Environmental Cleanup Challenge - Uranium Recovery and Soil Cleanup

by Rich Kimura - Date: 2006-12-31 - Word Count: 549 Share This!

The plant site was located in the sagebrush-covered desert of eastern Washington, and had 8 acres of large surface impoundments, or lagoons, filled with a blue-green solar-concentrated chemical solution. The lagoons were plastic-lined. These had accumulated 6 million gallons of liquid wastes for 30 years. Some soil contamination occurred when the lagoons leaked decades ago, and the lagoons contained a lot of sand and debris mixed with the liquid. The company was dedicated to cleaning up this mess and hired me to clean it up. I designed a large-scale uranium recovery and cleanup process that was operated for 7 years. A total of 6 million gallons of concentrated liquid wastes were cleaned up, and over 1 million cubic feet of soil were treated or disposed. This article briefly tells how this environmental cleanup process worked.

Uranium was selectively recovered from liquids, soils, and sludge containing metal precipitates, inorganic salts, sand and silt fines, debris, other contaminants, and slimes, which are very difficult to de-water. Chemical processes such as nuclear fuel manufacturing and uranium mining generate enriched and natural uranium-bearing wastes.

At the head end of this process was a floating dredge which retrieves liquids, sludge, and slimes in the form of a slurry directly from the surface impoundment at 600 gallons per minute. The dredge was equipped with a 100 horsepower sludge pump. The slurry was screened, passed through a grinder/shredder, and pumped into a 12,000 gallon feed tank. Debris from the screens are collected and disposed. The slurry was mixed in the feed tank with a turbine mixer and re-circulated to further break down the particles and enhance dissolution of uranium.

The brown was then heat treated by direct steam injection, to heat it up to 160F. The uranium was then made soluble by using a mild bleach (sodium hypochlorite) solution) strike that oxidized all of the uranium. The sodium hypochlorite oxidizes and dissolves any U(IV) present by converting it to U(VI). In addition, the heavy metal contaminants are not extracted into the liquid phase as would normally occur with aggressive oxidants such as nitric acid. Cellulose powder had to be added as a non-reactive filter aid to help filter slimy sludge to give body to the slurry. The cellulose did not react with uranium, which occurs with the use of diatomaceous earth or other inorganic filter aids. How did this all get figured out? By hard work and trial and error in the lab! Letting the data speak for itself was the key to success.

The slurry was pumped into 80 cubic foot recessed-chamber filter press that is also pre-coated with cellulose, and was then de-watered by a pressure cycle-controlled double-diaphragm pump. The clear filtrate was pumped through bag filters to a 12,000 gal filtrate collection tank.

The filtrate was processed batch-wise, and uranium was removed from the solution by special precipitation and filtration. The process was a clear success and recovered 3 metric tons of enriched uranium. The dried solids could be safely disposed. The process was patented and can now be used commercially wherever uranium-contaminated soils and sludge exist.

After seven years, the cleaned and removed lagoons were a big relief, and there was great joy to see the land returned to its natural condition. This was only possible with management support and cooperative working relationships with state and federal regulators.

Related Tags: energy, environment, recovery, power, waste, nuclear power, nuclear, uranium, cleanup, rich kimura

About Rich Kimura:

Rich Kimura is a freelance writer, married father of 4, chemical engineer, and entrepreneur. He has authored numerous technical papers, has 1 patents and 2 patents-pending, and 24 years experience in the nuclear and chemical industries. Rich started 6 micro-businesses, received financial counseling training by Crown Financial, and teaches on both subjects. To see more free tips and sharing of personal experiences in home businesses, work, money, finances, relationships, spirituality, and other topics, visit Cirrovista at www.Cirrovista.com

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