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Abstract
The release of aerosols from aerated liquids is of environmental concern when the liquid contains potentially hazardous contaminants. The aerosol generated by the aeration of a fermentation broth was measured in a vessel of 0.1 m3 total capacity. The influence of air flow rate, agitation rate, and diffuser diameter on the size distribution and particle number concentration was investigated. Aerosols in the size range of 0.8–15 μm were measured by an Aerodynamic Particle Sizer. Measured particles were in the respirable size range and were large enough to carry bacteria. It was found that the composition of the particles was close to that of solid residues after water evaporation. The particle concentration in the air stream depended directly on the broth concentration. Particle volume release rates on the order of 16 mm3/m2˙min were observed for superficial air velocities of about 0.2 cm/s and liquid agitation rates of 75 and 130 rpm. The mean size of the particles increased with increasing agitation and air flow rates. The generation of large particles (above 2 μm) is higher for smaller bubbles. The measurements indicate that a large number of particles below 0.8 μm size are generated from aerated broths. Respirators are recommended when aeration of liquid containing hazardous components is performed in open vessels.