Selective Production of Plasma-Activated Water by pin-to-plane DBD Plasma for Microgreen Cultivation and Microbial Safety in Agriculture

Abstract

This study examined a multi-pin-to-plane dielectric barrier discharge (DBD) plasma generator, powered by a 6 kV<inf>rms</inf>, 60 W neon-sign transformer, to enhance tap water for agricultural use. Plasma parameters were optimized to maximize the levels of beneficial compounds in plasma-activated water (PAW). Higher input voltage and longer treatment time increased hydrogen peroxide (H₂O₂), while nitrate (NO₃⁻) and nitrite (NO₂⁻) increased under air atmospheres but were not detected under argon (Ar). PAW composition was influenced by electrode configuration and gas type. To selectively enhance NO₃⁻ and NO₂⁻ while minimizing H₂O₂, air should be used as the working gas with moderate electrical settings and a short treatment time. Conversely, H₂O₂-rich with low-nitrogen oxides (NOₓ) PAW is favored by operating in Ar at increased voltage and extended treatment time. Consistent with these tunable chemical profiles, PAW generated under the optimized conditions significantly enhanced the germination and early growth of curly-kale seeds, while a 20-min treatment of 400 mL tap water achieved up to ≈6.8-log₁₀ inactivation of Escherichia coli. Together, these results indicate that plasma activation can be selectively configured to improve water quality, promote plant growth, and ensure microbial safety in agriculture.