The Homeland Defense and Security Information Analysis Center received a request for research and analysis of alternative methods for water purification to support deployed troops. HDIAC provided a comparative data analysis, as well as cost-benefit analyses of water purification systems using innovative technologies in materials science, nanoparticles, graphene and hybrid techniques.
Managing clean water systems is challenging for forward operating bases in remote and underdeveloped locations. Some FOBs lack access to potable water and raw water sources may contain chemical or biological agents that require treatment before use.  Water supplies in the Middle East are especially important, as troops in desert areas must drink more water in an area where the resource is scarcer.  Therefore, the U.S. Department of Defense spends more than $500,000 per day transporting and supplying 20,000 troops with bottled water. 
Enemy combatants also target supply convoys, making the logistics of importing bottled water dangerous to the warfighter.  During the 2007 fiscal year, the total casualties occurring during water resupply convoys numbered 15 in Afghanistan and 53 in Iraq.  Technologies in water filtration can meet the needs of FOBs while reducing operational costs, improving sustainability and reducing the need for water convoys. 
In order to adopt alternative water filtration technologies, the DoD’s unique requirements must be considered. One requirement is a wholly mobile system, which is necessary for troops on the move. Current military iterations of water filtration systems, such as the Lightweight Water Purification System and Tactical Water Purification System are semi-mobile, but require a truck or Humvee for transportation.  Larger systems, such as the Reverse Osmosis Water Purification Unit, rely on diesel generators;  thereby increasing demands on additional energy resources and increasing the weight of the systems, which decreases mobility. Larger filtration systems can remove a wider variety of contaminants than their smaller counterparts,  which may lack the ability to remove dissolved salts, such as lead or mercury; however, these systems are immobile.  For the DoD, an ideal system could remove a variety of contaminants while remaining compact enough for small forces to transport. Costly operations to bring water to the troops prompts military research labs to develop alternative systems capable of filtering and desalinating water sources in the Middle East, Pacific Islands and anywhere troops are deployed. 
Each water filtration system’s effectiveness is largely dependent on its filters. Many water purification systems fielded by the U.S. military use reverse osmosis in combination with carbon, ceramic, sand or diatomaceous earth filters. [8,9] Reverse osmosis can remove dissolved materials as small as .001 microns by filtering the water through a semipermeable membrane.  Additional filtration methods vary by system, but can include carbon and ion exchange filters to remove chemical and nuclear agents  and ultraviolet light to kill microorganisms. [10,7] Although these systems prove effective at removing contaminants, only one system, the Small Unit Water Purification System, possesses high levels of filtration while remaining mobile. The SUWPS produces up to 750 gallons of decontaminated and desalinated water daily and weighs only 80 pounds.  Despite its advanced capabilities, the SUWPS’ intricate construction and delicate system housing makes fielding problematic. 
One possible solution to increasing filtration efficiency in a portable system is introducing nanoparticle filters. Carbon nanoparticles are lightweight, abundant and inexpensive.  Nanoparticles possess a large surface area and when combined with gold and/or silver ions are capable of destroying microbes, bacteria, viruses, mercury and other chemical contaminants.  Carbon nanotubes, which allow water to pass through while rejecting most salts, ions and pollutants, are another possibility.  While carbon nanotubes are effective at removing heavy metals, bacteria, viruses, cyanobacterial toxins and metalloids,  the health risks and environmental effects of carbon nanotubes require further study before implementation in water filtration.  Carbon nanotubes are effective in removing a wide range of contaminants, thus their use could replace multiple filters.  Multi-filtration capabilities paired with affordability, availability and compact size, makes carbon nanotube filter integration a technology worth integrating into DoD water security strategic plan.
Conclusion and Recommendations
HDIAC’s analysis provides the DoD an objective approach to emerging technologies in water filtration through breakthroughs in materials sciences. Current military water purification systems
require improvements in mobility and filtration capabilities to meet the needs of the warfighter. Carbon nanomaterials incorporated into existing systems and developed into new water
filtration systems will enable the DoD to ensure water security at FOBs and other DoD installations.
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