Credit: InterClean Equipment
This diagram shows a passive washwater recycling system for transit buses.
Almost 180,000 waste collection, transfer, and recycling vehicles operate in the U.S., and they all need to be washed regularly, usually weekly. Each cycle requires close to 150 gallons of water. Add to that all of the cars, vans, pick-up trucks, service bodies, and construction equipment that state and local governments own, and you get a huge expenditure of water.
Reclaiming washwater cuts per-wash consumption by 80% to 90%. But achieving return on investment isn’t as simple as installing recycling components and watching the water bill shrink. Whether the extra equipment is a good investment depends on vehicle types, maintenance requirements, and—first and foremost—volume.
More washes, faster ROI
“Say you’re washing 20 vehicles once a week. That’s about 2,000 washes annually,” says Les Gale, North American sales manager for InterClean Equipment Inc. in Ypsilanti, Mich., U.S. distributor of Finnish heavy-duty wash systems for trains, buses, airplanes, mining, and military equipment whose public customers include the Regional Transportation Authority of Southern Nevada. “Given the expense of putting in pits and other equipment, it may take 20 years to break even.”
The table below shows the breakeven point for various scenarios.
“There’s a fiduciary responsibility, but cities often have green goals as well,” says Gale. “Sometimes the wise use of resources is simply the right thing to do.”
Both rationales, financial and environmental, are found at Deffenbaugh Industries Inc. near Kansas City, Kan., which provides commercial and residential waste disposal, collection, transportation, and recycling services. The company washes about 120 trucks a day, five days a week, at about 200 gallons per wash. Most is recycled, saving an estimated 20,000 gallons daily.
“We only use freshwater (the industry term for nonrecycled water) for soaping and final rinse—about 10 gallons,” says Facilities Manager Bob Rieke. “We’re saving money and meeting EPA regulations, and we’re also in the recycling business! It’s good to know we’re part of the solution.”
Like a standard car wash, the drive-through wash bay can presoak trucks before scrubbing them with spinners. Vehicles are parked over a long, fairly shallow trench into which solids and water flow. The sediment settles to the bottom and the washwater is recirculated with minimum filtration, a process called passive recycling (see diagram on page 21) that’s becoming much more common in the U.S. than the alternative: active recycling. Active recycling uses reverse osmosis filtration to return water to near-fresh purity, an energy-intensive process that requires large holding tanks.
Deffenbaugh cleans out the 6-by-100-foot pits with vacuum trucks about every 1,000 washes, a process that takes about four hours, and hauls the debris to a landfill nearby.
Municipal facilities fall near the other end of the scale.
“A public works department might have two pumps and three or four spray bars,” says InterClean Sales Engineer Chris Leineke. “If they’re washing salt trucks, or have a lot of vehicle variety, they’ll need more pumps and spray bars and maybe even a customized system, which will increase costs.”
Due to the highly saline effluent generated, facilities dedicated mainly to salt truck and dump bed maintenance may want to forego recycling. “Recycling doesn’t significantly reduce salinity and washing with salty water causes corrosion,” he says.
A standard vehicle-wash system is about $145,000, not including the building. Adding water reclamation brings the same system to about $175,000, the biggest expense related to building the solids pit.
Incorporating recycling into a new facility is much cheaper than retrofitting an existing wash bay. Almost 75% of new facilities include recycling capabilities.
“The only misconception about recycled water is that it’s easy,” says Leineke. “You need a carefully designed system, and there is some initial expense. But more and more, our customers understand what they’re getting into.”
Angus Stocking is a licensed land surveyor who has been writing on infrastructure topics since 2002. E-mail firstname.lastname@example.org.
Freshwater, or non-recycled water, isn’t free; but neither is the system necessary to recycle the water for future washing. This chart crunches the numbers.
Credit: InterClean Equipment Inc.