Development and test of nutrient solution disinfection machine by combining UV with ozone

In order to make full use of superiority of ultraviolet radiation (UV) and ozone (O3), to disinfect nutrient solution in a closed soilless cultivation system, a kind of ultraviolet-ozone combined-type nutrient disinfection machine was designed, tested and inspected. Prototype mainly included a UV sterilizer, four Venturi jet devices, an ozone generator, a self-suction pump, a ABS piping and automatic control equipment, etc. In operation, the collected nutrient solution after irrigation was pumped firstly through the connected parallel Venturi throat and mixed with ozone which produced by ozone generator to inhibit microbial pathogens by oxidation. Then it passed through the ultraviolet disinfector where UV light radiation killed the pathogens further. The disinfection rate could be increased compared with UV or O3 alone. A commercial prototype was manufactured and its performance was tested by disinfecting nutrient solution from tomato hydroponics, which was used for over 180 days continuously. The main pathogens such as bacteria and fungi in the nutrient solution were sterilized by UV, O3 and UV+O3 separately, and disinfection rates were detected. The total disinfection rates of three methods were 70.6%, 15.9% and 89.9%, respectively. It was inferred that the method of ultraviolet-ozone combined-type nutrient disinfection can reach better sterilization effects than single ones, and can improve disinfection efficiency greatly with a synergy effect.