Performance and dose validation of a coiled tube UV-C reactor for inactivation of microorganisms in absorbing liquids

• Published in: Journal of food engineering Vol. 138; pp. 45 - 52
• Main Authors: Müller, Alexandra, Stahl, Mario R., Greiner, Ralf, Posten, Clemens
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.10.2014
• Subjects: Absorptivity; Biodosimetry; Coiled tube reactor; Escherichia coli; Fluid dynamics; Fluid flow; Hydraulics; Inactivation; Iodide/iodate actinometry; Liquids; Reactors; Residence time distribution; Tubes; UV-C; UV-C; Residence time distribution; Biodosimetry; Iodide/iodate actinometry; Inactivation; Coiled tube reactor
• ISSN: 0260-8774; 1873-5770
• DOI: 10.1016/j.jfoodeng.2014.04.013

•The hydraulic conditions of a coiled tube reactor were characterized.•The effect of flow condition and absorption coefficient on UV-C energy delivery was investigated.•Actinometric dose specification describes inactivation kinetics in absorbing liquids.•Helpful methods for the comparison of different reactor designs are shown. The inactivation performance of a coiled tube reactor was investigated in respect to hydraulic parameters and the impact of flow conditions and absorption on the UV-C energy delivery. Data of the residence time distributions using tracer step response indicate full use of the reactor volume and flow behavior close to ideal plug flow with increasing Reynolds number. Based on the hydraulic characteristics of the coiled tube, the used reactor appears to have an effective design for inactivation. Even though the hydraulic characteristics were similar to plug flow conditions, the attenuation of the UV-C energy delivery due to the presence of absorptive compounds in the liquid remains an influencing parameter on the inactivation performance. In addition, the UV-C dose was evaluated by calculation of the theoretical maximum UV-C energy input and actinometric measurements using iodide/iodate actinometry. Both dose specifications were evaluated for their suitability to describe inactivation kinetics of Escherichia coli ATCC 8739 in clear and absorptive liquid. Since the flow influences the inactivation performance in absorptive liquids, actinometric dose is suitable to describe inactivation kinetics in absorptive liquids.