Davis Street Landfill
Waste Management of Alameda County’s former Davis Street Landfill in San Leandro, California is the flagship of Waste Management’s Northern California operations. Beginning as a landfill in 1942, a portion of the site became an MSW transfer station in 1979 as the landfill closed. In 1990, a recycling facility was added to the transfer station site, serving 20 different Bay Area cities in achieving the required 75% diversion of MSW from landfills.
The closed 196-acre landfill site has a leachate collection system that maintains an inward gradient and produces about 60 GPM of leachate that goes to a treatment system prior to disposal. The system was originally designed using a stacking tray air stripper to remove methane from the leachate. Suspended solids and biofilm that is deposited on the air stripper trays is routinely cleaned from the unit to maintain efficient operation. Unfortunately, the stacking tray stripper design proved to be a maintenance challenge.
Patrick Madej, the Landfill Supervisor for the facility, saw multiple problems with the stacking tray design. "The gasket seals between the trays began to leak," said Patrick, "and a leak would be like a geyser. The trays would leak at the corners where the gaskets were joined or between the clamps where there wasn’t enough force to maintain a seal." Patrick also noticed that clamps weren’t adjustable, which just added to the problem. He tried using shims to tighten the clamps and resorted to putting non-curing silicone sealant on the gaskets, but the leaks continued. Routine cleaning was also a major undertaking. The stacking tray design required 2-3 people to lift the heavy trays, and the liquid and air piping had to be disconnected and reattached. Cleaning ended up taking a full day for at least two workers every three months.
Art Jones with SCS Field Services suggested that Patrick look into an E-Z Tray® (U.S. Patent Number 5,518,668) sliding tray air stripper from QED. The E-Z Tray’s patented sliding tray design uses a sealed stripper box with a removable end door and stripper trays that slide out on rails, much like oven racks. With no external tray seals and no need to disconnect piping for cleaning, leaks are virtually eliminated. The sliding trays in the E-Z Tray Model 6.4 that Patrick selected weigh just 40 pounds and can be handled with ease by one person. Best of all, Patrick found that he could replace his stacking tray stripper with an E-Z Tray unit that would mount on his existing skid and utilize his blower and control panel. With all these advantages, the retrofit made sense for Waste Management, and the results have been impressive.Patrick saw the benefits of the E-Z Tray design immediately. "I’ve never seen a leak from the E-Z Tray. The one-piece door seal makes a big difference – no gaps to create a leak. The knobs on the access door can be removed by hand, and they don’t even need to be very tight to make a seal." Cleaning time has been cut dramatically – it takes one person about an hour every 3-4 weeks to slide out the trays, pressure wash and replace them. Total cleaning labor has been reduced from about 65-80 hours per year down to just 12-16 hours.
"The E-Z Tray is a much cleaner system" says Patrick. "We don’t have to deal with leaks, so our treatment area always looks great." He’s now looking into purchasing a second set of trays for his system to minimize system downtime for maintenance.
For more information on how an E-Z Tray sliding tray stripper can save time and expense in your treatment application, visit www.qedenv.com/modeler where you can run the E-Z Tray Online Performance Modeler to estimate removal rates and find the right E-Z Tray model for your specific project.