Assessment of UV-C Radiation for Bacterial Inactivation of Hydroponic Nutrient Solutions in Dynamic System

Hydroponics, a soilless cultivation method, is increasingly being adopted for its ability to produce high-quality vegetables while reducing resource usage and minimizing the risks of soil-borne pathogens. However, the reuse of nutrient solutions in hydroponics can accelerate the spread of pathogenic microorganisms. This study aimed to evaluate the bacterial decontamination effects of UV-C light (254 nm) on a hydroponic nutrient solution. The solution was contaminated with Escherichia coli and irradiated with UV-C at energy doses of 20.37 and 489.02 mJ/cm². Experiments were conducted under both static and dynamic fluid conditions to assess bacterial inactivation and changes in electrical conductivity over time. Results showed no significant change in electrical conductivity after 144 hours of UV-C exposure. Under static conditions, bacterial inactivation was observed, with a reduction of 1.7 log CFU/mL at 20.37 mJ/cm², though no significant additional reduction was seen at the higher dose. However, dynamic conditions resulted in greater inactivation, with reductions of 4.2 and 5.2 log CFU/mL at 20.37 and 489.02 mJ/cm², respectively. These findings suggest that fluid agitation plays a crucial role in enhancing UV-C efficiency by preventing bacterial sedimentation, which occurs in static conditions. The use of UV-C as an eco-friendly disinfection method appears promising for hydroponic systems, as it does not alter the composition of the nutrient solution.