Polluted Mine Drainage Clean Up

By Dr. David McConchie
October 2000

The author is internationally acclaimed as one of Australia´s leading scientists in the new discipline of Engineering Geochemistry and Chief Scientific Consultant at Virotec Global Solutions, developing the Bauxsol™ technology over an eight-year period of extensive research.
As the Professor of Engineering and Environmental Geochemistry in the Centre for Coastal Management at Southern Cross University and a co-founder of the Centre for Research on Acid Sulphate Soils, Dr David McConchie is at the cutting edge of research into applied geochemistry. The analytical laboratory that he created at Southern Cross University is one of the finest geochemical analytical laboratories in an Australian University and the first to be fully self-funding and to receive Certified laboratory Practice accreditation (Licence No. CLP0052) conforming to AS/NZS ISO9002 and ISO-IEC Guide 25 standards.
For the past 20 years, he has examined innovative ways of using natural geochemical processes in the management of environmental problems and his work has focussed on the geochemistry of trace metals in sediment, water and biota; acid sulphate soils and acid mine drainage; early digenetic mineral transformation; trace element speciation in sediments; the influence of biota on trace element distributions in sediment and water; and the use of bauxite refinery residues in environmental remediation.

Queensland environmental technology company, Virotec International, is releasing treated water from a 14.5-hectare 1.5 billion litre mine tailings dam which the company´s new technology has cleaned of heavy metals and Acid Mine Drainage. (1)

The tailings dam (2) at the Mt Carrington mine in northern News South Wales was considered one of that State´s most urgent environmental problems as it sits in the catchment of the Clarence River.

Polluted mine drainage and pit lakes continue to be the mining industry´s worst and most enduring legacies as evidenced when 100,000 tonnes of cyanide-tainted water burst through a breach in a tailings dam in Romania in January this year. This failure was blamed for killing fish and livestock in Romania, Hungary, and Yugoslavia and spread 600 km south into the River Danube.

Dr David McConchie, Professor of Geochemical Engineering in the School of Resource Science and Management and First Personal Chair at Southern Cross University, affirmed that the cleaned water meets the most stringent Australian and New Zealand Environment and Conservation Council water quality guidelines for the Protection of Aquatic Ecosystems. (3)

The cleaned water is being released at the rate of one million litres per day. There is no longer a risk of contaminated water from the tailings dam overflowing into the Clarence River Catchment during heavy rain.

"I´ve seen and studied many of the world´s worst acid mine drainage problems and this is the first time in the world that such a large body of water contaminated with Acid Mine Drainage and heavy metals (4) has been cleaned to such strict environmental standards using a commercially viable, cost effective technology," Prof McConchie, who is also Virotec´s Chief Scientific Consultant, says. (5)

"The Virotec technology (6) has tackled one of New South Wales´ worst environmental problems, the 10-year-old Mt Carrington tailings dam, and the clean water can now be gradually released into the Clarence River catchment."

The new Virotec technology, trademarked as Bauxsol, is derived from bauxite refinery residues.

Professor McConchie said the chemistry of Bauxsol treatment involved a number of complex chemical reactions.

"Bauxsol modifies the pH of the water and simultaneously creates a change in the speciation of metals that then promotes their removal to the solids.

"Once the metals start to move to the solids they are removed from the water by the precipitation of new minerals and once precipitated into these mineral phases they are no longer available to the environment.

"I have worked with Virotec during the clean-up to verify the scientific data and consolidate treatment protocols – how to apply the Bauxsol, how much and how long it takes – so the technology can readily be applied to a host of other environmental problems," Professor McConchie said.

Virotec´s scientists are monitoring the cleaned and released water and the aquatic eco-systems of nearby Sawpit and Plumbago Creeks and early reports indicate a substantial improvement in water quality.

A Woodward Clyde report, DRAKE REGION – PLUMBAGO CREEK CATCHMENT STUDY (Sept 1994) is which local water quality was evaluated indicated Zinc metal readings as high as 25,000 parts per billion in Sawpit Creek and 400 parts per billion in Plumbago Creek.

"These water courses have been affected by years of acidic drainage. Mining caused some of this leaching but the area has naturally high, intrinsic zinc values," Prof McConchie said.

"Since we started the controlled release of the cleaned water, with a zinc component less than 50 parts per billion we have begun to flush the watercourses. Not just zinc but a wide range of trace metals.

Prof McConchie said Virotec welcomed the participation of government regularity authorities in the monitoring and who are conducting due diligence into Virotec technology.

Notes

  1. Acid Mine Drainage (referred to in North America as Acid Rock Drainage) occurs when sulfidic materials are exposed, through mining or other development activities, to oxygen and water. Water seeping through tailings dams, waste rock, or acid sulphate soils, carries acid into streams making the waters highly acidic. It may also contaminate ground water. Acid Mine Drainage kills plants and animals and inhibits bacterial decay of organic matter in water thus allowing large quantities of organic matter to build up in streams. The sulfuric acid also leaches toxic elements such as aluminium, copper, zinc, lead, arsenic, and cadmium. US mines produce about 2.7 million metric tons of acid a year and Acid Mine Drainage pollutes over 26,000 kilometres of streams. A similar problem exists throughout the world.
     
  2. Tailings dams are the most common devices for containing mine waste. Tailings disposal is a dangerous business with breaches of tailings dams occurring with unwelcome regularity. Tailings dams are serious problems –not only because the dams can collapse when the mine is active but also because they stay behind when the mine closes.
     
  3. The Australian and New Zealand Environment and Conservation Council (1992) recommends water quality guidelines for: aquatic ecosystems; drinking water; recreational water; industrial and agricultural water. The guidelines for aquatic ecosystems (Schedule A) are the most stringent.
     
  4. Heavy metals removed from the Mt Carrington project include; aluminium, cadmium, copper, iron, lead, nickel, and zinc. pH levels lifted from 5.2 to 7.26 milligrams per litre. Concentrations of other environmentally important components; silver, arsenic, chromium, nickel, selenium, mercury; were near or below target values before treatment and were reduced further by Bauxsol treatment.
     
  5. Prof McConchie went to government to further his research but was turned down three times. Putting his money where his month is after a lifetime of research Prof McConchie is a Virotec director. He is regarded amongst his academic peers as one of the world´s foremost authorities on the problem of Acid Mine Drainage. He was a finalist in the Australian Eureka Prize for environmental research in 1995 and 1996.
     
  6. Virotec holds the license for the worldwide marketing and distribution rights to its Bauxsol technology.
     
  7. TCLP tests (USEPA method) and compulsive exchange tests (Gillman & Sumpter 1986) show that less than two percent of the absorbed metals are released from Bauxsol sediment.

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