Influence factors and health risk assessment of bioaerosols emitted from an industrial-scale thermophilic biofilter for off gas treatment

Abstract

Bioaerosols emissions from an industrial-scale thermophilic biofilter (TBF) for sludge drying exhaust treatment were investigated by varying the inlet gas flow rate and water containing rate (WCR) of the packing materials (polyurethane foam cubes, PUFCs). Both bacteria and water-soluble ions (WSIs) were detected in bioaerosols. When the WCR of PUFCs was 37%, with the increase of flow rate from 1500 to 3500m3/h, concentrations of bacteria in bioaerosols increased from 449±27 to 643±46 CFU/m3. Variation in flow rates had similar effects on WSIs. At a constant flow rate of 3500m3/h, bacterial emissions increased from 1112±314 to 1778±157 CFU/m3 when the WCR of PUFCs increased from 44% to 65%. Similarly, the total concentrations of WSIs emissions also increased from 19.21 to 30.57μg/m3 with the rising of WCR. The bacterial populations in bioaerosols were determined via polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) technology. Source apportionment results showed that more than 80% of the bacteria in bioaerosols originated from PUFCs. At the TBF outlet, health risks were associated with gaseous compounds (e.g. SO2, H2S, and 1,2-dichlorobenzene) rather than bioaerosols. Appropriate management and control measures are required to reduce the risks of these compounds.