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SITE Technology Profile - Emerging Technology Program
November 1994 - Completed Project
TECHNOLOGY DESCRIPTION:
The Atomic Energy of Canada, Limited (AECL), process uses
chemical pretreatment
and ultrafiltration to remove trace concentrations of dissolved metals from
wastewater
, contaminated groundwater, and leachate. The process selectively removes metal
contaminants and produces a volume-reduced water stream for further treatment
and disposal.
The installed unit's overall dimensions are 5 feet wide by 7
feet long by 6 feet high.
The skid-mounted unit consists of 1) a bank of 5-micron cartridge prefilters, 2) a
feed
conditioning system with polyelectrolytes and chemicals for pH adjustment, 3) two
banks of hollow-fiber ultrafilters, 4) a backflush system for cleaning the membrane
unit, and 5) associated tanks and instrumentation.
Wastewater enters the prefilter through the feed tank, where
suspended particles are
removed from the feed. The filtered waste stream is then routed to conditioning
tanks
where the solution pH is adjusted. Water-soluble macromolecular compounds are
then added to the wastewater to form complexes with heavy metal ions. Next, a
relatively high molecular weight polymer, generally a commercially available
polyelectro-lyte, is added to the wastewater to form selective metal-polymer
complexes at the desired pH and temperature. The necessary polyelectrolyte
quantities depend on the metal ion concentration. Therefore, separated metal
ions should generally be in the parts per million (ppm) range.
The treated waste stream then passes through a cross-flow
ultrafiltration membrane
system by way of a recirculation loop. The ultrafiltration system provides a total
membrane surface area of 265 square feet and a permeate rate of about 6 gallons
per minute (gpm). The membranes retain the metal complexes (concentrate), while
allowing uncomplexed ions to pass through the membrane with the filtered water.
The filtered water is continuously withdrawn, while the con-centrate stream,
containing most of the conta-minants, is recycled through the recirculation loop
until it meets the target concentration.
After reaching the target concentration, the con-centrate
stream is withdrawn for
further treat-ment, such as solidification. It can then be safely disposed of. The
clean filtered water is discharged.
WASTE APPLICABILITY:
The process treats groundwater, leachate, and surface runoff
water contaminated
with trace levels of toxic heavy metals. The process also treats effluents from 1)
industrial processes, 2) production and processing of base metals, 3) smelters,
4) electrolysis operations, and 5) battery manufacturing. Potential applications
include removal of metals such as cadmium, lead, mercury, uranium,
manganese, nickel, chromium, and silver.
The process can treat influent with dissolved metal
concentrations from several
ppm up to about 100 ppm. In addition, the process removes other inorganic
and organic materials present as suspended or colloidal solids. The sole
residue is the ultrafiltration concentrate, which generally constitutes 5 to 20
percent of the feed volume.
STATUS:
The AECL process was accepted into the SITE Program in 1988.
During initial
bench-scale and pilot-scale tests, the AECL process successfully removed
cadmium, lead, and mercury. These results were used to design and construct
the mobile unit.
The mobile unit has been tested at the Chalk River
Laboratories and a uranium
mine tailings site in Ontario, Canada. The field demonstration indicated that
process water characteristics needed further study; pretreatment schemes
are being evaluated. The mobile unit, which is capable of treating influent flows
ranging from 1,000 to 5,000 gallons per day, is available for treatability tests
and on-site applications. A technology bulletin (EPA/540/F92/002) is available.
FOR FURTHER INFORMATION:
EPA PROJECT MANAGER:
John Martin
U.S. EPA
Risk Reduction Engineering Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
5135697758
Fax: 513-569-7676
TECHNOLOGY DEVELOPER CONTACTS:
Leo Buckley
Atomic Energy of Canada, Limited
Waste Management Systems
Chalk River Laboratories
Chalk River, Ontario, Canada
KOJ IJO
6135843311
Fax: 6135841438
Phil Campbell
AECL Technologies
9210 Corporate Blvd, Suite 410
Rockville, MD 20850
800-872-2325
Fax: 301-417-0746
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