A Marine disconnects a hose from a water pump at a water purification site during the 11th Marine Expeditionary Unit's Field Exercise.
While ongoing work on water purification technologies has broad applications across different military roles, certain projects and goals have significant implications for SOF units.
There are a number of priorities that underpin government and industry efforts in water purification for the military. Water is clearly an essential part of logistics, but it brings with it a number of challenges. It can be burden some and expensive to transport large amounts of water.
It can also be dangerous. with convoys an obvious target for attack. In this context, technologies that allow users to safely exploit local sources or improve efficiencies have clear advantages. Reducing the logistics burden has obvious appeal to SOF users.
Particular requirements will vary depending on the branch or unit in question, but in general, smaller groups of personnel - such as SOF operatives in the field - will often have less infrastructure to hand than many users in the broader Army.
"Regular" military users look at it "where they have a bunch of infrastructure. either resources of people or supplies around them that help them get their job done." said Joe Weiss. VP of programs and engineering in the Engineered Solutions division of Outdoor Venture, a manufacturer of a range of purification systems and other technologies.
"Special forces look at it a little bit differently and say ‘hey. I don’t have all this infrastructure. I want a capability that works for my guy who's sitting right here without anybody else around him." he explained.
Logistical and operational demands were key to SOF requirements, said Ed Atchley, owner of Aspen Water, a manufacturer of purification systems in a variety of sizes.
"If our systems are smaller, lighter, use less energy, and [are] easy to maintain or in many instances self-diagnosing, you take [out] a lot of the training required on the use of the systems and it fits the mission."
There are a range of projects underway in both government and industry circles that have implications for SOF users.
The US Army Tank. Automotive Research, Development and Engineer ing Center (TARDEC), for example, is working on a program called the Small Unit Water Purifier (SUWP). which is aimed at supporting groups of roughly platoon level in size This would make it the smallest such purifier in US Army service.
Currently. that distinction belongs to the Lightweight Water Purifier (LWP), which can be transported in the back of an HMMWV and purify 125 gallons per hour (GPH) of freshwater and 75GPH of saltwater. The SUWP would be considerably smaller than the LWP; It would be capable of two-person lift, unlike the LWR which requires four persons.
The SUWP would be relatively simple to operate, so there would not be a need for a specialist operator to use it. The system would be manually operated, but very simple to use, according to Bob Shalewitz, team supervisor on the water treatment and handling equipment team a TARDEC.
"You don’t have a lot of [complex] tasks for the operator... I think with [an] automated system, you push a button and it works, but if anything goes wrong, they tend to not to be able to troubleshoot the system easily. So, we’ve selected unit processes in the system that are fairly simple to operate and maintain."
The US Army uses a number of different systems of varying sizes that purify water and make it potable. For example, it utilizes Reverse Osmosis Water Purification Units (ROWPUs), in two variants, one that produces 3.000GPH from freshwater and 2.000GPH from saltwater, and another that produces 600GPH from saltwater and 900GPH from freshwater.
It also has the Tactical Water Purification System (TWPS), which can produce 1.200GPH from saltwater and 1.500GPH from freshwater. All of these systems use a similar base technology, reverse osmosis (RO), in which a semipermeable membrane removes bacteria, particles and other contaminants from the water, in order to make it fit for consumption.
While there are clear logistical advantages to having a relatively small water purifier for SOF and other users, there are challenges in adapting these processes to a smaller system, for example in the area of "pre-treatment".
This takes place ahead of RO, and aims to remove any contaminants - such as dirt or microorganisms - that build up on the membranes in a problem called “fouling”. Many smaller systems use standard cartridge filters for pre-treatment, which need to be replaced frequently. Instead, the Army is looking at incorporating sophisticated pre-treatments using ultra- or micro-filtration, which remove high levels of fouling.
"We’d love to get a pre-treatment that is as simple as a media filter or a cartridge filter, but gives you the water quality of an ultra filter or a micro filter," said Dr. Jay Dusenbury, senior technical expert at TARDEC’s Force Projection Technology arm.
"That's hard to do, without having to change out filters or clean things. Soldiers aren’t going to want to use a system that they have to shut down every five minutes and clean."
A second challenge surrounds the pumps. The army wants to use high- pressure pumps with energy recovery, which maximizes efficiency. Most of those types of pumps are currently in a larger size than would be required in such a small solution.
"There are a few technical areas that we’re looking at, trying to get improvements in: the pre-treatment. and the energy recovery for a small system like this," Shalewitz told SOF. The system would be modular, he said. This would allow for greater flexibility, something that would appeal to Special Forces users, who may need it in a variety of scenarios.
There would be a module using RO, which would be needed to treat saltwater, as well as any other water when there are particular concerns about contaminants. There would then be a separate, ultra-filtration module: as well as conducting pre-treatment, this could also be used to make most sources of freshwater potable, as it filters water to a high level in its own right.
The Small Unit Water Purifier being developed by TARDEC could have implications for Special Forces users thanks to its relatively small size and modularity.
The systems then add chlorine, in order to prevent recontamination of the water. There would also be a separate power module, which could be taken as required. "If they have power, all they need is that [ultra-filtration] module. If they don’t have power, they can take the power module and the freshwater module," said Shalewitz.
"If they do need to treat seawater, or if there’s another contaminant of concern that [ultra-filtration] won’t remove, they can take the RO module as well." The modular design meant that if "they have a freshwater source and have power, they only need to take one of the modules with them, or procure one of the modules. If they’re on saltwater or brackish water and they don’t have power, they can take all three pieces. So, they can mix and match, depending on what their mission is."
It could be worth using the ultra-filtration model even when the water source appears safe, Shalewitz explained. "Even if they were in a safe house, where they may actually have access to some sort of municipal water, just to ensure the safety of it they would run that through the pre-treatment module as well, just to double check that it’s purified," he explained.
The pre-treatment side would be a major focus of research in the coming years, with ultra-filtration or micro-filtration technologies replacing the current media or cartridge filters on smaller purifiers, said Kevin Sofen, business development manager at Darley, a maker of purifiers.
The use of such technologies would make the filters completely autono mous (as the cartridges do not need to be changed) and eliminate the need for cleaning or disposing of the cartridges. “The biggest breakthroughs we’ll see in the next few years will be in the pre-filtration technology that optimizes the RO membranes for these types of small water systems,” he said.
TARDEC has built an SUWP demonstrator based on “the best of what’s commercially available right now,” Shalewitz noted. This is currently with the 25th Infantry Division in Hawaii, and will be used in Pacific Pathways 2017. It will be some years until the system will be ready to field, with TARDEC looking to around the 2019/20 timeframe for a finalized design.
"Our goal is to get it into troops’ hands and get some feedback on what they like, what they don’t like, so that as the program moves forward we can modify some of our solution sets to be more applicable to their needs." Shalewitz explained.
TARDEC is working on a number of other projects with broad military applications. One of these is removing water from atmospheric humidity. This is a challenging area, but would meet the goal of producing water near where it is needed; atmospheric humidity is of course widely available.
As part of its work in this area, TARDEC has built a trailer-based system that can produce 500gal of water per day from atmospheric humidity, said Dusenbury.
However, processing the necessary amount of air and taking it from vapor to liquid requires a high amount of energy.
While an RO system needs about 5-10 watt-hours per liter, condensation sucks up around 600 watt- hours per liter. "There’s not a lot of benefit to producing water from air if you have to move more fuel to the site than the water you actually produce," Dusenbury said.
TARDEC has therefore sought to maximize the water to fuel ratio. It has also looked to expand the “environmental envelope” of the technology as widely as possible, so that it can be used effectively in drier environments alongside naturally humid areas.
An important aspect of purifying water is easy to overlook: the taste. Water can be potable but still be unpleasant to drink. One of the most obvious problems is chlorine, Dusenbury said here has been a great deal of work carried out to understand what the right chlorine concentrations are, and how they can be placed into a palatable range.
"Now the standard is two parts per million at the production point, but it is allowed to drop to one part per million through the distribution and consumption of water," he explained. A second consideration is temperature. There have been efforts to provide chilled water, but "it’s one of the things you tend to trade off with weight", Dusenbury said.
There are other factors, too, such as mineralizing water to increase the mineral content, and ensuring it is not stored for too long a time at too high a temperature in storage and distribution systems, such as tanks and bags. However, palatability is not a major focus of the organization, Dusenbury noted.
Another system in development with SOF applications is Water in a Box (WiaB), an integrated purifier, monitoring and bagging system. The first two units are fielded, though another system is being developed by Outdoor Venture along with Darley, which is providing a small purifier.
WiaB is aimed at small groups of soldiers outside of the broader support loop, said Weiss, and therefore has SOF applications. "Water in a Box is an integrated system of purification capability, and then distribution and bagging capability with monitoring capability," he explained.
This integrated approach would appeal to users such as SOF, he said, as it provides water purification and also monitors the quality of the end product. A group of SOF operatives would "want purified water [and] they want to know it is the right water - there’s nothing wrong with it - in a way that they don’t have to spend much time on."
The water quality of WiaB would be monitored remotely, over a network, Weiss said, something that brought with it a number of challenges around cybersecurity. “These guys out there are a node on the network, and they’re trying to report back on their quality measurements- they want it to just happen, and then someone looks it at and says "everything is good’, or they have some smart tool that tells them that it’s good."
A major area of research in water purification more broadly is focused on gray water: reusing water from showers or laundry services. Supplying wa ter to bases can create huge logistical costs, as well as dangers surrounding the transportation.
These demands led to the creation of the Shower Water Reuse System (SWRS), which is manufactured by Outdoor Venture. SWRS can take 12,000 gallons per day (GPD) of shower or laundry water and turn it into 9.000GPD of potable water that can be used again for the same functions.
The SWRS is designed for bases of around 150 personnel, said Weiss, though Outdoor Venture is working on a smaller version that can be used for groups down to about 75. This would have SOF applications, he said, up to a point.
"That’s for a special kind of special operations, where they tend to have a forward operating base or command outpost. They’re more entrenched." Overall, however, purification technology has come a long way, Weiss said, and looks set to continue evolving in ways that could benefit SOF users.
"You’re within a decade of in effect creating small purifiers that are fully integrated, and effectively pop out of a bag that you can put in your canteen."