(WES-PHix® Stabilization Process)
WES-PHix® is a patented stabilization process that significantly reduces the solubility of certain heavy metals in solid waste streams by altering the chemical composition of the waste material. The process does not produce a solidified mass, unlike most other stabilization technologies.
The figure below illustrates the process. First, waste is fed at a controlled rate into a mixing device, such as a pug mill. The full-scale WES-PHix® process uses a pug mill with a capacity of 40 to 200 tons per hour. The stabilization reagent is then added to and mixed with the waste for about 1 minute. Once stabilized, the waste is removed by a conveyor from the end of the mixer. For some wastes containing cadmium, small amounts of lime must also be added. The WES-PHix® Process uses a proprietary form of soluble phosphate to form insoluble and highly stable metal phosphate minerals. Reaction kinetics are rapid; thus, no curing step is necessary. As a result, metal concentrations in the treated waste are less than toxicity characteristic leaching procedure (TCLP) regulatory limits. In addition, the use of small quantities of liquid phosphate reagent creates only a minimal increase in the weight of the stabilized waste.
Equipment requirements include a metering device for feeding the waste stream to the mixer, and a storage tank for the liquid reagent. Over-sized items such as boulders or wood debris require crushing or removal by screens before treatment. No posttreatment is necessary with this process. Treated residuals can be transported for final disposal with dump trucks or roll-off container vehicles.
This process was originally developed to treat municipal waste combustion ash containing heavy metals. The commercial-scale process has treated over 7 million tons of ash. However, laboratory treatability data indicate that the technology can also treat contaminated soils, slags, sludges, foundry sands, and baghouse dusts. Recent research indicates that the process is particularly effective at stabilizing lead, cadmium, copper, and zinc in a variety of media, as measured by TCLP and other laboratory leaching tests.
The WES-PHix® process was accepted into the SITE Demonstration Program in spring 1993. The demonstration, which was scheduled to occur at the Jack's Creek site in Maitland, Pennsylvania, has been postponed.
EPA PROJECT MANAGER:
Teri Richardson
U.S. EPA
National Risk Management Research Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
513-569-7949
Fax: 513-569-7105
TECHNOLOGY DEVELOPER CONTACT:
Mark Lyons
Wheelabrator Technologies Inc.
4 Liberty Lane West
Hampton, NH 03842
603-929-3403
Fax: 603-929-3123