12 WATER MANAGEMENT From Toxic to Tap: Mine-Water Becomes a Commodity

A historic project to convert polluted mine-water into quality drinking water is moving ahead in Emalahleni (Witbank), Mpumalanga. The R300-million joint initiative between Anglo Coal and Ingwe Collieries will see the treatment of 20 Mℓ/day of acid mine drainage (AMD) from three collieries for sale to the Emalahleni Local Municipality. Lani Holtzhausen reports.

hen travelling through the potential safety risk. Where mining poort catchments, which are situated Highveld in Mpumalanga, activities have ceased, the under- downstream of the Upper Olifants Wthere is no doubt why ground workings are filling with water. catchment, it has been recognised South Africa is the third-biggest coal that the water that is available producer in the world. Mine after Collieries exploiting the Northern Wit- requires crucial management. mine tells of the legacy of this area, bank Coalfields have to continuously in which up to 90% of the country’s pump out this water to reach the coal A NEW APPROACH saleable coal is mined. seams. According to South African environmental law, this water has to A few years ago, having exhausted all However, more than a century of be suitable for release back into the other water management options An- open-cast and underground mining environment, and may need to be glo Coal and Ingwe Collieries agreed has impacted on the surrounding en- managed and treated before being to cooperate to find a long-term solu- vironment. Coal mining has a signifi- released so as to reduce pollution of tion. The result of years of research cant effect on the hydrological cycle, the country’s scarce water resources. and development is the Emalahleni with surface water working its way This has become even more impor- Water Reclamation Project which, into underground voids and becom- tant in the Upper Olifants catchment, for the first time in South Africa, will ing polluted as it comes into contact where many of these mines are see the abstraction and treatment with exposed sulphur-bearing pyrite. situated, as the area suffers from a of mine-water from existing and old chronic shortage of water. mines to a level that is fit for use by It is reported that the accumulation the local municipality. It is anticipated of water in active mines has already With future mining developments that water will be treated from Anglo increased to the extent that it ham- earmarked for the short to medium Coal’s Kleinkopje and Greenside pers mining activities and poses a term in the Middle Olifants and Steel- collieries, as well as Ingwe’s South

The Water Wheel May/June 2006 WATER MANAGEMENT 13 From Toxic to Tap: Mine-Water Becomes a Commodity

Witbank Colliery, a defunct operation on the other hand, will already be of Above: The construction site of the where mining stopped in 1969. good drinking water quality.” first 20 Mℓ/day mine-water to tap water reclamation plant being While the sale of the water will allow the Anglo Coal senior project manager constructed outside Emalahleni mining companies to offset some of Peter Gunther reports that the (Witbank), Mpumalanga at present. the costs of treating the water, it seems municipality requires an additional this project has come just at the right 20 Mℓ/day of water which the mining THE TREATMENT time for the Emalahleni Local Munici- companies can easily provide with PROCESS pality. According to Emalahleni head this project. “Studies have shown that of department: water services Lindela the mined out voids in the area could Most mines in this catchment area Tshwete the municipality, which is the hold more water than the Witbank have a water quality associated with water services authority for the Witbank Dam, resulting in the mines being a calcium-magnesium-sulphate. This area is already exceeding its allocated huge potential source of water makes the water more treatable than amount of water from the Witbank Dam, supply,” he told other mine-water high in sodium its sole bulk water resource, drawing the Water chloride (a typically some 80 to 90 Mℓ/day at present. Wheel. characteristic of AMD from Tshwete reports that the municipality gold mines, has decided to buy into the Emalahle- for example), ni Reclamation Project rather than the as more Vaal River Eastern Sub-System Aug- mentation Project (VRESAP), which is also being constructed at present, for a number of reasons. “Buying bulk water from the VRESAP pipeline would have cost about twice as much as water from the mines. In addition, we would have received raw water from the pipeline, which would then first have to be treated. The water received from the reclamation project, Flows of 120 m3/day were achieved at the demonstration plant.

The Water Wheel May/June 2006 14 WATER MANAGEMENT

treatment proc- esses can be used Kleinkopje to desalinate the Treatment Colliery Mine-water Potable water waters. plant storage storage Following the evalu- ation of a number Emalahleni of possible water Greenside Town treatment technolo- Colliery reservoirs gies, Johannesburg firm Keyplan’s de- sign was selected. A 120 m3/day de- South Witbank monstration plant Colliery was established at Landau Colliery to Sludge/brine prove the efficacy of disposal the technology over a trial period of three months. One of the Main components of the Emalahleni Mine-water Reclamation Project. most important criteria was to achieve a high yield. allowing metals such as iron, alumini- exposed of in evaporation ponds with “We were initially aiming for a yield um and manganese to precipitate out. a capacity of 330 000 m3. All neces- of 95%, but actually succeeded in sary regulatory steps have been achieving a yield of 98% during our Following clarification, the water will followed to establish these hazardous trials,” reports Gunther. This not only be treated using ultrafiltration (UF) to ponds which will be double plastic- increases the output from the plant, remove any remaining metals. This lined to eliminate any seepage. but minimises the volume of waste that process will also remove any bacteria has to be dealt with. that might be in the water. About 500 An on-site laboratory will provide analy- UF membranes will be installed. This ses of the water for process purposes Following approval in September, will be followed by reverse osmosis that will also be used to check for some construction of the main plant started using spiral membranes to remove re- basic parameters of the potable water in November last year. Water will maining salinity. Just under 1 200 RO before it is pumped to the municipality. be collected at the membranes will be used. The mem- three mines and brane treatment process is repeated conveyed via three times to ensure maximum yield three separate and maximum brine concentration. pipelines to two Two identical process trains are storage facilities being established, each capable of at the treatment producing a minimum of 14 Mℓ/day. site. To cater for seasonal fluc- The treated water will be stored in two tuations the two 10 Mℓ/day dome-shaped concrete storage dams reservoirs before being pumped to will have a com- an Emalahleni municipal reservoir bined capacity about 9 km away for distribution to of 46 Mℓ. The consumers. To ensure an uninter- acidic water will rupted supply all critical mechanical firstly undergo and electrical components required a neutralisation to keep the plant at full capacity must process using have an installed standby. CSIR’s lime/lime- stone treatment The process will produce about The CSIR lime/limestone process is 3 process. This in- 100 m /day of brine and 100 t/day of used to increase the pH of the water creases the pH gypsiferous waste. The brine will be prior to ultrafiltration. WATER MANAGEMENT 15

Results from the demonstration plant indicated that the pH levels of the water was boosted from 2,9 to be- tween 6,5 and 7,5. The total dissolved solids count was reduced from as high as 4 500 mg/ℓ to 135 mg/ℓ while the sulphate content was reduced from 3 500 mg/ℓ to 80 mg/ℓ. The treated water is within the SABS 241 Class 0 drinking water quality limit.

FIRST FOR SOUTH AFRICA

It has been a long and interesting journey for the two mining companies After the pre-treatment process the water is clarified before being sent through since the signing of their cooperation the ultrafiltration membranes. agreement. Ingwe project engineer Wendy Mey says the fact that two competing mining companies have cooperated to find a solution that will not only benefit the environment, but also surrounding communities, is a milestone in itself.

At the time of writing the reclamation plant was 20% complete. It is hoped to complete construction before the end of 2006, with commissioning starting in early 2007. By the third quarter of that year, the plant should be fully operational.

Meanwhile negotiations are being Spiral reverse osmosis (RO) membranes are used to remove salinity in the finalised with the Emalahleni Local water. Up to 500 RO membranes will be installed on the main plant. Municipality, with the final I’s being dotted and T’s being crossed on the which people can comment on the management issues are being experi- water supply contract. Gunther notes project, and where queries can be enced. Mey notes, however, that it will that throughout the project regular answered, has been suggested to not merely be a case of replicating consultation has ensured that the allay any future concerns. the technology. The area faces differ- local authority’s interests have been ent challenges, for example, there are recognised. Tshwete confirms that Getting all the regulatory require- more open-cast mines, and the water the municipality has been part of ments in place has been quite a will have to be piped further. Studies the process from the start, and has challenge. A water supply licence are ongoing to find the best solution praised the mining companies’ ef- has never been issued for treated for this area. forts in establishing a good relation- mine-water in South Africa before, ship with its prospective client. for example. According to Gunther, It is anticipated that a regional water all the relevant authorities have been supply company may eventually be In addition, a series of community represented on the project steering established to manage the distribu- meetings have been held to appease committee to ensure the process tion of the water treated by the water any fears the people of Emalahleni goes as smoothly as possible. reclamation projects. It is hoped that might have with regard to drinking these projects, as well as similar treated mine-water. Tshwete says A similar project is now in the pipeline future initiatives, will provide a long- communities have been well in- for the Steve Tshwete (Middelburg) term solution to South Africa’s mine- formed, and a regular newsletter, in area, where similar mine-water water problems.

The Water Wheel May/June 2006