Non-thermal plasma inactivation of viruses in water solutions

Low-temperature (cold) gaseous plasma is a promising alternative for water treatment owing to its mild operating conditions, low environmental impact, and demonstrated effectiveness at degrading all types of organic molecules. It is being extensively researched as a novel tool for water treatment purposes, although it is still restricted to laboratory scale since disinfection mechanisms and operational parameters are numerous and inadequately understood. Different plasma treatment setups and approaches for disinfecting liquids are reviewed and critically evaluated. The original literature data is normalized and a meta-analysis is performed, providing insight into the major parameters affecting virus inactivation. The reported results differ significantly, but the virus inactivation efficiency (presented as D-value) is of the order of 10 s in all reports. The D-value does not depend much on the initial viral load although the authors probed a broad range from about 104 to 1011 PFU/mL. Different authors used plasma sustained at various powers. We found no correlation between the D-value and plasma power in the range of reported values, i.e., between 6 and 400 W/mL. The D-value increases with increasing energy consumption in the range between about 10 and a few 1000 kWh/m3. Inactivation curves of various treatment setups demonstrate the efficiency and disinfection kinetics with which cold plasma is able to destroy viruses in solutions. Although being a promising method for future applications, there is still an obvious lack of data to optimize the treatment parameters for large-scale applications.