whole bed height of a biofilter was divided into four individual reactor st
ages in series. This configuration permits a measurement of the leachate pH
of each stage individually and minimizes interstage mixing of the immobili
zed culture. The extent to which the residence time of pollutant in the fil
ter bed influenced biodegradation characteristics and the composition of im
mobilized culture under conditions of a constant loading rate was studied u
sing a perlite biofilter having an internal diameter of 50 mm and the bed h
eight of each stage being 27 cm. The residence time of pollutant in the bed
had no influence on the removal efficiency and the elimination capacity of
the whole biofilter although some changes of these parameters in the indiv
idual stages were observed. The biofilter achieved an elimination capacity
of 140 gm(-3) h(-1) at removal efficiencies greater than 90%. Degradation a
ctivity decreased the pH value of the leachate to 3.5-3.0. Microbial analys
es showed that styrene was degraded by eukaryotic cells at low pH values. A
t pH values above 4.0 prokaryotes were also present in the mixed culture.
(C) 2001 Society of Chemical Industry.