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Fraser Alexander, Miwatek launch new AMD treatment technology

11th June 2008

By: Idéle Esterhuizen

  

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JOHANNESBURG (miningweekly.com) - Mining solutions company Fraser Alexander and water treatment company Mine Water Treatment Technologies (Miwatek) on Tuesday launched their acid mine drainage (AMD) treatment solution, in Randfontein, west of Johannesburg.

Unlike traditional AMD treatment solutions, which generate high volumes of sludge and brine, the Miwatek technology offers a total solution and allows for the production of reusable waste, which cofounder Pieter Jansen said rendered it more cost-effective than other technologies.

It is also the only water-treatment solution that offers the benefit of about 50% less solids (waste) compared with the industry average, he added.

The solution incorporates sophisticated modelling, based on the chemical analysis of the specific water to be treated, the locally developed Abrimix Mixer technology and reverse osmosis (RO) membranes from US-based stakeholder Jalema Technologies, which enables optimal plant design and, therefore, an optimal water treatment solution.

Typically there are two or three stages of RO recovery, with chemical pretreatment stages before each RO stage.

The Miwatek solution can also integrate a type of evaporation and crystallisation technology into an overall process proposal that can deliver zero liquid discharge with all of the crystal products in the form of industrial quality reagents, rather than a mixed crystal mass that has to be disposed of.

Chemical and waste expert and consultant Dr Richard Paxton pointed out that, as the technology offered the benefit of analysis-based design, it could be adjusted according to the requirements of each client to ensure an optimum AMD treatment solution.

Fraser Alexander water treatment division head Ken Bouch said the firm had taken the decision last year to buy a stake in Miwatek and commercialise the technology, which it saw as complementing its existing services.

“The process is flexible, innovative, comprehensive and solves one of the main challenges of AMD treatment, which is the large volume of hazardous waste, while allowing for high recovery of discharge-compliant water,” he indicated.

The technology also offers the benefit of treating variable feed-water qualities and significantly reducing life-cycle costs, as the long-term liabilities that were associated with the disposal of the residues would be significantly lower.

Bouch further stated that the Miwatek plants would not be sold to clients, but that they would be designed and built by Miwatek, but owned and operated by Fraser Alexander during and beyond the life of the mine.

“Effectively, clients would only pay for clean water, which means no process risk for the client,” he noted, while adding that the Miwatek role-players also sought to keep the intellectual property behind the technology in-house and would, therefore, only offer an on-sight water treatment service, rather than selling the plants.

Bouch said Miwatek partner Steval Engineering constructed a pilot plant at gold miner Gold One’s Number 8 shaft, last year, which had proven to be successful, adding that this had served as motivation to launch the technology. He said mining firms had already expressed significant interest in the technology and that a two-week-long promotional period was currently under way to demonstrate the solution to potential clients.

The pilot plant, which boasted a capacity of 12 m3/h and which is only a two-stage RO plant, is capable of achieving a minimum of 98% water recovery rate.

Further, Jansen said the Miwatek solution also offered faster calcium control and membrane protection. “Mixing reagents to fix the gypsum problem used to take three to four hours but, with the new technology, this is reduced to minutes, which results in a significantly reduced plant footprint.”

“This process has taken us a major step forward, with it being analysis driven, the Abrimix unit and the reusable waste products,” Miwatek cofounder and Jalema Technologies owner John Lombardi told Mining Weekly Online.

He stated that mining firms would appreciate the convenience offered by the Miwatek solution. “No mine manager is trained in water treatment at university, so they are happy to sign a cheque and let somebody else do it,” Lombardi noted.

Meanwhile, Miwatek was also in the process of piloting a solution that created a relatively diluted and low-quality caustic soda solution from the final brine, which should be sufficient to replace much of the hydroxide input that is needed for all of the pretreatment reactors.

This process addition, where feasible, would enable overall brine production to be at least halved and, in some instances, almost eliminated; the third pretreatment and RO stage to be avoided and high-purity gypsum to be created.

Edited by Chanel de Bruyn
Creamer Media Senior Deputy Editor Online

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