By Alan M. Weiss
Summary: In military operations, great emphasis is placed on mobilizing potable water treatment capabilities quickly. Equally as important is finding the right dynamics to make this possible in a portable unit. The following discusses a multi-filtration/UV purification system acquired by the Turkish Navy.
When planning for a portable purification emergency, you’re never sure what the water source will be. Therefore, versatility is a prime consideration in design. When the challenge water is seawater, reverse osmosis (RO) works but the capacity may be limited by size and available power requirements of a client’s specifications. For fresh water sources, the production rate can be higher, but there are numerous contamination challenges to anticipate. If both RO and filtration technologies are incorporated into the same mobile container, it’s possible to use both capabilities to achieve the maximum flexibility in performance demands.
One particular model produces potable water from seawater at 600 gallons per hour (gph) up to 1,500 gph from fresh water sources. The first such unit was delivered to the Turkish Navy (Special Operations) just prior to the devastating earthquake that shook the country in 1999 and proved a valuable asset in relief efforts. The specifications for this system are those initially specified by the U.S. Army for its latest prototype purification system.
The system for the Turkish Navy included an all-weather housing that can be heated or air-conditioned, is fully insulated and can run during adverse weather conditions. The desalination system will handle up to 50,000 parts per million (ppm) of total dissolved solids (TDS)—very high, but frequently encountered there. Keep in mind, the average salinity of seawater ranges between 32,000 ppm to 35,000 ppm, depending upon the source. Many seawater desalination systems are designed to handle up to 36,000 ppm with optimal performance.
This unit was delivered with a customized trailer for ease in mobility; however, it’s also easily moved by helicopter, can be placed on the back of a flatbed trailer or can be fixed in place on its own platform. Fixed-base water purification modular platform systems using the following design process potable water from all fresh water and seawater sources from 600 up to millions of gallons per day (gpd), with mobile desalination units—transportable via backpack, dolly or trailer—available with production rates as low as 75 gph and solar-powered capabilities up to 6,000 gallons per day (gpd).
While industry, municipalities and disaster relief efforts may employ similar desalination technology, the desalination series discussed here is more of a military specification. They’re manufactured in mobile configurations, fixed-based configurations or modular components that can be assembled to make larger (municipal) systems. The desalination series is comprised of a three-component system—basic prefiltration to eliminate most input problems that hinder typical RO systems, the latest technology in thin-film composite RO membrane separation for purifying water at extreme pressures, and a multi-filtration/ultraviolet (MF/UV) configuration that incorporates a 1-micron absolute filter with a multi-media formulation and UV disinfection to improve taste significantly.
Four modes of operation
The desalination series and the mobile units can function in four different modes of operation. This four-mode series provides for the purification of drinking water through the most cost-effective method applicable to the type of source water encountered. In doing so, it minimizes maintenance and operation costs as well as extends the life of the RO sub-system and its filtering processes.
Very simple controls will initiate any mode or sequence of operation. In the first three modes of operation, the initial system separator/sand filter can either be included or excluded from the process depending on the condition of the source water.
Mode 1: Water that’s not brackish, seawater or NBC (nuclear, biological or chemical) contaminated water is processed directly by the MF/UV portion of the system following prefiltration up to 825 gph. This process will greatly reduce the parasites, hazardous metals, disease-causing organisms, toxic chemicals, chlorine, bad taste, odor, bacteria and viruses that may be present. This process provides high quality drinking water through a simple-to-operate, low-maintenance, field-tested system and produces no wastewater stream.
Mode 2: Brackish, seawater or NBC-contaminated water is processed first through the RO, with that output water being processed by the MF/UV component. This process provides high quality drinking water from any source.
Mode 3: Brackish, seawater or NBC-contaminated water can be processed solely through the RO. This process provides acceptable drinking water from any source.
Mode 4: Fresh water can be processed directly by both the MF/UV and the RO components of the system simultaneously up to 1,500 gph. This process provides both high quality drinking water and acceptable drinking water. This mode provides for almost twice the normal system capacity.
Weighing the options
The desalination series can be delivered either as mobile equipment or fixed-base systems. Mobility in smaller units can either be on rolling stock (i.e., dollies) or platforms mounted on trailers. Smaller units can even be carried in special backpack designs. Mobile options also include all-weather enclosures with trailer, truck or container compatibility. Options available include self-contained power sources and NBC capabilities.
The desalination series’ concept is to provide both modularization for increasing or decreasing production requirements as well as split component modes of operation for more efficient operations. These units are expected to draw raw water directly from any source—fresh water, brackish water or seawater (with capabilities up to 60,000 ppm). The unit has a suction lift of 10-to-25 feet at distances up to 100 feet from the source. The distribution pump doesn’t have any lift rating. The system will run approximately 23 hours per day from seawater sources and closer to 24 hours per day from fresh water.
These units aren’t designed for sub-zero weather without being properly housed and, therefore, there’s no need for insulation in the basic unit. They incorporate open-air flow and don’t need air conditioning. Modules are easily accessible for maintenance and component replacement. The system can include its own diesel power source with sufficient power not only to run this equipment but to include area lighting and power for other tangential equipment and/or upgrades. This power unit can be mounted on the operating platform.
As special emphasis is placed on mobile equipment in military applications, the above-mentioned portable purification system is either mounted on its own platform or configured in rolling cabinets, in a lightweight design that make it easily transportable by land or air. The platform can be placed on a trailer bed or other vehicle beds. All components will meet ANSI, USEPA, OSHA and WHO standards/specifications.
About the author
Alan Weiss is president/CEO of Global Water Technologies, Dallas, Texas, a division of AMW Marketing Services Inc. The company was founded in 1990 and Weiss, a management consultant, bought it in 1996. He holds a bachelor’s degree from the University of Miami and has been president of six companies from agriculture to finance. Weiss can be reached at (214) 678-9866, (214) 678-9811 (fax) or email: [email protected].