Removal of ethylene and bioaerosol by chlorine dioxide using a chemical scrubbing system in a fruit and vegetable storage facility

Ethylene (C2H4) and bioaerosol are commonly present in the inside atmosphere of postharvest fruit and vegetable storage facilities, which may affect the aging of postharvest fruit and human health. We have assessed the feasibility of chlorine dioxide (ClO2) as the scrubbing solution in a chemical scrubbing tower for simultaneously removing C2H4 and bioaerosol emissions from a gas stream. Parameters such as the ClO2 concentration, contact time, and liquid-to-gas (L/G) ratio were examined with the aim of determining the optimal operating conditions. Using the system reported here, the optimal C2H4 removal efficiency was 99.5% when 500 ppm ClO2 was used at a reaction time of 30-60 s under a continuous non-recycle ClO2 flow mode. In terms of C2H4 removal, a greater L/G resulted in a higher C2H4 removal efficiency up to the optimal ratio of 12.5. In terms of the simultaneous removal of C2H4 and bioaerosol, the removal efficiency of C2H4 was 99.2% and those for the bioaersols of Escherichia coli and Staphylococcus aureus were 99.92 and 99.10%, respectively, under a continuous non-recycle flow mode. Our results also indicate that oxidation reduction potential (ORP) can be a valuable indicator for the timing of the replacement of the scrubbing solution in the system under a continuous recycle flow mode. Additional confirmation of the feasibility of the ORP as an indicator of C2H4 and bioaerosol removal in situ was obtained in a 3-month test of our system in continuous recycle flow mode with the periodical replacement of scrubbing solution, ClO2. The removal efficiencies for C2H4, bacterial and fungus aerosol, and total hydrocarbon compounds (THC) were 83.4, 96.8, 96.1, and 76.5%, respectively. Our results prove that ClO2 is an excellent scrubbing solution in the chemical scrubbing tower for the removal of C2H4 emissions and bioaerosol. We demonstrate, for the first time, the feasibility of this system in a fruit and vegetable storage facility.