Comparison of Direct and Indirect Dielectric Barrier Discharge Treatment Routes for Large-scale Plasma-Activated Water Production

Abstract

This study presents a comparative analysis of direct and indirect dielectric barrier discharge (DBD) approaches for the upscaled production of plasma-activated water (PAW). A cylindrical DBD reactor, consisting of nine high-voltage and nine ground electrodes operated with compressed air, was designed to investigate the generation of plasma and production of reactive oxygen and nitrogen species (RONS). The production of reactive species was evaluated through two distinct methods: indirect treatment, involving the dissolution of plasma-generated gas into water, and direct treatment, where the water flows through the active discharge region. Performance was assessed through the measurement of long-lived RONS (primarily hydrogen peroxide and nitrites), with results further analyzed through the determination of energy yields ($g/kWh$) and pH. The results indicate that the direct treatment approach achieves significantly higher chemical production efficiency, identifying it as the more effective strategy for the upscaled production of PAW. The relative advantages and disadvantages of both direct and indirect approaches are discussed in the context of system optimization and industrial scalability.