On Sept. 27, 2016, Elon Musk, CEO of SpaceX, addressed the International Astronautical Congress. Musk spoke on his ambition for mankind to visit, and eventually colonize, Mars. “I think the most important thing [for the preservation of humanity] is to create a self-sustaining city on Mars,” Musk said. Meaning, humanity will need to develop technology to recycle or reuse almost all of our resources to not only survive, but also to thrive outside Earth’s environment.
The first step in this ambitious goal is to perfect the reuse of resources on the International Space Station (ISS). Developing the most sophisticated, cutting-edge technology is vital, as the crew relies on these systems to provide life-critical resources. Currently, 88% of the water on the ISS can be reused, while 12% is lost to waste—roughly 100 mL per person per day. Advancements in light emitting diodes (LEDs) within the ultraviolet (UV) spectrum can help mitigate the possibility of biocontamination in the water system and improve the reuse rate.
Current Issues
The relatively large distance between the ISS and the closest support back on Earth is an issue we can no longer ignore if we are to extend our extraterrestrial ambitions. Monthly resupply missions are needed to bring vital resources that cannot be recycled on-orbit. This delivery service uses a 3 million-hp rocket to catch up and dock with the ISS as it speeds around the Earth at 17,000 mph. This is an expensive task, costing approximately $2,000 per pound of cargo. Unfortunately, the problem becomes even worse looking towards Mars, which needs much bigger rockets and has a travel time of six to nine months, compared to just a few hours to reach the ISS. Any reduction in consumables and resupply needs will help in the journey to colonize the red planet.
Current ISS systems for air and water do not include real-time biocontamination monitoring. In order to test microorganism levels in drinking water, a sample must be sent back to Earth for laboratory testing. This process takes three to six months from sample collection to see results. This delay could be crucial because the crew aboard the ISS has limited sources of drinking water and could be unknowingly drinking contaminated water for months before an alarm is raised. If a contamination event were to occur, the first indications likely would be crew sickness rather than any laboratory result, the consequences of which could be fatal in such a dangerous and isolated environment.
UV-C LED systems (left) have been integrated into the operation of commercial devices, such as a steam over (right).
LED Introduction
Looking to the future of manned space exploration, the current drinking water delivery system aboard the ISS was evaluated and found in need of improvement. Biocontamination Integrated Control for Wet Systems for Space Exploration (BIOWYSE), a European Commission Horizon 2020-funded project, was launched to test a new type of system that uses real-time microbial monitoring—ATPmetry—and deep ultraviolet light emitting diodes (UV-C LEDs) for disinfection. The intent of the project is to develop an integrated, autonomous, chemical-free system to control and monitor biomass growth in potable water systems aboard the ISS.
Two years into the project, the consortium has developed the main components of the system, which include a number of technologies, including AquiSense Technologies’ patent-protected UV-C LED Water Decontamination Module. Integration testing began in March 2018, and will be followed by laboratory and field testing through to the end of the year.
BIOWYSE functions autonomously, with real-time microbial monitoring. If pathogen levels are too high in the main system, the UV-C LED disinfection module is activated, and the water is decontaminated in recirculation and direct delivery modes. Currently, the BIOWYSE project is designed as a backup system to ensure that the drinking water supply remains safe to drink; though not yet implemented, the technology stands as a precursor to main water handling systems of the future. BIOWYSE is one of the first major international projects to employ UV-C LEDs.
Traditional mercury UV lamps were ruled out of the project, as mercury is one of many banned substances on-board the ISS and the risk of lamp breakage and a mercury spill is too high. Comparatively, UV-C LEDs are made from common elements with low toxicity, bound into a stable crystal form; environmental factors surrounding breakage and disposal are therefore not a concern. UV-C LEDs offer the same type of disinfection as traditional UV lamps, but with a small, robust light source.
UV-C LEDs solve many of the issues that continue to cause problems for chemical treatment and mercury-based UV disinfection, including exposure to hazardous materials. Adding too much of these chemicals can produce disinfection byproducts known to be detrimental to human health under prolonged exposure. Besides the preventive health benefits offered by UV-C LEDs, there are several additive benefits that are key for space applications. The solid-state technology of the LED light source and its durability, compact footprint, and minimal maintenance requirements make UV-C LED systems ideal for this new market. Looking forward, these systems offer new applications for water disinfection in markets back on Earth.
The UV-C LED disinfection system elements are made from low-toxicity elements bound into a stable crystal form, eliminated the threat of breakage.
Terrestrial Relevance
Current markets for UV-C LED-based systems such as commercial appliances and healthcare disinfection applications have benefited from research and development associated with the BIOWYSE project. For example, the environmental durability and quality hurdles met for space habitats have provided commercial appliance manufacturers and medical device makes with increased confidence regarding this new technology. The ability to power UV-C LED systems from low-voltage supplies such as solar panels or batteries is ideal for off-grid applications. In addition, the durability of these systems has seen their integration into portable water disinfection applications such as military and disaster relief systems, where shock resistance is highly valued. Since the additive benefits discussed are intrinsic to the UV-C LED sources, and not derived from intensive design, these self-same devices can easily be transferred from space station to refugee camp to office water cooler.
Demonstration of the features UV-C LEDs offer can be seen in products such as the PearlAqua Micro series, which features an IP67-rated, shock-resistant housing and DC power requirement as low as 4.2 W. Telemetry and digital control also are standard across the product range. It has been integrated into commercial products in the food and beverage market. One example is a commercial steam oven produced by Distform FoodService Technology, where the warm moist environment has the potential to propagate the growth of harmful pathogens such as listeria, salmonella, clostridium and E. coli. To mitigate this risk, the integration of disinfection module to the incoming water supply is shown to be effective. Other applications are being scaled-up or are already in mass production, including point-of-use disinfection in water coolers.
The risk of biocontamination in an enclosed self-sustaining environment, whether in orbit around Earth or on the surface of Mars, has life-or-death consequences. Advanced UV-C LED disinfection technology can be used to make these recycling systems much more reliable and practical, opening new possibilities for waste treatment and environmental control. Disinfection technologies designed for advanced applications, such as space exploration, can be directly transferred to solve more practical everyday biocontamination issues in air, water and surfaces. UV-C LED systems offer greater flexibility and a new set of incremental benefits that will open up new markets for UV technologies. Simply put, UV-C LED devices are developing rapidly in space and here on Earth, casting off the limitations of previous technologies.
