Microbubble-Enhanced Cold Plasma Activation for Treatment of Flowing Water
Creators: Saedi, Ziya
Publisher: name: University of Alberta Library
Year: 2024

<p>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. This study addresses this challenge through the development of a microbubble-enhanced cold plasma activation (MB-CPA) technology, which uses microbubbles to facilitate efficient interface between plasma discharge and liquid media flow.</p>

<p>In the first part of this investigation, 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. </p>

<p>In the second part, advancements in microbubble-enhanced cold plasma activation (MB-CPA) are presented.  Novel Venturi-type microbubble generators were designed with an expanded range of liquid flow rates, from 3-8 to 3-16 L/min. This design integrates multiple plasma generators to enhance the efficiency of the MB-CPA setup fourfold.These generators also facilitate scaling-up operations for volumes as large as 40L, significantly reducing the timeframe to just 2 hours. Furthermore, an airtight module was devised to facilitate the use of different feed gasessuch as nitrogen and air, alongside precise control of feed gas flow rates. Nitrogen gas utilization enabled the selective production of reactive nitrogen species (RNS), such as nitrite and nitrate. Our findings demonstrate the multifunctionality and efficacy of MB-CPA technology in various water treatment applications from the degradation of chemical compounds and bacterial pathogens to RNS production.</p>

<p>Overall, this thesis represents a significant step forward in advancing PAW technology, offering a green, sustainable, and scalable solution for the diverse industrial and environmental challenges of water treatment. The results and findings of this thesis will help to better understand the working mechanism of MB-CPA and optimize the efficiency of this process. Moreover, this thesis may help the use of MB-CPA for nitrogen fixation and ammonia production processes.</p>