The cuboid solution for CCR and mine water treatment
Liberty Hydro has developed ZVI Blue™ as a cuboid-shaped porous media to remove selenium, arsenic, mercury, chromium, thallium and other dissolved contaminants from discharge waters.
The media works together as a packed bed reactor in standard pressure tanks to provide water treatment solutions for CCR contact and drainage water, and discharge water from mining operations and industrial applications.
- ZVI Blue™ media is manufactured in a cuboid shape and uses zero valent iron adhered throughout a porous foam substrate.
- The media can be loaded directly into standard reactor vessels and, when exhausted, can be removed by vacuum truck.
- ZVI Blue™ media works as a packed bed reactor allowing water, for a predetermined retention time, to come in direct contact with the zero valent iron incorporated into the media.
- Zero valent iron creates a chemical reaction / electron transfer which reduces oxidized contaminants, like selenate and selenite, absorbing and removing contaminants from the effluent
- ZVI Blue™ media has worked effectively for a duration of 2 years in a mining application
- For other waters, the media is expected to have an active life of 9 months to 1 year, depending on the effectiveness of the pre-treatment system and the concentration of contaminants.
- The exhausted media can be disposed of in a regular (non-hazardous waste) landfill.
- The chemical reaction process creates dissolved iron in the effluent which has further beneficial effects of removing trace contaminants when the iron is oxidized and removed from the water stream.
- Pilot testing has validated effective removal of selenium at coal ash ponds, FGD purge waters, and mine waters.
- The focused application is for removing contaminants from power plant and industrial discharge water and for re-using mine water for irrigation and agricultural purposes.
- Laboratory and field applications validate the removal of other dissolved metals, including chromium, while research has shown the removal of pathogens suggesting a future application for the pretreatment of contaminated drinking water.
- The water in a coal ash pond can be stratified, with simple rainwater and surface water occupying the top layer of the ponds. Other technologies are reported to be struggling to treat simple surface waters with levels of 10 to 15 ppb of selenium, causing delays in the dewatering and treatment operation. Liberty Hydro ZVI Blue™ has been shown to be most effective at treating higher levels of contamination, likely to be encountered at deeper levels of the pond when encountering interstitial and pore water.
Alternative or Supplement to Bio Treatment:
- ZVI Blue™ technology can be used in place of biological treatment or as a supplement when biological treatment is employed in a treatment system.
- Biological treatment can create hidden and harmful effects by converting selenium into hard-to-detect organo compounds that readily bio-accumulate and cause detrimental effects to aquatic life.
- Source: The Role of Ultra-Trace Selenium Speciation Analyses and Ecological Risk Assessments. Brooks Applied Labs, posted January 12, 2107
- ZVI Blue™ media removes these potentially harmful forms of organo compounds, assuring better water quality in the receiving waters.
Representative Test Results for Selenium removal:
|Coal Ash/ Landfill||7 – 80 ppb||<5 ppb|
|Mine waters||20 – 100 ppb||<5 ppb|
|FGD Purge waters||300 – 1000 ppb||<10 ppb|
Note: ppb = μg/L
Full-Scale System Design:
(showing design for mine water application, following pretreatment with chemically enhanced sand filtration)
ZVI Blue™ Product Characteristics:
- Size of individual cuboid media: 1 inch x 1 inch x ½ inch, or smaller
- Weight of media in packed bed: 35 pounds per cubic foot / 5 pounds per gallon volume
- Operating temperatures: effectiveness achieved at broad range of water temperatures
- Longevity will depend on concentration and water quality, but 6 months to 24 months has been achieved
- Retention time can be extrapolated from other field data and can be pre-determined from pilot testing
- Effect on pH: the chemical reaction will raise pH, justifying pH adjustment between reactor vessels.
- Ideal inlet pH is 5.5 to 6; effluent prior to adjustment will be > 8.
- Media disposal: media is nonhazardous and can be disposed of in a standard nonhazardous landfill
- Storage: in dry place; wet media / premature disposal can be exothermic, so proper handling is required
- Side effects: reaction produces dissolved iron, meriting downstream iron removal which beneficially removes other trace contaminants
The information provides a guide to ZVI treatment. It is based on data and extrapolations and believed to be accurate, but does not constitute a guaranty or warranty. Liberty Hydro welcomes the opportunity to work with customers on solutions to their particular water quality. Together we can validate the suitability of the proposed treatment train.
Liberty Hydro, Inc. 1740 Union Carbide Drive, South Charleston, WV 25303