphenyls using biofilm grown with biphenyl as carbon source in fluidized bed reactor.

This study investigated the use of biofilms in the biodegradation of polychlorinated biphenyls. The biofilm used was developed on modified cement particles using mixed microbial culture isolated from PCB-contaminated soil. The biofilm formed was first acclimatized to PCBs by feeding the reactor alternately with biphenyl and PCBs. The acclimatized biofilm was tested on simulated PCB-contaminated water containing Aroclor 1260 by using a three-phase fluidized-bed reactor operated in batch mode. The initial batch run yielded 80+/-2.38% PCB removal from medium in one day and 91+/-1.34% in 5 days. The percent PCB removal gradually increased in the succeeding runs reaching 92+/-2.48% in one day and a steady state value of 95+/-2.01% in 5 days from batch eight onwards. PCB removal from the medium was highest during the first day reaching 80-92%. The sudden decrease in PCB concentration was attributed to an initial adsorption of the PCB on the biofilm and then the compound was degraded gradually. Yellow intermediates were observed as the pH of the medium decreased. These intermediate products were further metabolized as indicated by the disappearance of the yellow substance.