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MEI Online: Reagents: Latest News: June 14th 2004


:: US EPA Confirms Efficacy of Virotec Technology in Remediation Trials at Gilt Edge Mine, South Dakota

Virotec International Ltd (ASX/ AIM: VTI) is pleased to provide to the market, information contained in a letter received from United States Environment Protection Agency (US EPA) that confirms the long term efficacy of ViroMineTM reagent developed from BauxsolTM technology. The letter and accompanying data tables summarise the findings to date of trials carried out at the Gilt Edge Mine Site which have been ongoing since 2001.

Executive Chairman, Mr Brian Sheeran explains "Virotec has patiently awaited the results of these independent trials for over three years and they exceed our highest expectations. At the Gilt Edge Mine site, Our technology is achieving excellent results in the field, in what we believe is potentially the world’s largest minesite remediation market, and we would draw attention to the following highlights of the letter from the USEPA:

US EPA states that ViroMineTM reagents may have several potential applications at the Gilt Edge Mine and possibly at other mine sites similarly affected by problems associated with acid rock drainage.

In particular, data from one single ViroMineTM application to some of the worst waste-rock encountered at the Site appears to indicate that the ViroMineTM Permeable Reactive Barrier remains active more than three years after the original treatment was carried out, and leachates continue to meet or exceed established water quality criteria for the Site.

The contents of the correspondence are based on findings from site trials conducted over a three year period (2001-2004) at the Gilt Edge Mine site - a 258 acre open pit, cyanide heap-leach gold mine in South Dakota - which has been placed on the National Priorities List for hazardous and toxic waste cleanup.

Other highlights include:

  • The concentration of the highly hazardous element arsenic (As) has been reduced from 35,000 to less than 5 parts per billion (well below the strict new drinking water standard of 10 parts per billion).
  • The extremely high concentrations of iron (21,000,000 parts per billion) and aluminium (1,200,000 parts per billion) were reduced to less than 50 parts per billion and have remained at very low concentrations ever since.
  • The concentrations of many other trace metals including: antimony (Sb), cadmium (Cd), cobalt (Co), copper, (Cu), chromium (Cr), lead (Pb), manganese (Mn), nickel (Ni), silver (Ag), vanadium (V) and zinc (Zn) were all reduced from potentially hazardous concentrations to concentrations that were near or below the analytical detection limits and well below discharge water quality standards.
  • The total dissolved solids concentration (i.e. salinity) was substantially reduced immediately and decreased further the longer the trial continued.
  • The concentrations of many ions such as sodium and sulphate, which are difficult to remove, have continued to decrease substantially the longer the trial has continued.

The Gilt Edge mine was developed in sulfidic (acid-generating) rock at the headwaters of cold-water fisheries and local water supplies. When the operator went out of business, they left behind 150 million gallons of acidic, heavy-metal-laden water in three open pits and millions of cubic yards of acid-generating waste rock that need cleanup and long-term treatment.

Going forward, the US EPA has directed that further studies be conducted to enable the USEPA to determine how Virotec’s upgraded range of products, including the recently developed ViroMineTM pellets, might be effectively used at the Gilt Edge Mine site and to acquire and assess quantitative data regarding metal-loading/sorption capacity.



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