Inactivation of Pseudomonas aeruginosa and Methicillin-resistant Staphylococcus aureus in an open water system with ozone generated by a compact, atmospheric DBD plasma reactor

Bhaswati Choudhury,Subrata Roy,Navya Mastanaiah,Judith A Johnson,Sherlie Portugal

doi:10.1038/s41598-018-36003-0

Bhaswati Choudhury, Subrata Roy + Show 3 more

Open Access

https://doi.org/10.1038/s41598-018-36003-0

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Abstract

Ozone is a well-known disinfecting agent that is used as an alternative for chlorine in many applications, including water decontamination. However, the utility of ozone in water decontamination is limited by high electrical power consumption and expensive, bulky equipment associated with ozone generation. This study investigates the effectiveness of a lightweight, compact surface dielectric barrier discharge (SDBD) reactor as an ozone generator to inactivate Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA) in an open water system. Experimental details are provided for ozone generation technique, mixing method, ozone concentrations in air and water, and input energy required to produce adequate ozone concentrations for bacterial inactivation in a contaminated, open water system. Specifically, an active plasma module (APM) reactor system of size 48 cubic centimeters, weighing 55 grams, with a maximum ozone yield of 68.6 g/KWh was used in atmospheric conditions as the source of ozone along with an air pump and a diffusion stone for mixing the ozone in water. Over 4-log reduction in P. aeruginosa concentration was achieved in 4 minutes with 0.1 mg/L ozone concentration in an open water system using 8.8 ± 1.48 J input energy. Also, over 5-log reduction in MRSA concentration was achieved in 2 minutes with 0.04 mg/L ozone concentration in an open water system using 4.4 ± 0.74 J input energy.

Highlights

Ozone is an attractive alternative for free chlorine and chloramine disinfection; with a higher thermodynamic oxidation potential, less sensitivity to organic material, and better tolerance for pH variations while retaining the ability to kill bacteria, fungi, viruses, as well as spores and cysts[11,12]
Dissolved ozone concentration in water, exposure time, and input energy required to produce adequate ozone concentrations were identified as significant factors contributing to optimal and effectual inactivation
Direct measurement of dissolved ozone in water was found to be critical for understanding the ozonation experiments and determining the minimal ozone concentration and input energy required for bacterial inactivation

Summary

Introduction

Ozone is an attractive alternative for free chlorine and chloramine disinfection; with a higher thermodynamic oxidation potential, less sensitivity to organic material, and better tolerance for pH variations while retaining the ability to kill bacteria, fungi, viruses, as well as spores and cysts[11,12]. Plasma reactors employing corona discharge or dielectric barrier discharge (DBD) are the most common ozone generation devices currently available[21,22] They are limited by high electrical power consumption, low ozone production and expensive-bulky equipment[21,22]. DBD plasma is produced when a potential difference is applied across two electrodes on opposite sides of a dielectric (insulator) material This leads to the formation of filamentary micro discharges and ionization of the surrounding gas[22]. This study establishes the effectiveness of a compact, lightweight DBD plasma reactor in generating ozone and decontaminating water in an open system with air as the oxygen source. This is an attempt to fill the knowledge gap associated with details on ozone generation techniques, ozone mixing processes, ozone concentration in water and power requirements for achieving bacterial inactivation in existing literature on inactivation kinetics of bacteria in water[28,29,30,31]

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