Comparative analysis of regenerative in situ electrochemical hypochlorination and conventional water disinfection technologies for growing ornamental crops with recirculating hydroponics

Abstract

Capturing and reusing fertigation drainage is a key strategy for maximizing greenhouse production efficiency while minimizing the impact of wastewater discharge on receiving ecosystems. Fertigation drainage, in this regard, refers to irrigation water mixed with fertilizer that has once passed through soilless culture. Although an economically and environmentally prudent practice, recirculating fertigation solutions does pose an increased risk of pathogen proliferation. There are many water disinfection technologies currently available to growers, including ozone (O3(aq)) and Advanced Oxidation Processes (AOP). Beyond currently available treatment options there are emerging technologies that have yet to be optimized for recirculating hydroponics. Electrochemical systems based on Dimensionally Stable Anodes (DSA) offer a novel method for disinfecting fertigation. Using Cyclamen persicum as a representative greenhouse floriculture crop, fertigation solutions were inoculated with Fusarium oxysporum isolated from a diseased C. persicum sample. Following inoculation, solutions were treated with one of either a DSA electrochemical system, a UV/Ozone AOP system, or ozonation. Solutions were then applied to the crop and disease progression was monitored. The positive control group (F. oxysporum added) exhibited pathogenicity following the recirculation of the fertigation solution, while the negative control (F. oxysporum absent) did not show pathogenicity in C. persicum. All water treatment systems achieved a log-4 reduction in F. oxysporum, which prevented pathogenicity in plants. Furthermore, there were no significant differences in plant physiology between the water treatment methods in comparison to the negative control group. However, all treatments performed significantly better than the positive control group which experienced pathogenicity. Solution nutrient analysis indicated stability across all treatments. Energy consumption was also monitored and demonstrated a two-fold reduction in electricity use with the electrochemical flow cell (EFC) compared to the AOP system.