The current acid mine drainage (AMD) crisis in South Africa, coupled with the impending scarcity of natural resources in the country and the enforcement of environmental legislation, such as the National Environmental Management Act, is forcing industry stakeholders to take a closer look at the impact of their mining processes on the environment.

Local pumps manufacturer Verder Pumps consultant Daan Louw says mines are forced to seek out appropriate recycling and water treatment processes before reintroducing used water to the environment.

AMD in South Africa has reached the stage where damage is prevalent, especially in the Western, Central and Eastern basins, and a management programme is required to maintain water levels at below environmental critical levels.

Rand Uranium water treatment plant head Dr Basie van der Walt says the company started working on AMD management at the mine’s Randfontein operation in 2002, after the Western basin flooded and started decanting onto the surface in September that year. During that time, Rand Uranium was treating 12-million litres of acid water a day, says Van der Walt.

He adds that, while water is pumped from 65 m below the surface at the mine’s Number 8 shaft, last year’s summer rainfall compounded the situation, raising the water level to 41 m below surface, which caused flooding at 17 and 18 Winze shafts.

“The AMD is pumped into the Black Reef incline decant dam where it is pretreated with limestone to protect the pumps and pipes throughout the process,” says Van der Walt. “The water is then pumped 4.2 km to a treatment plant where most of the treatment procedures take place.

At the beginning of the process, before the water is treated, the pH level of the water is about three, but after treating the water by dosing it with limestone and lime, pH levels are about eight.

Part of the treatment process involves aerating the AMD to ensure it complies with the Department of Water Affairs’ specifications before it is pumped into the Crocodile river.

Louw points out that the mining companies have to achieve their operational goals while fixing the AMD problem and ensuring that a mining operations’ impact on the environment is minimal. Verder Pumps therefore aims to support its clients by providing pumping solutions, he says.

The company tries to source the most ideal solution for a particular application and, in the case of Rand Uranium, Verder Pumps identified two VF65 pumps and one VF40 pump as the most appropriate solution to deal with the pumping tasks.

Verder also believed training on the pumps would be necessary and facilitated a training programme for Rand Uranium staff at Verder’s premises in North Riding.

Peristaltic Pump
Louw further highlights the importance of identifying the nature of the material that needs to be pumped when selecting a pump for a specific application. Lime, for example, is a high-viscosity medium, which often causes pumps to clog up, resulting in maintenance problems.

Especially in cases of treating AMD, a process problem must be avoided, he says.

“The Verderflex range of peristaltic pumps uses the process of peristalsis to pump products through a hose in the same way blood, food and oxygen are pumped through the body,” he adds.

The pulsation effect of the pump results in solids being kept in suspension, which reduces the possibility of materials build-up in the pump. Further, rubber Verderflex hoses eliminate materials build-up in pump hoses, as these hoses are designed to increase life expectancy and performance.

Van der Walt notes that correcting the pH of a material is a precise process and the pump used for dosing must be accurate. He adds that peristaltic pumps have a linear flow speed and enhanced repeatability, making it the most accurate solution available.

“At the centre of resolving the AMD problem are water treatment plants – possibly the most important infrastructural requirement, which relies solely on the design and quality of the equipment installed.

“We can see the damaging impact that the problem has already had on the environment around us and we are working on a viable long-term solution. “It is a challenging task, but the commitment to contribute to finding an optimal solution, from suppliers like Verder, makes my job a little bit easier,” he concludes.