In late 2012, MDD constructed and tested the Energy and Water Conservation System (EWCS), which successfully demonstrates the technology to recycle gray water from showers, sinks, etc. at Forward Operating Bases (FOB) for subsequent FOB reuse.
In recent years, the USMC identified a capabilities gap in the treatment of FOB wastewater. While potable water production operations are currently satisfactory, the USMC lacks gray water treatment capabilities within smaller bases. The goal of the EWCS was to save energy (by reducing transport costs) and improve safety (by reducing convoy sizes) by treating gray water in the FOB, and therefore reducing the volume of wastewater shipped to Main Bases for subsequent treatment. The EWCS allows for the gray water produced from showers, laundry, and non-kitchen sinks to be filtered, recycled, and used again. The EWCS is not intended to treat gray water to potable standards, but for reuse in showers, sinks, and laundry facilities.
The EWCS design features a comprehensive filtering system, composed of specially selected pre-filtration technologies for non-kitchen gray water treatment (including a basket strainer, sediment removal microfiltration, and ultrafiltration stages) combined with the innovate use of low pressure membrane filtration to treat BOD5 components of wastewater. The EWCS also features a chlorinator as the final stage of filtration, to prevent subsequent biological growth in the treated water storage tanks awaiting reuse. The EWCS is capable of providing up to of 8,000 gallons per day (gpd) of recycled water for non-potable water use.
MDD’s innovative use of low-pressure membrane filtration is the principal engineering achievement of the EWCS design. Typically, treatment of BOD5 components requires holding tanks for the chemical or biological reduction to occur. This process occurs slowly and therefore this standard method would prevent the EWCS from treating the gray water at the required rate of 5-6 gallons per minute. In treating BOD5 in gray water by using low-pressure membrane filtration, MDD removes the need for bulky chemical treatment tanks and achieves the required volumetric throughput. In addition, membrane filtration designs are typically used with high-pressure systems, such as saline removal and normally require rigid piping and high-energy pumps to operate. However, the use of a low-pressure membrane system reduces the size and mass of the EWCS construction, thus allowing for a compact, lightweight design, and averting the energy requirements of a high pressure pumping system.
MDD’s EWCS technology demonstrator treats water to USMC gray water reuse standards at approximately 6 gallons per minute. The power required to operate the EWCS is less than 18 amps at 110 Volts, single phase. The EWCS weighs approximately 1,200 pounds and is small enough to be transported and handled via HMMWV M116-A2 trailer and light forklift. Ultimately, the EWCS’s effective in-FOB gray water treatment capability, combined with its small size and low power requirements, significantly improves the self-sufficiency of Forward Operating Bases and reduces the USMC’s power and logistical requirements in maintaining expeditionary forces.