Effects of the Circulation Pump Type and Ultraviolet Sterilization on Nutrient Solutions and Plant Growth in Plant Factories

Abstract

<jats:p>Hydroponic systems in plant factories can be categorized into recirculating or noncirculating systems. In this study, the effects of various commercially available circulation pumps, including a centrifugal magnetic drive pump, a regenerative self-priming pump, and a submersible pump, were experimentally explored. In addition, the effects of an ultraviolet sterilization system on the ion concentrations in nutrient solutions were examined. The concentrations of sodium, potassium, magnesium, calcium, nitrate, sulfate, and ferric (Fe<jats:sup>3+</jats:sup>) ions in the nutrient solution were measured. For all three types of pumps, the results indicated that there was no significant effect on the concentrations of ions in the nutrient solution. However, the concentration of Fe<jats:sup>3+</jats:sup> ions decreased significantly after the nutrient solution was treated by a ultraviolet sterilization system for 48 hours. In addition, the effects of the three types of pumps on the growth of butterhead lettuce (<jats:italic>Lactuca sativa</jats:italic>) were examined. The temperature records during the pump circulation tests showed that the nutrient solution temperature of the regenerative self-priming pump increased by 15.5 °C (from 20.5 to 36 °C), which caused yellow seedling, scorching on the leaves, and browning of the roots. The ion concentration in the nutrient solutions and total fresh weight of butterhead lettuce did not show any noticeable difference between the centrifugal magnetic drive pump and the submersible pump. In this paper, we clarify the cause of the decreasing iron concentration and provide a guideline for selecting the pump for circulating hydroponic systems in plant factories.</jats:p>

Plants Dictate Root Microbial Composition in Hydroponics and Aquaponics

“…Demonstrating that the rhizosphere community composition is associated with the plant more strongly than the presence of exogenous colonizing bacteria implies that focusing efforts on supporting plant health rather than on water sterilization will better protect crops. Sterilization of incoming water and media is widely used in hydroponics to discourage the proliferation of pathogens ( Ehret et al, 2001 ; Shimizu et al, 2007 ; Raudales et al, 2014 ; Liu and Huang, 2019 ; Zheng et al, 2019 ) albeit at the cost of reducing overall microbial diversity – both beneficial and harmful microorganisms – potentially opening niches for rapid colonization by r-strategists ( Vadstein et al, 2018 ).…”

Sterilization of Harmful Microorganisms in Hydroponic Cultivation Using an Ultraviolet LED Light Source

“…Moreover, a module was produced comprising a quartz pipe with an inner diameter of 10 mm installed on top of 14 LED bars, which can be applied to circulating plant factories. (15) Figure 2 shows the UV-C module for which a circulating transparent tube was applied. A regulator was attached to control the amount of light to test the sterilization effect according to the change in light output.…”

Design of UVA Ultraviolet Disinfection System for Nutrient Solution Residual Liquid and Development of Microbial Online Monitoring System

“…A model was designed to describe the relationship between the nutrient solution volume, the logarithmic survival rate and the UVA flux relation [7]. For removing toxic substances, such as organic acids and nutrient solution microorganisms emitted by plants, some nutrient solution waste liquid sterilization methods, such as ozone, heating, sand filtration, advanced oxidation disinfection, activated carbon, nano-TiO 2 catalysis and comprehensive sterilization, can be used [8][9][10][11][12]. For the recycling of the nutrient solution residual liquid, these disinfection methods may obviously affect the composition ratio of the nutrient solution.…”