A fully functional, microgravity-compatible microwave sterilization and depyrogenation system (MSDS) prototype was developed that is capable of producing medical-grade water (MGW) without expendable supplies, using NASA potable water that currently is available aboard the International Space Station (ISS) and will be available for Lunar and planetary missions in the future. The microwave-based, continuous MSDS efficiently couples microwaves to a single-phase, pressurized, flowing water stream that is rapidly heated above 150 ºC. Under these conditions, water is rapidly sterilized. Endotoxins, significant biological toxins that originate from the cell walls of gram-negative bacteria and which represent another defining MGW requirement, are also deactivated (i.e., depyrogenated) albeit more slowly, with such deactivation representing a more difficult challenge than sterilization.
Several innovations culminated in the successful MSDS prototype design. The most significant is the antenna-directed microwave heating of a water stream flowing through a microwave sterilization chamber (MSC). Novel antenna designs were developed to increase microwave transmission efficiency. These improvements resulted in greater than 95-percent absorption of incident microwaves. In addition, incorporation of recuperative heat exchangers (RHxs) in the design reduced the microwave power required to heat a water stream flowing at 15 mL/min to 170 ºC to only 50 W. Further improvements in energy efficiency involved the employment of a second antenna to redirect reflected microwaves back into the MSC, eliminating the need for a water load and simplifying MSDS design.
A quick connect (QC) is another innovation that can be sterilized and depyrogenated at temperature, and then cooled using a unique flow design, allowing collection of MGW at atmospheric pressure and 80 ºC. The final innovation was the use of in-line mixers incorporated in the flow path to disrupt laminar flow and increase contact time at a given flow rate.
These technologies can be employed in small-scale systems for efficient production of MGW in the laboratory or in a range of larger systems that meet various industrial requirements. The microwave antennas can also be adapted to selectively sterilize vulnerable connections to ultra-pure water production facilities or biologically vulnerable systems where microorganisms may intrude.
This work was done by James R. Akse, Roger W. Dahl, and Richard R. Wheeler, Jr., of UMPQUA Research Co. for Glenn Research Center. For more information, download the Technical Support Package (free white paper) at www.techbriefs.com/tsp under the Bio-Medical category.
Inquiries concerning rights for the commercial use of this invention should be addressed to
NASA Glenn Research Center
Innovative Partnerships Office
Attn: Steve Fedor
Mail Stop 4–8
21000 Brookpark Road
Cleveland
Ohio 44135.
Refer to LEW-18455-1.
This Brief includes a Technical Support Package (TSP).
Microwave Sterilization and Depyrogenation System
(reference LEW-18455-1) is currently available for download from the TSP library.
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Overview
The document outlines the development and capabilities of the Microwave Sterilization and Depyrogenation System (MSDS), a technology created by NASA's Glenn Research Center to produce medical grade water (MGW) for extended manned space missions. The MSDS is designed to operate efficiently in microgravity environments, such as aboard the International Space Station (ISS) and during future lunar and Mars missions, where access to clean water is critical for medical care and the reconstitution of pharmacological preparations.
Key innovations in the MSDS include an advanced antenna design that enhances microwave coupling efficiency with a high-pressure water stream in the Microwave Sterilization Chamber (MSC). This design allows for effective sterilization and depyrogenation of water, achieving temperatures above 150 °C to eliminate harmful microorganisms and endotoxins. The system operates continuously, requiring only 50 watts of power to heat water at a flow rate of 15 mL/min to 170 °C, thanks to the incorporation of Recuperative Heat Exchangers (RHxs) and a second antenna that redirects reflected microwaves back into the MSC.
The document highlights several unique features of the MSDS, including a Quick Connect (QC) system that allows for sterilization and depyrogenation at high temperatures, followed by cooling to collect MGW at ambient pressure and 80 °C. In-line static mixers are also integrated into the system to enhance contact time and improve sterilization efficiency by disrupting laminar flow.
The MSDS has undergone rigorous testing, demonstrating its effectiveness in sterilizing and depyrogenating water contaminated with high levels of bacteria and endotoxins. In one test, deionized water with significant microbial contamination was processed over extended periods, successfully meeting MGW requirements.
The potential applications of the MSDS extend beyond space missions. In the private sector, the technology can be adapted for small-scale systems in laboratories and larger industrial applications, including portable units for remote locations and humanitarian emergencies. The MSDS can also be utilized by military services to ensure access to clean water in challenging environments.
Overall, the MSDS represents a significant advancement in sterilization technology, with promising implications for both space exploration and terrestrial applications.
