Bio-aerosol and Particulate Matter Evaluation in the Presence of a Lab-Scale Anaerobic Digester for Volatile Fatty Acids' (VFAs) Production

The increasing number of employees dedicated to Green jobs may be subjected to novel risks for their health. Operators involved in the anaerobic digestion deal with the manipulation of organic waste of different nature that may include pathogen microorganisms. This paper deals with the evaluation of biological contamination due to the presence of bio-aerosol and particulate matter in the air of a laboratory environment (?50 m3) which hosts a 3-L anaerobic digester for the production of volatile fatty acids (VFAs). The study was performed while the bio-reactor was being loaded, the digestate was removed, and food waste was handled. To assess the concentration of microorganisms in the air, an active air sampler was used, which exposed a certain amount of air to a growth medium. The evaluation of total bacterial count (using plate count agar at 22 and 37 °C) and yeast/fungi (using Sabouraud dextrose agar at 22 °C) was carried out. Particular matter was performed monitoring the amount in air of six PM10 fraction levels (0.3-0.5 µm, 0.5-0.7 µm, 0.7-1 µm, 1-2 µm, 2-3 µm, 3-5 µm) during time: data analysis was conducted using the principal component analysis (PCA) statistical method. Although the results showed how the concentration (CFU/m3) of biological agents in the air significantly raised during the working activities, a low degree of contamination was detected. Moreover, the level of PM10 was far below the threshold admitted by the Italian law (D.Lgs n. 155/10). As expected, it was also demonstrated that the removal of digestate was the activity that mainly affected the presence of particular matter in air.