Disinfection Of Recirculating Nutrient Solution Of Soilless Cultures By Ultra-violet Radiation

The recycling of nutrient solution has become one of the major factors in soilless cultures. But when the nutrient solution near the infected plants came into the recirculating systems, the pathogens would spread in the whole planting system. What's worse, it would cause the failure of the entire greenhouse. So it was significant that the recirculation water should be disinfected before being reused.In this paper, an ultra-violate disinfection system for recirculating nutrient solution of soilless cultures was developed based on the absorbing of the ultra-violate technology in domestic and abroad. There were four main parts in this system, which were the frame, the recirculation pipeline, the ultra-violate disinfection apparatus and the autocontrol instrument. The frame and the pipeline were designed in a reasonable and compact principle. The system could achieve three different flowing lines according to diverse requirement. A SCM autocontrol instrument was designed to inspect the disinfection system timely, by collecting and analyzing the signal from flowing rate and the ultra-violate intensity sensors. A 30 watts ultra-violate lamp was used in the closed disinfection apparatus.The effect of the ultra-violate disinfection system was tested by using the Fusarium oxysporum f.sp.cucumerinum, which was a kind of root-infecting pathogens in cucumber. The disinfection proportion was 81.3% when the nutrient solution with a transmission value (T10) of 11.58% and a pathogen density of 1.4×10~4 conidia/mL traveled in a rate of 7.9L/min. The disinfection proportion was more than 50%, when the same nutrient solution traveled in the higher rate of 35L/min. The pathogens were totally killed when the water with a transmission value of above 90% and a pathogen density about 1.0×10~5conidia/mL flew at a speed of 36L/min. The disinfection system could meet the demand of the practical applications by growing cucumber in small scale in greenhouse.With the development of soilless cultures and the growing hectare of planting, the ultra-violate disinfection technology would be used more widely.