Mining

Seriti New Vaal Colliery

The New Vaal Colliery (NVC) sits on the banks of the Vaal River, immediately south of Vereeniging in the Free State Province. The colliery employs opencast strip mining to produce 18 million tons annually of low-grade coal, which is supplied exclusively to Eskom’s 3700 MW Lethabo Power Station adjacent to the mine.  Previously owned by Anglo American Thermal Coal, the NVC was bought by Seriti in 2018.

Problem

As a nett water positive mine, NVC deposited and stored mine wastewater from various pit watering operations, production process and rainfall runoffs into an 8200 million litre reservoir where it was left to evaporate.

With the reservoir fast approaching maximum capacity, Anglo American Thermal Coal urgently needed to implement a water treatment solution that would prevent wastewater contaminating the Vaal River, which is not only a vital source of water for industry and agriculture but supports 12 million consumers in and around Gauteng, South Africa’s economic heartland.

Solution

Mobile, modular and scalable, NuWater’s high performing wastewater treatment plants provided a smart solution capable of addressing NVC’s immediate and long term needs.

The initial phase of the project involved the design, manufacturing, installation and commissioning of the first 4 MLD of a total 20 MLD treatment capacity in an unprecedented time of 6 weeks – effectively addressing the rising reservoir levels and preventing an environmental disaster.

This was immediately followed by the addition of 4 MLD plant capacity every 4 weeks to achieve the contractual design treatment capacity of 15 MLD. The high-quality process water produced from the plant was pumped to Lethabo Power Station to reduce daily abstraction from the Vaal River.

Results

Despite being designed and manufactured to produce 15 MLD of high quality process water, smart process optimisation and utilisation of NuWater’s water treatment rental fleet enabled capacity adjustments from anywhere between 10 MLD to 20 MLD over the last 8 years.

NuWater’s wastewater treatment plant not only successfully dealt with extraordinarily dynamic deviations in the wastewater, but ever changing product qualities and quantities required to align to the fluctuating mining schedule and seasonal rainfall.

In addition to reconfiguring the plant into a partial two pass Reverse Osmosis system, Nuwater dealt with periodic spikes in the aluminum concentration through inline acid dosing to lower the pH pre-Ultra Filtration and adjusting Ultra Filtration operational parameters to effectively remove the precipitated aluminium, thereby avoiding further catastrophic aluminum fouling in downstream membrane processes.

Built, owned, operated and maintained by NuWater, the plant continues to treat wastewater with an EC far in excess of the contractual maximum and has produced in excess of 27.5 billion litres of water in 8 years of operation.