Stable and efficient microbubble-enhanced cold plasma activation for treatment of flowing water

Cold plasma technology has received immense attention in several fields including wastewater treatment, disinfection, food processing and storage, and agriculture due to its ability to produce reactive species at low energy input. However, the scalability of generation of plasma activated water (PAW) still remains a challenge. A microbubble-enhanced cold plasma activation (MB-CPA) technology leverages small bubbles for effectively interfacing plasma discharge in a gas phase and a flow of liquid media. In this study, we develop a stable and efficient approach for the continuous production of PAW by maximizing the transfer of active species generated during plasma discharge to water flow. Novel Venturi-type microbubble generators were designed for the production of PAW by maximizing the rapid transfer of active species generated during plasma discharge in air. Key geometrical features of the tubes including the position and the opening size of the air inlet were tuned, aiming to transfer active species in a wide range of liquid flow conditions. The performance of our flow systems was evaluated by using pure water, buffered saline, and real river water containing micro-pollutants. We found that MB-CPA can effectively eliminate chemical compounds such as dye and antibiotic residues, as well as biological pathogens like Gram-positive and Gram-negative bacteria. In a cell viability assay, the technology exhibited cytotoxic effects against cancerous cells, specifically HeLa and MCF-07 cell lines. This multi-functionality underscores the versatility of MB-CPA, positioning it as a multifaceted solution for both water and wastewater treatment. Our work shows that the designed MB-CPA system represents a promising and sustainable technological advancement, offering a green alternative for the widespread activation of water in various applications.