As an innovative response to the need for water conservation, anthracite producer Zululand Anthracite Colliery’s (ZAC’s) wastewater reverse osmosis (RO) treatment plant will provide clean drinkable water to about 240 families in the surrounding communities, as well as contribute to the mine’s conservation efforts.

ZAC collaborated with water purification company Dyad Group for the design, installation and commissioning of the water treatment plant – a process which took just over five months to complete.

The plant is designed to treat 240 000 ℓ of wastewater from the mine’s operations every 24 hours with the RO technology removing total dissolved solids and organic and inorganic matter, making the water potable.

ZAC points out that according to the Department of Water and Sanitation (DWS), South Africa is a water-scarce country with an average rainfall of 465 mm, which constitutes half of the global average. In recent years, ZAC also highlights that KwaZulu-Natal (KZN) has faced a water security crisis, with the South African Weather Service’s monthly drought bulletin illustrating a drop in KZN’s average dam levels between 2023 and this year.

On June 10, 2023, KZN dam levels were recorded at 90.8% and dropped to 90.7% during the same period this year, prompting the DWS to urge KZN residents to use water sparingly.

ZAC’s water treatment plant is innovative and sustainable, having the dual benefit of reducing the mine’s waste footprint and generating additional supply for host communities.

The plant has the capacity to supply about 240 families with water, based on the average use of 1 000 ℓ/d a household, notes Dyad Group project manager Samantha Chigwedere.

The mine embarked on the project to ramp up environmental efforts, states ZAC project manager Howard Atkinson.

The commitment ZAC has made to conserve water and reduce its wastewater volumes played a pivotal role in the decision to install the RO plant, he adds.

Treatment Process

The wastewater flowing from ZAC’s Outcrop, Deep E and Ngwabe operations is captured in a reservoir, whereupon it is treated through the RO plant.

Normally, such water would be recycled back into the mine’s coal processing cycle, however, ZAC decided to take it a step further by making it potable.

The water is initially pumped into a 84 m3 raw water reservoir, through a chemical composition-monitoring and control system, to a flocculant automatic dosing system and then to a clarifier, where the suspended matter is precipitated.

The heavy matter coagulated settles at the bottom and cleaner water will overflow into reservoir tanks.

From collection tanks, there are an array of filtration media and softeners, ensuring the removal of remnant suspended solids, odours, inorganic and organic matter.

After filtration and softening, water is then pumped to the RO system, which is specifically designed for the mine’s wastewater quality of purification. After the RO plant, the water flows to a treated water reservoir and is disinfected to ensure that the water is safe to be consumed by humans.

“We use chlorine dioxide which is the preferred method of disinfection according to the World Health Organisation. Chlorine dioxide provides a prolonged residual disinfection efficacy,” explains Chigwedere.

She further elaborates that it continues to be effective even with the concentration as low as 0.1 parts per million, and will maintain the efficacy over a wide chemical composition range and, unlike chlorine, does not produce reaction by-products.

Chigwedere adds that the plant will be periodically maintained to ensure that it performs optimally, with a full-time plant operator that will monitor and conduct daily water tests on site.

The initiative will increase capacity to ZAC’s pipeline which has supplied water to the community over the years.

As of April, 31.47-million litres of water were delivered to the community through the existing waterworks, while a total of 88.98-million litres was provided in 2023.