An ultraviolet LED with peak output at a 265 nanometer wavelength operates in the end cap of a research water treatment reactor at the Air Force Institute of Technology on Wright-Patterson Air Force Base, Ohio. (U.S. Air Force photo/Maj. John Stubbs)
Maj John Stubbs, a bioenvironmental engineer pursuing his doctoral degree in systems engineering at AFIT wrote an article titled “Light emitting diodes may power the future of water treatment” published in the Air Force Civil Engineer Magazine, Vol. 25 No. 2, Summer 2017.
Below is an excerpt from the article. The full article can be read on page 27 here.
Water is a resource we often take for granted, yet we must have it readily available to sustain life and carry out mission-critical operations. Water is used not only for hydration, but also for food preparation, medical treatment, hygiene, construction, decontamination and many additional tasks. There is no doubt that an adequate supply of clean, safe drinking water is critical to the success of U.S. forces carrying out operations worldwide.
In 2013, the U.S. Air Force published an energy strategic plan that identified water as a critical asset and incorporated water into a strategy seeking to balance resource consumption, production and conservation. The plan notes that the Air Force consumes around 27 billion gallons of water per year at an annual cost of $150 million, and energy utilized in water treatment and delivery is closely tied to an overall $9 billion annual energy cost. Furthermore, the plan established a “net zero initiative” for the enterprise whereby an installation consumes no more energy than is generated on the installation, and potable water demand is reduced by capturing and reusing, repurposing or recharging an amount of water that is greater than or equal to the volume of water the installation uses.
In an operational environment that seeks a balance among reduced spending, resource conservation and sustained operations around the globe, the Air Force should consider emerging technologies for water treatment that provide water supply while simultaneously reducing energy costs. One such technological advancement is the use of energy efficient ultraviolet light emitting diodes as a replacement for high energy consuming mercury vapor lamps in advanced oxidation processes utilizing hydrogen peroxide. Although UV LED-based water treatment is now possible, little data has been available on the use of UV LED/hydrogen peroxide for the destruction of soluble organic pollutants that may threaten our water supply.
Current research at the Air Force Institute of Technology has expanded this work to a greater number of soluble organic compounds in order to improve the fundamental understanding of the advanced oxidation processes as they relate to LEDs. UV LEDs are currently being used in bench-top water treatment reactors to test the effect varying parameters, such as optical output power and hydrogen peroxide concentrations, have on resultant degradation and destruction of pollutants. To date, the reactor has been used to degrade six dye compounds (like those commonly seen in food and beverage waste streams) and five chemical compounds (including fuel contaminants, pesticides and explosives constituents).
Much insight has been gained into the underlying kinetics that affect the ultimate destruction of these compounds and the effects that adjusting reactor parameters has on those kinetics. All of the dyes and chemicals tested showed significant degradation, and many saw greater than 90 percent destruction with optimized reactor parameters. Furthermore, by relating the molecular structures of these compounds to their degradability, we may be able to develop a predictive ability for degradation of compounds that have not been tested, based solely on their molecular properties.
The reach of the U.S. military has grown in recent decades, and it is a foregone conclusion that access to clean, safe drinking water will remain a critical requirement for sustained operations. As we seek to balance fiscal constraint with global engagement and adopt a net zero mentality, can LEDs lead the way in reducing water treatment costs in coming years? Time will tell, but the opportunity may be closer than we realize.
Editor’s Note: The author thanks Willie F. Harper Jr., who assisted in the development of this article.