Case Study

Management of acid mine drainage (AMD) and other mine-influenced water has traditionally represented a significant challenge to mining companies around the world.

Clean&Recover has successfully trialled its ElectroClear technology to treat and clean AMD supplied from mine sites including:

• Mt Morgan
• Texas (near Stanthorpe)
• Mungari
• Mt Carlton
• Rio Tinto US site
• Maurliden (Sweden)

Participating mines are interested in exploring what they can do with mine-influenced water.  They want to know if they can extract the metals dissolved in the water, and whether there is anything better than traditional lime or caustic soda treatment.

ElectroClear offers mining and industry a demonstrated alternative solution to help meet these strategic and operational goals.

Demonstration of ElectroClear Acid Mine Drainage Technology: Boliden AB Sweden

Acid Mine Drainage (AMD) and other mine-influenced water has traditionally represented a significant management challenge to mining companies globally.

Clean&Recover partnered with Boliden AB to demonstrate the ElectroClear AMD technology™ for treating AMD at Boliden’s closed and open mine sites. The patented ElectroClear AMD technology™ uses electrodialysis to remove sulphates from AMD. ElectroClear AMD technology™ precipitates metals from the drainage for commercialisation and cleans AMD water so that it can be used on-site or discharged to the environment. The technology uses electricity rather than alkaline chemicals (such as lime or caustic soda) to neutralise the acidity in AMD.

In April and May 2024, Clean&Recover worked with Boliden’s local staff to demonstrate the plant on AMD from two mines.

In processing the AMD from the two Boliden mines, the ElectroClear AMD technology™ demonstrated, compared to lime treatment:

1. Low energy useThe ElectroClear AMD technology™ treated the AMD at mine #1 for as low as 7.5 kWh/1000L and 2.1 kWh/1000L at mine 2.

2. Water cleaning and metals removalThe ElectroClear AMD technology™ removed most metals at 95 to 100% and sulphate at 69% (mine 1). At mine 2, the technology again removed most metals at 95 to 100% and sulphate at 25%.

3. Reduced sludge generation and faster sludge settlingThe sludge from the ElectroClear AMD technology™ was one-seventh or 15% of the volume produced by lime treatment and settled 3 to 4 times faster than sludge from lime treatment.

4. Cost savingsThe costs are estimated at around 50% of lime treatment.

5. Improved sustainability performanceThe process avoids the need for lime, so avoids the carbon emissions and energy use involved in making lime. It also avoids the need for high volumes of water used in hydrating quicklime for the AMD treatment process and offers a pathway to use the metals and sulphates in the AMD. The ElectroClear AMD technology™ releases almost twice as much clean water compared to lime treatment.

Luke Berry, CEO
Ph +61 417 077 342
luke.berry@cleanandrecover.com.au
www.cleanandrecover.com.au

Introduction

Acid Mine Drainage (AMD) and other mine-influenced water has traditionally represented a significant management challenge to mining companies globally.  The United Nations (UN) has declared AMD the second biggest environmental challenge facing the world after climate change.

Clean&Recover has partnered with Boliden, a Nordic mining company based in Sweden, to demonstrate the techno-economic feasibility of using ElectroClear™ AMD treatment technology to deal with AMD at its closed and open mine sites.  The patented ElectroClear™ AMD technology uses electrodialysis to remove sulphates from AMD. ElectroClear™ AMD technology precipitates metals from the drainage for commercialisation and cleans AMD water so that it can be used on-site or discharged to the environment.  The key to the process is that it uses electricity rather than alkaline chemicals (such as lime or caustic soda) to neutralise the acidity in AMD and it processes the drainage with reduced residues and at lower cost to mine operators.

Boliden currently uses traditional lime treatment of AMD and other mine-influenced water to treat AMD. Boliden’s goal in partnering with Clean&Recover is to lower the operational cost of water treatment and return more and cleaner water to the environment compared to current AMD treatments. Other goals include reducing carbon dioxide (CO₂) emissions generated from water treatment, reducing power costs, and improving sustainability performance.

ElectroClear™ AMD technology has demonstrated that it can clean AMD to a standard suitable for environmental discharge while delivering on the UN’s Sustainable Development Goals.  More information about the ElectroClear™ AMD technology is available in Appendix 1 of this case study.

About Boliden

Founded in 1924, Boliden has more than 6,000 employees and has annual revenues of approximately SEK 85 billion ($US 8.3 billion/$AUD12.4 billion). Its shares are listed in the Large Cap segment of the NASDAQ OMX Stockholm. The company owns smelters, open pits and underground mines that produce zinc, copper, nickel, and lead for the European market. It also operates in the exploration and recycling markets, seeing the value of old deposits and waste.

Boliden’s vision is to be ‘the most climate-friendly and respected metal provider in the world.’ Guided by its values of Care, Courage, and Responsibility, it is Europe’s premier producer of sustainable metals.

Clean&Recover and Boliden partnered to test the ElectroClear™ AMD technology on the AMD impacted water at Boliden’s site. Clean&Recover built and installed a pilot plant in Sweden in Q2 of 2024 to demonstrate its performance in terms of energy use, treated water quality, reliability, and operational costs compared to lime treatment.  This case study presents the results of that work.

ElectroClear™ AMD technology: Small-footprint site pilot plant

Site pilot plant installed in Boliden (May 2024).

In Q2 of 2024, Clean&Recover worked with Boliden’s local staff to demonstrate the plant on two types of AMD, from AMD #1 (8 demonstrations) and AMD #2 (3 demonstrations). Data on energy use, treated water quality, amount of sludge generated, and rate of settling of the sludge were collected.

ElectroClear™ AMD technology results

In processing the AMD from the two Boliden sites, the ElectroClear™ AMD technology was demonstrated, compared to lime treatment across:

1. Energy use
2. Water cleaning and metal removal
3. Reduced sludge generation and faster sludge settling
4. Cost

In addition, the general sustainability performance of the ElectroClear™ AMD technology is set out under heading 5 below.

1. Energy use

The energy use savings varied due to the different water chemistries in the AMD processed from AMD #1 and AMD #2. AMD #1 has more dissolved metals and sulphate than AMD #2 which affected energy use.

AMD #1 used as little as 7.5 kWh/1000L, while AMD #2 used as little as 2.1 kWh / 1000L in the 11 tests for the two types of AMD.

2. Water cleaning and metal removal

The average percentage of metals removed over eight demonstrations for AMD #1 showed that ElectroClear™ AMD technology removed a very high percentage (between 90% and 100%) of most metals present in the AMD from AMD #1.

Significantly, this included removal of 100% of uranium (U) and over 69% of sulphate (SO4).  The resulting water was suitable for discharge into the environment under local laws.

The average percentage of metals removed over three demonstrations at AMD #2 also showed the removal of a very high percentage of contaminants, including close to 100% uranium (U). Again, the resulting water was suitable for discharge to the environment under local laws.

3. Reduced Sludge Generation and Faster Sludge Settling

Sludge generation was significantly reduced in samples treated with ElectroClear™ AMD technology (averaging 1 g/L) compared to conventional lime treatment, which generated averages of 7 g/L of sludge.  When considering the millions of litres of water treated daily at all of Boliden’s sites, the lower sludge volume from ElectroClear™ AMD technology treatment over time, will deliver significant savings in sludge handling.

Sludge from ElectroClear™ process	Sludge from lime treatment
1 g/L	7 g/L

Furthermore, the sludge produced from ElectroClear™ AMD technology settled much more quickly than the lime treatment sludge, leading to a much lower water holding cost.  The ElectroClear™-treated sludge settled between three and four times faster than the lime-treated sludge. The benefit is increased throughput without processes clogging, etc.

4. Cost 

The direct operating cost from using the ElectroClear™ AMD technology is low, consisting mainly of the per kWh charge associated with treating the water. A comparison with the local cost of lime treatment is being undertaken with Boliden’s mines.

Savings compared to lime can come from lower chemical costs, lower sludge handling costs, less clogging from gypsum from lime treatment, and lower labour costs.

5. General sustainability performance

The ElectroClear™ AMD technology promises a sustainable AMD solution without the carbon emissions associated with the use of lime. Lime generates carbon emissions because the process of making lime from limestone involves calcinating (roasting) the limestone, which drives off CO2 as a byproduct (CaCO₃ à CaO and CO₂). In addition, the calcination process is often powered by fossil fuels, which generate additional carbon emissions.

To illustrate the size of the potential savings in carbon dioxide emissions, a small flow of acid mine drainage treated with ElectroClear™ AMD technology could prevent the release of 3,000-4,000 tonnes of carbon dioxide every year compared to lime treatment.

The ElectroClear™ AMD technology is suitable to be powered by solar power.  Power interruptions do not damage the equipment, unlike other water treatment processes such as reverse osmosis. This further reduces the carbon footprint of the technology.

Additionally, the lime product made from roasting limestone must be hydrated, requiring high volumes of clean fresh water as input.

The ElectroClear™ AMD technology process produces water of suitable quality for either reuse on site, agricultural use, or for discharge to the environment.  If the water is reused on the mine site, it can be delivered at the preferred pH of the mine site, including up to pH 12 depending on the case.

In addition to this, ElectroClear™ AMD technology allows for the capture of valuable resources such as metals, water, sulphuric acid, and hydrogen gas from AMD waste.  These resources are otherwise trapped in the lime treatment sludge and cannot be used.

Environmental benefits using ElectroClear™ AMD technology compared with lime – general case

Environmental Benefit	Typical Impact per year
Carbon emissions avoided by not roasting limestone to make lime	3,600 tonnes per year of CO2
Energy saved by not making lime	181-634 MWh/year
Water saved by not hydrating lime	19 ML
Captured metals	378 tonnes
Additional water release from ECR AMD treatment	276 ML
Hydrogen gas from ECR AMD technology treatment	166 tonnes

Notes: At 95% water release from ECR AMD treatment compared to 50% from lime treatment.  Hydrogen production at 0.27g/L of AMD treated.  Energy use to make a tonne of lime is 40-140kWh: IPCC.

Contact

Luke Berry
CEO
Ph +61 417 077 342
luke.berry@cleanandrecover.com.au
www.cleanandrecover.com.au

Appendix 1

About ElectroClear™ AMD technology

The Challenge of AMD and other Mine-Influenced Water

Mining companies, including Boliden, face significant challenges in managing and treating AMD and other mine-influenced water. The level of contaminants in AMD far exceeds safe standards for discharge according to world and domestic water quality guidelines. AMD commonly has highly toxic contaminants such as mercury, arsenic, cadmium, cobalt, lead, and uranium.

Current AMD treatment methods include the use of lime or caustic soda to remove contaminants.  These methods of treatment are costly and operationally difficult, leaving large volumes of sludge that have the potential to clog pipework and contaminate sites beyond mine closure.

Treatments with lime and caustic soda face the following challenges:

• Adding lime or caustic soda to AMD generates large volumes of sludge.  The sludge carries significant water. The AMD lime treatment plant at Mt Morgan in Queensland Australia only returns 52% water from its processes, with the remainder of the water trapped in the sludge or lost as part of the process, compared with over 95% water return for the ElectroClear™ AMD technology.
• Lime or caustic soda treatments lock the metals present in AMD into the sludge, making them unrecoverable.
• Lime or caustic soda present risks to human health and safety during transport, storage, and handling.
• Buying and transporting lime or caustic soda to remote mine sites is costly.
• Adding lime or caustic soda to AMD has operational challenges, such as constant clogging of pipework through sludge due to poor solubility of lime and lower treated water cleanliness. This is compounded by the fact that the purity of lime is variable, making it difficult to determine how much lime to add to AMD to neutralise the AMD.
• Making hydrated lime from quick lime to add to AMD uses high volumes of fresh water.
• Making lime to treat AMD generates high volumes of CO₂.

Moreover, mining companies such as Boliden realise that AMD represents not just a waste and a remediation issue during mining but also an even longer-term environmental cost.  Boliden believes that AMD contains valuable elements that can be potentially reused to offset the costs of rehabilitating and treating the mine water ahead.

ElectroClear™ AMD technology

Erik Ronne, Boliden’s Research Manager – Sustainability, says:

Initial tests at Clean&Recover’s plant in Queensland with highly contaminated acidic water from our [AMD # 1] were indeed very encouraging with low operational cost per cubic meter and high purification efficiency. However, from our perspective ElectroClear’s™ Zero CO₂ emissions is also an important driver, since traditional treatment of acidic mine water includes lime treatment, which releases huge amounts of CO₂. We are indeed happy to further evaluate this technology in collaboration with Clean&Recover.

Achieving the UN Sustainable Development Goals

ElectroClear™ AMD technology helps to achieve the following UN Sustainable Development Goals (SDGs):

UN Sustainable Development Goal	ElectroClear™ AMD technology
SDG 6.3 – Clean water and sanitation – improve water quality by reducing pollution, halving the proportion of untreated wastewater, and substantially increasing recycling and safe reuse globally.	ElectroClear™ cleans AMD produced by mining, which is otherwise impounded in huge tailings dams or discharged into waterways. ElectroClear™ cleans the water to a standard acceptable for discharge to the environment.
SDG 12.4 – Ensure sustainable consumption and production patterns – achieve the environmentally sound management of chemicals and all wastes through their life cycle.	ElectroClear™ eliminates the use of chemicals in the treatment of AMD and greatly reduces toxic sludge that is traditionally produced by adding chemicals to AMD.
SDG 12.5 – Ensure sustainable consumption and production patterns; Substantially reduce waste generation through prevention, reduction, recycling, and reuse.	ElectroClear™ turns a waste product (AMD) into a valuable resource (metals, clean water, sulfuric acid, and hydrogen gas).

Mines face significant challenges managing and treating AMD, including removing contaminants at levels far in excess of safe standards for discharge according to world water quality guidelines.

Many mining companies are dealing with a number of closed or soon-to-be closed mines around the world with significant flows of mine-influenced water.

These mines are looking for short-term solutions to remove contaminants.  But current methods of treatment come with multiple costs and operating issues without any value-adding options.  The current process of active treatment using lime or caustic soda presents the following challenges:

• The sludges trap significant water.  For example, an analysis of a lime treatment plant at Mt Morgan found that it only generates 52% water return from its operations, with the remainder of the water trapped in the sludge or lost as part of the process.
• These methods involve the addition of large volumes of lime or caustic soda, which can pose environmental risks if added at rates in excess of requirements.
• These forms of treatment lock the metals present in the AMD into the sludge, making them unrecoverable.
• The lime or caustic soda are safety risks during transport, storage, and handling.
• Adding the lime or caustic soda to AMD has lots of challenges such as the poor solubility of lime, armouring, and poor purity.
• Transporting lime or caustic soda to remote mine sites is costly.

Moreover, mining companies are coming to see that acid mine drainage represents not just a waste and a cost.  It contains potentially valuable elements that can be used to offset the costs of rehabilitating and treating the water to return it to a useable state.