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

Abstract

Plasma activated water (PAW) is an alternative technology to replace commercial fertilizers in agriculture. However, most of the plasma devices generate low concentration of reactive oxygen and nitrogen species (RONS) in a low volume of target liquid which is insufficient for application in agriculture. In this work, a cylindrical dielectric barrier discharge (DBD) reactor is designed to directly or indirectly prepare PAW. The cylindrical DBD reactor consists of nine high voltage electrodes and nine ground electrodes and is operated with compressed air flow. The formation of RONS in PAW is investigated by two methods$\colon$ indirect treatment of water through dissolving plasma generated RONS inside water and direct treatment of water through passing the water inside the DBD reactor. A comparison between the two methods is then made through the measurement of long-lived RONS (mainly hydrogen peroxide and nitrites) and pH inside the PAW. The results obtained after normalization suggest that direct treatment of water could be a better choice for making PAW in large volume. The advantages and disadvantages of using direct and indirect method for making large volume PAW are also discussed.