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AMD technology a hot topic in South Africa

ENVIRONMENTAL IMPACT Acid mine drainage, which has a high sodium content, has a negative effect on agricultural land when it is discharged into rivers that are used for irrigation

Photo by Duane Daws

LASSE MUSAKKA South Africa has been selected as the primary market for Global EcoProcess Services’ mine water treatment technology after extensive market studies

Photo by Duane Daws

JOHN BEWSEY Trailblazer Technologies’ key focus is the supply of sodium-free water at affordable levels for agriculture

Photo by Duane Daws

26th August 2016

By: Robyn Wilkinson

Features Reporter

  

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Finnish specialist in hydrometallurgical treatment technology Global EcoProcess Services (EPSE) launched a treatment for acid mine drainage (AMD) in South Africa in July, which it claims is a cost-effective, one-step process that can integrate with the existing technology and equipment used by mines to treat hazardous wastewater.

EPSE’s technology treats wastewater containing soluble metals, sulphates and hazardous brine-forming elements, such as sodium, by rendering the precipitated metals in the water irreversibly insoluble and environmentally harmless, explains EPSE South Africa country manager Gregory Niekerk.

“EPSE’s technology for the extraction of metals from mining and industrial effluent waste streams essentially turns hazardous waste into valuable raw material for various applications. After extensive global market studies, South Africa has been selected as the primary market for the expansion of this mine water and industrial hazardous waste treatment technology,” says EPSE CEO Lasse Musakka.

After extensive testing in Europe, EPSE states that it is ready to introduce its system to South Africa, stressing that it does not seek to establish itself as an operating company in South Africa’s waste management sector but rather to offer the solution as an additional component to enhance existing treatment processes and equipment. EPSE is, thus, seeking to partner with interested technology providers to perform pilot tests in the country.

The large pools of acidic water produced by mining operations are harmful to the environment, owing to the sulphates, iron, toxins and heavy metals they often contain, highlights University of the Witwatersrand Industrial and Mining Water Research Unit codirector Dr Kevin Harding. While there are several treatment options available to manage AMD, he notes that these are typically expensive or only moderately effective and, historically, mines have, thus, shown a reluctance to take responsibility for the treatment of their process water.

Globally, declining ore grades require more water to be processed, adds EPSE director of international relations Felix Fondem, noting that this leads to an increase in the amount of AMD that is produced. Consequently, he says, there is an increased emphasis internationally on water recycling and environmental protection.

As a water-scarce country that has experienced drought conditions in many provinces this year, the company stresses that South Africa needs to prioritise cost-effective treatment options for AMD that can both protect the environment and increase the recyclability of water in the country.

EPSE’s solution provides a novel treatment for AMD that Musakka describes as “simple, fast, scalable and cost efficient”. EPSE partner Vesa Kainulainen explains that a combination of boric compound and alkaline is added to the mine water in a single-step process. What results is recovered water that can be reused in mining processes or rendered potable through sulphate removal technologies. Vesa states that a number of joint patents with existing customers are pending for new and unique products generated from their waste.

Musakka highlights that the solution produces an irreversibly insoluble and inert precipitate. This is important as soluble precipitates of heavy metals are classified as hazardous waste that must be stored in controlled landfill deposits, creating an indefinite environmental risk and long-term postclosure liabilities on the balance sheets of mining, industrial and waste treatment companies.

EPSE’s solution, which is effective with both a low and high level of metal concentration, can be newly built or used to retrofit to existing treatment plants at marginal capital cost and with limited, if any, operational disruption during the construction phase, says Niekerk.

“Our technology has been tested and verified by independent accredited laboratories and has been put through industrial pilot tests, and is estimated to be able to achieve potential yearly savings of up to €1-million, according to conservative calculations made at an operational mine with AMD problems in Finland,” Musakka adds.

EPSE is confirming these cost gains at both large and medium-sized mines in South Africa, with Niekerk noting that early indications of the company’s work in South Africa suggest that EPSE’s solution can be installed at one-tenth of the capital intensity and less than half the operating cost of currently operating plants.

He notes that the company’s collaboration with local entities extends from testing AMD generated in both gold and coal mining as well as highly concentrated multimetal effluents from industry and the inductotherm welding and heating technology sector to designing a further simplification of its offering with local original-equipment manufacturers and engineering houses and working with other technology providers and national research and development centres to integrate EPSE’s method with other treatment technologies.

“With our partners in South Africa, we will be able to release auditable results in the next six to twelve months, confirming that an integrated EPSE solution produces a permanent solution for the worldwide environmental problems created since the dawn of the industrial revolution,” concludes Niekerk.

Local Alternative
At the South African launch of EPSE’s solution for AMD treatment, Department of Water Affairs and Sanitation (DWS) assistant director Bashan Govender noted that the South African government has investigated possible solutions to the management of AMD through various projects. While these have had some degree of success, he claimed that the funding needed to further these projects was difficult to obtain as AMD treatment was unprofitable.

However, in May, Mining Weekly reported that Krugersdorp-based company Trailblazer Technologies had produced a profitable treatment solution, known as the KNeW process. KNeW is able to convert AMD into valuable fertiliser materials that can be sold for a “handsome” profit, while simultaneously producing usable water at no cost.

“With the KNeW process, the dissolved solids in AMD are converted into fertilisers, leaving clean usable water. The sale of the fertilisers offsets the cost of the treatment process, therefore, the water can be supplied at an affordable price. In other words, the process does not rely on having to sell its product water at domestic prices to try to offset the cost attributed to the process. A further advantage is that the fertilisers produced are able to replace important nutrients in the soil,” says Trailblazer Technologies director John Bewsey.

Through the KNeW process, the acidity in AMD is neutralised with soda ash. The large gypsum precipitate that is usually produced using other methods is, thus, avoided and the minor quantities of heavy-metal pollutants can be removed as a concentrate and rendered immobile as they are fixed in a cement. This ensures that they are never again released into the environment. The effluent solution is then filtered and fed into an ion exchange plant, which removes the cations (mostly sodium) and the anions (sulphates and chlorides). The sodium nitrate solution is then converted in a double decomposition reaction into sodium chloride and potassium nitrate, which are further processed and sold to the industrial and hydroponics markets.

In the past few months, Chinese producers have dumped potassium nitrate on the market at a price of $870/t. However, Bewsey highlights that it is generally a very stable commodity that traded at a world price of $950/t for a decade before. “We expect that the price will soon return to stability when these producers have exhausted their excess stock,” he says.

Bewsey outlines that, using this solution, a typical plant processing 15-million litres of AMD a day will, thus, generate R250-million a year in sales. “If we build three plants, which South Africa easily requires, we could process 45-milllion litres a day, or 5 500-million litres a year, and generate import replacement sales of R750-million a year. Because of the potential for profit from the process, the cost of producing water would, in fact, be negative. Obviously, no business is going to do this, so, realistically, the water would be supplied at no more than a few cents for every cubic metre.”

He points out that South African farmers, extracting water from a waterway, pay 33c/m3, while domestic users pay between R7/m3 and R15/m3, and industry and mining about R10/m3.

“Our key focus is the supply of sodium-free water at affordable levels for agriculture . . . If we want food security in the future, our recovered water must be returned to the rivers at prices that can support food production [while preserving] our arable lands,” says Bewsey.

He emphasises the importance of water used for agricultural irrigation being sodium free as sodium is extremely damaging to agriculture. It attaches to clay particles in the soil and renders it impervious to water penetration and oxygen ingress, which is necessary to support the vital organic life in the soil. Total mine drainage discharge (including coal mines) averages about 350 000 ∙/d, with an average sodium content of about 900 parts per million, and this is all discharged into the river system, which is used primarily for agricultural irrigation. Bewsey points out that this introduces about 60 000 t/y of sodium to South Africa’s limited arable soils. Moreover, he highlights that coal mines are, in terms of their sodium pollution, collectively a lot worse than the gold and platinum mines, owing to the saline leaching from the overburden above the coal seams – a fact which is generally ignored when dealing with AMD processing.

“As over 60% of South Africa’s water is used by agriculture, it is important for treatment processes to be able to deliver sodium-free water at almost no cost. Until the development of the KNeW process, this had never before been achieved.”

Trailblazer Technologies is in talks with potential investors and expects its first treatment plant to come on line in 2018 in the Northern Cape. Despite various attempts, the company has not been granted an audience with the DWS to discuss its AMD solution.

Meanwhile, in May, Mining Weekly reported that Water and Sanitation Minister Nomvula Mokonyane had launched a long-term AMD project in the Western, Central and Eastern basins of the Witwatersrand goldfields. The first phase of the project cost of R2.3-billion, with a further R10-billion investment planned for the implementation of either reverse osmosis or desalination technology to further treat AMD.

Edited by Tracy Hancock
Creamer Media Contributing Editor

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