South African petrochemicals giant Sasol is forced to take drastic measures when it comes to its environmental protection efforts, especially at its Secunda-based underground coal mining complex, which covers more than 1 100 km2 and is one of the largest in the country, says Sasol spokesperson Alex Anderson.

Sasol Mining supplies about 40-million tons of coal to synthetic fuels plant Sasol Synfuels, in Secunda, and two- million tons of coal to Infrachem, in Sasolburg, every year.

While Sasol also exports coal to European and Asian markets, its main operations comprise the Bosjesspruit, Brandspruit, Middelbult, Syferfontein and Twistdraai Export operations, in Secunda, and the Sigma-Mooikraal operation, near Sasolburg.

Dust Control

Anderson notes that, because coal mining has become “highly mechanised” and more technology is used in these extraction methods than in other methods, it is also more sophisticated than other types of mining.

He adds that Sasol Mining has been incorporating dust-suppression interventions and technology since the 1960s and has been at the forefront of developing new dust-suppression equipment and techniques in South Africa.

“Mining technology has become increasingly sophisticated. We have continuously explored and tested these innovations through research and development, and have incorporated them into our operations to enhance the safety and health of our employees.”

Sasol’s continuous miners (CMs) are remote- controlled and contain dust-suppression technology, such as high-pressure water-spray systems and scrubbers, which are installed on all of the miner’s dust-suppressing CMs.

Sasol also undertakes daily dust-suppression inspection and reports to the Department of Mineral Resources on the company’s dust levels as part of its policy to continuously monitor all operations.

Further, the company notes that all Sasol Mining employees are equipped with the appropriate personal protection equipment, including gumboots, overalls, eye protection, ear protection, hard hats, gloves, dust masks, and self-rescue packs, which comprise emergency oxygen devices.

“With extensive underground mines in Secunda and at the Sigma colliery, in Sasolburg, Sasol Mining has always ensured that its operations are properly ventilated,” says Anderson, adding that additional ventilation shafts are often installed in Sasol’s mines to improve ventilation supply.

“Providing ample ventilation for the mines, specifically the coal-winning areas, also contributes to a healthier working environment,” he notes, further stating that large quantities of clean air entering the mine areas underground dilute the dust concentration and remove dust from the environment.

Anderson adds that dust-suppression equipment and the treatment of roads with dust-allying products, such as surfactant chemicals sprayed onto the surface, as well as a good ventilation supply, assist companies in reducing dust particles in mines.

Approach to Water Management

Sasol’s approach to mine water management is based on a comprehensive strategy, aligned with best-practice guidelines for mine water management and developed by the South African Department of Water Affairs (DWA).

These guidelines identify benchmarked environmental practices and prescribe norms and standards that regulate water use and protection, based on a hierarchical approach to water management that aims to reduce water consumption and the generation of contaminated water at source. The approach also aims to increase water recycling and reuse, encourage water treatment to render the water usable and manage the storage and final disposal of mine water.

The hierarchical management approach involves the implementation of the best technology available to reduce water consumption and the impact of water consumption on the environment.

“All of Sasol Mining’s operations have been designed to operate as zero-liquid-effluent discharge systems,” says Anderson, adding that the primary strategy in implementing the hierarchical approach is to recycle and reuse as much water as possible.

This involves storing water underground and treating surplus water, which is brought above ground for upgrading in a mine water desalination facility at Sasol Synfuels’ coal-to- liquids processing facility in Secunda.

Managing Mine Water

Anderson says Sasol Mining is fortunate to operate in circumstances that naturally preclude the need to address acid mine drainage. The acidic nature of water typically arises from its exposure to the ore, which has sulphide minerals in a wet and oxygenated environment.

“At Sasol Mining’s Sasolburg and Secunda coalfields, the presence of carbonaceous rock effectively buffers the acid generation.”

This results in the water containing a neutral to alkaline pH, accompanied by elevated sulphate concentrations and an associated high total dissolved salt content and electrical conductivity, with the concentration of trace elements being well within a safe parameter.

From a storage, recycle and reuse perspective, the underlying principle is to keep underground mine water in the mined-out area, says Anderson. This is achieved by storing water in underground compartments to reduce spillages in the environment. On a monthly basis, these compartments are monitored to assess the volumes stored and the risk of compartment failure.

“In areas where mining is being conducted, Sasol pumps water to surface dams, where it is treated and reused underground for dust suppression, coal washing and machine cooling,” says Anderson.

Further, in accordance with guidelines stipulated in approved environmental management plans, any excess water is temporarily stored and fed into an electrodialysis reversal (EDR) water treatment plant before being used at Sasol’s synfuels plant.

The salty brine product from the EDR plant is treated in a mechanical evaporator and is then treated by a crystalliser to produce a range of salt products that are sold to external markets.

Water Management after Mine Closure

Anderson points out that the closure of a mine typically involves several environmental and water management challenges that need to be carefully monitored.

Sasol Mining has investigated the risk of future decant situations at its mines in Sasolburg and Secunda to quantify the potential environmental consequences associated with any contaminated mine water, particularly after a mine has closed.

“Various modelling studies have been undertaken, based on detailed geological information and an understanding of aquifer characteristics. The conclusions of these studies favour the storage of water in available underground compartments at our Sasolburg and Secunda operations.”

Anderson further explains that, in the event of mine closure, a natural rise in water levels will enable the mines to flood quickly, which will avoid any further reactions, owing to the presence of oxygen. The water levels will return to the premining levels, with observed stratification.

Community Upliftment

Sasol Mining is implementing a range of projects that contribute to the sustainable development of the communities in which it operates. In recent years, the company has invested R17.8-million as part of its social and labour plans.

Two footbridges, with an estimated collective value of R1-million, were constructed in Mpumalanga in 2010, the first of which now enables community members to safely access the local community clinic, as the bridge crosses a path that floods during rainy seasons. The second footbridge enables the community to safely cross the Welas river, thereby providing access to schools, clinics, shopping centres and local factories. Anderson tells Mining Weekly that 32 000 households will benefit from these footbridges.

Meanwhile, a R7-million clinic in Koppies, in the Free State, which is scheduled for completion in March, will provide primary healthcare services, maternity and dental care, tuberculosis and HIV/Aids treatment as well as emergency medical services.

Construction of the clinic is under way, which will include several consulting rooms, a pharmacy and a staff kitchen, and is set to benefit 20 000 households.

“Further, Sasol is solving sewage reticulation and supply issues by installing a new 20 000 ℓ supply tank; it is also paving, fencing and providing furniture for the new extensions,” says Anderson.

“Two sewage suction trucks were handed over to the Charl Cilliers settlement, in Mpumalanga, with each truck costing R1.5-million, which benefits around 500 households.”

Further, Sasol is investing about R8-million in the Leandra settlement fire station, in Mpumalanga, which is being upgraded to enable effective fire control. The investment will include a new fire truck, four light delivery vehicles and firefighting equipment. Construction started in August 2013 and is expected to be complete by the end of 2014.

Sasol has also upgraded the Emzinoni Clinic, in Bethal, Mpumalanga, beyond its initial project scope to ensure that the clinic can provide more healthcare services, such as dental care, overnight care and rooms for consultation and wound dressing, as well as social and support services, including administration rooms, waiting rooms and a dispensary. “Around 23 000 households will benefit from this project,” says Anderson.

“Infrastructure, including sewerage, water and power infrastructure, was upgraded, and an emergency water and oxygen supply area was added. Sasol Mining invested R11-million in this project, with an initial budget of R7.7-million,” says Anderson.

Sasol also completed a stormwater drainage system in the Lebohang township, where 38 households and a secondary school housing 1 500 learners benefited from the project. Construction was completed on April 30, 2012, at a cost of R1.2-million.

Moreover, the company invested R2.8-million to repair and seal the five-million-litre Kinross water reservoir, in Mpumalanga’s Govan Mbeki municipality, which was initially built and commissioned in 2009.

“Even though the reservoir was fairly new, it was leaking before it came into use and, if used, it could pose a danger to the community,” says Anderson.

As a result, Sasol undertook to study the reservoir structure and the causes of the leaks in February 2013.

“The company also invested R15-million in learnership training for mining-related skills development and allocates 25 bursaries a year to members of the local community in Mpumalanga,” concludes Anderson.