Turning acid mine drainage into drinking water

29th August 2008

Acid mine drainage water is a major threat to the environment, but it also constitutes a major resource for the production of high-quality drinking water through the process of precipitation and desalination.

South African turnkey project house Keyplan has developed a high-recovery precipitation reverse-osmosis (HiPRO) process for the treatment of acid mine drainage.

A world first, this high-tech process transforms water with a high acidity and sulphate concentration into superior-quality drinking water for use by local communities.

After several successful pilot programmes at Anglo Coal’s Landau colliery demonstrating the process, Keyplan was invited to tender for the Emalahleni water reclamation project, in Witbank.

Based on this innovative process, Keyplan was awarded the turnkey contract by Anglo Coal to design, construct and commis- sion a 200-million-litres-a-day plant to treat acidic, saline mine water originating in the Witbank coal-mining region to a high-quality potable water standard.

The water originating at Anglo Coal’s Greenside, Kleinkopje and Landau collieries, and BHP Billiton Energy Coal South Africa’s (Becsa’s) now redundant South Witbank colliery is treated in the plant and then supplied directly to the Emalahleni local municipality potable water reser- voirs.

The engineering phase of this R300-million project began in late 2005 and construction was completed in 2007. Since commissioning, the plant has consistently produced high-quality potable water ranging between 18-million litres and 24-million litres a day at 99% recovery.

Shortly after commissioning the Emalahleni water reclamation plant, at Witbank, a contract based on the same technology was awarded to Keyplan by Becsa.

The plant will be installed at the Optimum colliery to treat coal mine drainage water arising from the mining process.

Not only does the process treat the wastewater, but it also produces high-quality potable water, which will allow the Optimum colliery and the nearby town of Hendrina, which is currently experiencing a water shortage, to be self-sufficient.

Excess treated water will be pumped and discharged into the public stream, further improving water quality in the catchment area. The water reclamation plant will cost over R200-million and be capable of treating an excess of 15-million litres a day.

Construction of the terrace has begun and completion of the reclamation plant is expected by the middle of 2010.

The process uses multistages of ultrafilitration and reverse osmosis (RO) membrane systems operating in series and with interstage precipitation of low solubility salts. The heart of the process is the RO desalination units which produce supersaturated brine from which sparingly soluble salts may be precipitated.

The Keyplan HiPRO pro- cess has been developed in South Africa where it is expected to revolutionise the treatment of acid mine water effluent discharges, while at the same time producing drinking water for the local communities.

With interest in the process evident from local and overseas sources, the process has the potential not only to benefit the environment and communities, but also to enhance the management of scarce water resources by supplementing diminishing supplies to meet the everincreasing demand.