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Completed TRL 3 (started at 2, targeting 3)
Project Objective
The Plasma-Activated Water project (PAW) will determine if plasma-activated water works as a viable anti-biofilm technology for the wastewater tank on the International Space Station (ISS) and in future spacecraft wastewater systems.
Project Description
The Environmental Control and Life Support System (ECLSS) for Lunar and Martian crewed missions needs to be able to undergo and restart from prolonged dormant periods during uncrewed operations. On board ISS, biofouling has been seen in urine-to-water processing systems at levels that inhibit operation and necessitate replacement of components. ECLS systems need a robust manner of preventing operation-prohibitive biofouling for habitats that will not have continuous human operation like the ISS. Understanding, preventing, and mitigating the effects of dormancy on ECLS systems are ongoing efforts at MSFC and across NASA. A recent Kennedy Space Center study described the properties and potential space applications of plasma activated water (PAW) – where a plasma generator is activated in water to generate chemical species that increase the water’s acidity. Using ambient air as the feed gas, this study showed that nitrates in the PAW aided in plant growth, adversely affected microbial growth, and maintained pH for up to a year. The sanitizing properties of PAW have also been shown in scientific literature relating to food safety science and medical applications. We are asking for $50k to conduct an initial characterization of the biofilm growth prevention capacity of PAW for sections of a potable water processor where microbial growth is most prevalent. The test setup will attach into the existing Biofilm Test Stand at MSFC to take the concept to >=3, proving that the technology can be applied for water processing purposes and the testing can be compared to previous biofilm test data.
Project Results and Conclusions
The PAW project successfully implemented a plasma torch into the MSFC Biofilm test stand for evaluation of biofilm prevention potential in space craft wastewater systems. The PAW setup utilizing the plasma torch provided plasma activated water produced from ersatz (a simulant of the wastewater in the system) to the bioreactors over the course of the nine-week test. Sampling was completed every three weeks for microbial evaluation, with chemical sampling data taken every week.
The results were fairly conclusive. Although the PAW affected the cellular membrane, evident by the (4′,6-diamidino-2-phenylindole) DAPI imaging taken every three weeks with the microbial samples, the plasma activated water in this configuration was not effective in preventing biofilm. Microbial data in the form of drop plating to determine CFU/cm^2 and log reduction of biofilm growth concluded the plasma-activated water made the biofilm growth equivalent to or worse than the control. Chemical sampling data every week confirmed that the PAW system was working as intended, so PAW system failure was not the reason for the biofilm growth.
Although the PAW system in the initial testing failed to prevent biofilm, there are avenues for further exploration into the technology. Theoretical dosage was calculated for the first nine-week test, but a more extensive dosing regime (using the plasma torch to generate activated water more frequently) could overcome the biofilm's resistance to PAW. DAPI images previously mentioned also exhibited a cellular membrane effect allowing for greater diffusion across the cell wall. This effect could be paired with a biocide to increase the biocidal effectiveness.
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