Phase 1 HIA for the Seriti Arnot Water Treatment Plant Project

Large open cast mining operations at Seriti Arnot ceased in 1992. The area is currently undergoing mine closure rehabilitation as part of the fulfilment of the mine closure obligations. Since the ceasing of mine operations, mine impacted water emanating from Seriti’s mining area is conveyed through a water reservoir network to the final void dam. From the dam, water is pumped to evaporators which are used to dissipate decant water for irrigation purposes. The high energy and maintenance requirements of the mechanical evaporation is problematic due to the high costs associated with the system.
The Arnot OpCo mining area, recently acquired from Exxaro, consists of an underground and two open cast mining sections which have recently been closed. At Arnot OpCo, decant water from the Schoonoord area is managed through pumping from boreholes and shafts to U3 Dam. At the Mooifontein opencast area, decant water is pumped from the West to the South Pit resulting in a circulatory flow of water.
As part of the mine closure requirements, Seriti and Arnot OpCo are responsible for ensuring that mine impacted water is properly managed prior to discharge to either the local catchment or to a nominated and acceptable end user. Management of decant water may necessitate treatment intervention to ensure that the water does not have a detrimental impact on the surrounding environment or downstream water users. Due to the institutional arrangement between the coal miners (Seriti and Arnot OpCo) and the coal consumer (Eskom), the financial liability of mine closure is held by Eskom.
A pre-feasibility study conducted in May 2018 investigated various treatment options and proposed a treatment train consisting of a centralised Lime Softening, Ultrafiltration and Nanofiltration as the go-forward water treatment solution. The CWTP was to be situated near the previous Seriti mine area and required to be designed for a capacity of approximately 12.3 Mℓ/d, abstracted from both Seriti and Arnot OpCo.
The water treatment and conveyance systems include the following major units:
• A decant water abstraction system
• A decant water conveyance system
• A Combined Water Treatment Plant (CWTP)
• A treated water conveyance system
• A waste and solids handling system
• Requisite access roads and associated security infrastructure
• Requisite electrical and commercial and industrial (C&I) infrastructure
The development will also require road, stream and railway line crossings. Eskom power lines are also found within the pipeline route and will be negotiated with Eskom prior to construction.