SSC-Natick Press Release
U.S. Army Soldier Systems Center-Natick
Public Affairs Office
Natick, MA 01760-5012
Contact: Chief, Public Affairs Office
Date: February 7, 2005
Project aims to clean, recycle dirty dish water
NATICK, Mass. -- Dump it on the ground or haul it away. Water sullied by food and soap from washing dishes in field kitchen sanitation sinks never had another chance until the Greywater Remediation and Recycling project started two years ago.
Cleaned and reused, the Army figures on cutting potable water consumption and the amount of greywater backhauling by two-thirds. With an estimated annual 20 million gallons of water now used nationwide for field sanitation, the Army also can expect to save money.
"It all goes back to the need for the Army to reduce logistics," said Chad Haering, a chemical engineer on the Equipment and Energy Technology Team at the Department of Defense Combat Feeding Directorate at the U.S. Army Soldier Systems Center here. "(Water) is the heaviest commodity they have and extremely hard and expensive to move, and we know from Iraq, can be dangerous to transport. Reducing the demand for the use of water is going to reduce the Army logistics footprint."
Other benefits are a healthier environment because food particles and stagnating water attract pests and spread disease, and less work for the kitchen crew since digging a grease trap for greywater is complicated, according to Haering.
Pots, pans, utensils and other dishes are washed, rinsed and sanitized in the field with a three-sink food sanitation center that consumes nearly 250 gallons of potable water daily. Wastewater is either poured onto the ground, or stored in a tank or bladder for disposal.
The team is working with two technologies on the commercial market that have for decades been used for industrial applications, such as ultra-filtration for car washes, but only in recent years been manufactured small and lightweight enough to be practical for the military, according to Haering.
Two different ultra-filtration systems were tested for use with the Food Sanitation Center during a training exercise at Fort Lee, Va., last August.
The Splitter XD from Infinitex uses spiral-wound membranes for a high surface area in a compact space while the system from Bristol International Corp. uses 5-foot-long, 1-inch-diameter tubular membranes. Water flows parallel to the semi-permeable membrane, and the shearing action helps to reduce fouling.
"(Ultra-filtration) is not as effective as reverse osmosis, but it's not meant for drinking water," Haering said.
A third product tested was a micro-distiller from Ovation Products Corp. Its vapor compression distillation process separates the water and impurities with a new technology allowing low-power consumption per gallon distilled in a compact package.
Both processes use a commercial filter to pre-screen suspended solids, are low or no-maintenance, and are as easy to operate as flipping a switch.
Water quality was sampled before and after processing during the test, and analyzed in 12 categories. Testing proved 85-90 percent of the greywater could be recovered, leaving 10-15 percent of it concentrated sludge for backhauling.
Besides the high percentage of remediation, the test showed a permeation rate of 15-20 gallons per hour, fast enough to allow remediation to finish before the next meal. Between-meal remediation also balances demand on the kitchen generator, Haering said.
After testing, the Bristol was dropped as a candidate because of its size and number of tubes, he said, but the Infinitex and Ovation are still in the running although they posted mixed results.
"Water coming out of the Ovation is extremely high quality, but it's too heavy and too fragile," Haering said. "The Infinitex is lightweight and rugged enough, but the quality is not quite good enough."
Fixes for both are on the way. He said Ovation is designing a lighter, more rugged system and will have a prototype this April while Infinitex will benefit if the U.S. Army Center for Health Promotion and Preventive Medicine relaxes its standards.
"The standards now are that only potable water be used for washing and rinsing, but as soon as you start washing, the water gets dirty. If you can continue to wash dishes in slightly dirty water, you can use this reclaimed water," Haering said. "It's good enough for washing and rinsing, but the sanitation sink would still use potable water to not compromise safety."
Greywater remediation and recycling is also finding a home in a future field kitchen.
Connected to Combat Feeding's developmental Field Feeding Advanced Sustainment Technology kitchen, a steam-powered greywater recovery system from Advanced Mechanical Technologies Inc. (AMTI) distills water to remove contaminants.
AMTI's unit slides underneath the sink and can be disconnected so it can be packed for transit. Its 10-12 gallon per hour flow rate is slower than desired, but the sanitation center's water demand may be lower to meet the requirement of between-meal remediation, said Tony Patti, a mechanical engineer on the Equipment and Energy Technology Team.
With the initial phase finished, the team will continue with a one-year effort if additional funding from the Environmental Security Technology Certification Program is approved, said Haering.
For more information about the U.S. Army Soldier Systems Center, please visit our website at: http://www.natick.army.mil.