An investigation of the cometabolic degradation of thiophene in the presenc
e of benzene has been performed in a continuous biofilm system in order to
study the kinetics of this conversion. The study showed result that thiophe
ne interferes with the metabolism of benzene: benzene is not completely min
eralised in the presence of thiophene. The micro-organisms are inactivated
by thiophene, its metabolites or the metabolites of benzene. For low ratios
of thiophene to benzene in the inlet of the reactor, the bacteria seem to
adapt to thiophene and regain part of their activity that was lost when thi
ophene was introduced in the system. A hypothesis for this phenomena is tha
t toxic metabolites of thiophene are converted biologically or abiotically
into compounds, which are less harmful and inhibiting to the micro-organism
s. Resting cells, which have been activated previously with benzene, are ab
le to degrade thiophene, and this conversion leads to the inactivation or t
he death of the cells.