This paper presents the behaviour of selected. bacteria, the mixture of, an
d indigenous to municipal sewage microorganisms, in biodegradation of benze
ne, toluene, o-xylene and p-xylene (BTX). Apart from an expected different
behaviour under aerobic and anaerobic conditions the difference in degradat
ion rate obtained for the different microorganisms tested, suppositions on
practical application of the results were made. It was found that the mixtu
re of microorganisms present in municipal sewage can be advantageously used
in biodegradation of aromatic hydrocarbons under aerobic conditions. Oppos
ite conclusions could be drawn from the experiments performed in anaerobic
conditions where selected specific bacteria have been much more active. The
observations made, of toluene biosynthesis. under specific anaerobic condi
tions seem to be totally new and unique.