RNS Number:6432ZVirotec International Ld10 June 2004 US EPA...

RNS Number:6432Z
Virotec International Ld
10 June 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 this week from United States
Environment Protection Agency (US EPA) that confirms the long term efficacy of
ViroMine(TM) reagent developed from BauxsolTM technology. The letter and
accompanying data tables were provided by Mr. Ken Wangerud, Remediation Project
Manager, Superfund Remedial Program, USEPA - Region 8. They 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:

- All the trials followed US EPA protocols and no-one was allowed access
to the Site unless accompanied by US EPA representatives

- US EPA is evaluating cost-effective options for site remediation at
the Gilt Edge Mine consistent with the evaluation criteria in the US EPA's
National Contingency Plan.

- US EPA states that ViroMine(TM) 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, the Trench Trial data (Table 1) from one single ViroMine(TM)
application to some of the worst waste-rock encountered at the Site appears
to indicate that the ViroMine(TM) 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.

- Additionally, in 2003 an electron beam microprobe examination of a treated
waste rock sample showed evidence of sulfide encapsulation."

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.

HIGHLIGHTS FROM US EPA FINDINGS

Substantive ongoing 3 year results from the Permeable Reactive Barrier trial
(Table 1) show that the leachate pH was neutralised from 1.93 to 7.9; other
highlights include:

1. 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).

2. 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.

3. 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.

4. The total dissolved solids concentration (i.e. salinity) was substantially
reduced immediately and decreased further the longer the trial continued.

5. 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.

Substantive ongoing results from Waste Rock Remediation trials (Table 2) wherein
leachate pH was neutralised from 1.92 to 7.21 and highlights include:

1. The concentration of the highly hazardous element arsenic (As) has been
reduced from 23,000 to near or below the analytical detection limits and
well below discharge water quality standards (well below the strict new
drinking water standard of 10 parts per billion).

2. The extremely high concentrations of iron (19,000,000 parts per billion)
and aluminium (1,400,000 parts per billion) were reduced to near or below
the analytical detection limits and well below discharge water quality
standards.

3. The concentrations of many other trace metals including: antimony (Sb),
cadmium (Cd), cobalt (Co), chromium (Cr), lead (Pb), 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.

4. The total dissolved solids concentration (i.e. salinity) was substantially
reduced.

Substantive results from "in situ" Pit Lake Treatment trials (Table 3) wherein
leachate pH was neutralised from 2.59 to 7.09 and highlights include:

1. The analysis of water showed a significant improvement after just 42 days.

2. The concentrations of many trace metals including: aluminium (Al), chromium
(Cr) and lead (Pb) were reduced from potentially hazardous concentrations
to concentrations that were near or below the analytical detection limits
and well below discharge water quality standards.

3. The total dissolved solids concentration (i.e. salinity) was reduced.

4. The concentration of sulphate, which is difficult to remove, was decreased.

Substantive results from ViroFilter Passive Treatment trials (Table 4) wherein
leachate pH was neutralised from 4.47 to 8.38 and highlights include:

1. The analysis of water showed that passive filter treatment could produce
even better quality water than a direct addition "in situ" treatment.

2. The concentrations of many trace metals including: aluminium (Al), cadmium
(Cd), cobalt (Co), chromium (Cr), iron (Fe), lead (Pb), nickel (Ni), were
reduced from potentially hazardous concentrations to concentrations that
were near or below the analytical detection limits and well below discharge
water quality standards.

3. The high concentration of manganese (10,263 parts per billion) was reduced
to less than 3 parts per billion.


. 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 ViroMine(TM) pellets, might be effectively used
at the Gilt Edge Mine site and to acquire and assess quantitative data regarding
metal-loading/sorption capacity.

Full text of the letter from the EPA will be available at www.virotec.com.

For further information please go to www.virotec.com or contact us on +617 5530
8014.

Table 1: ViroMine(TM) Waste Rock Trench Data

Analyte - Units Control 2003 Result 2001 Result 2002 Result 2003
pH 1.93 7.9 7.96 N/A
Acidity (mg/L as CaCO3) 49,000 4