Characterization of of bioaerosol emissions from two biofilters during treatment of toluene vapours using epifluorescence microscopy

Emission of bioaerosols from biofilters during the treatment of toluene vapours was studied. A non culture-dependent technique, known as epifluorescence microscopy (EM), with several fluorochromes was used to characterize and quantify bioaerosols. The bioaerosol emitted concentrations were between 6.4 x 10(5) and 13 x 10(8) cells m(air)(-3) compared with the bioaerosol concentration in ambient air, which was 3.0 x 10(7) +/- 7 x 10(6) cells m(air)(-3). EM allowed for a better estimation of bioaerosol concentrations than culture-dependent techniques. Bioaerosol emission was dependent on the packing material. Perlite was a better packing material in terms of removal efficiency (RE; RE of 60%), with a lower bioaerosol emission (7 x 10(7) cells m(-3) (air)) than Tezontle (RE = 40%; 1.3 x 10(8) cells m(-3) (air)). The main drawback of perlite was acidification of the bed. Bioaerosols in biofilters A and B were composed of Gram-negative bacteria (45% and 40%, respectively), a similar percentage of Gram-positive bacteria (28%) and fungi (27% and 32%, respectively). After the shutdown periods, Gram-positive bacteria were predominant (similar to 60%). The biomass concentrations in leachates were twice those in the air flow and were mainly composed of fungi. Overall, the EM technique is a valuable tool to characterize and quantify bioaerosols in biofilters without under evaluation. This is the first estimation of bioaerosol emissions by biofilters inoculated with a microbial consortium using a noncultivable technique. (C) 2017 Elsevier Ltd. All rights reserved.