A R74-million desalination plant was commissioned by South32 in September 2016 at their Hillside Aluminium smelter in Richards Bay, KwaZulu-Natal. The plant will remove minerals from seawater abstracted from the Richards Bay harbour, thus enabling the company to maintain operations during a time of persistent drought, where the current water crisis has resulted in the implementation of stringent water restrictions in the Richards Bay domestic and industrial sectors.
In March 2016 Level 4 water restrictions were put in place by the uMhlathuze Municipality and although South32 and JG Afrika had for some months been discussing the need to investigate methodologies to reduce or reuse current water supplies, it then became clear that an alternativeto municipal water supply urgently needed to be found to ensure continuous smelter operations. The knock-on socio-economic impacts on the local, provincial and national economies would be dire if the smelter plant were to close: a loss of up to 10% of the GDP in the region, a potential loss of 20 000 jobs in the country directly or indirectly affecting the livelihoods of around 80 000 people, and the need to import aluminium into South Africa at a cost of some R4,1-billion per annum.
The desalination of seawater was identified as the preferred alternative to relying on the municipal water supply.
JG Afrika recommended NuWater as a technology partner and the team soon got to work fast-tracking investigations and conceptual designs for the installation of a desalination plant, utilising membrane technology, to produce process water at Hillside. The urgency of the project required the engineering team to focus on the existing infrastructure and mechanisms owned by South32, Foskor and Mhlatuze Water, where use could be made of current licences, waste discharge permits and structures.
Foskor, a producer of phosphates and phosphoric acid, uses existing abstraction infrastructure at Richards Bay harbour. This seawater abstraction provides Foskor with an emergency alternative supply of process water for the Mondi effluent it uses under normal operations. The Foskor extraction point is designed for a capacity of 1 250 m3/h. Foskor’s current estimated demand for seawater is 700 m3/h and this created the option to partner with them to deliver 280m3/h to Hillside while remaining within the current licensed approved limit of 1 250 m3/h.
The exiting abstraction infrastructure has two concrete pump chambers of which only one is in use. Foskor and South32 reached an agreement whereby South32 would add a second pump within the vacant chamber, sharing a portion of the existing rising main, to abstract the seawater required to keep the smelter operational during municipal water supply interruptions. A new 2,3-km-long Dia 355-mm HDPE pipeline traversing the area between the harbour abstraction and Hillside was constructed inside and alongside the South32 raw material conveyors.
The upside of this agreement was that most of the infrastructure and some of the pipeline to transfer seawater from the harbour to Hillside was already in place or could be installed within the existing conveyor servitude, significantly speeding up the implementation and construction programme. The raw water pipeline route was identified, designed, constructed and commissioned in 24 weeks.
Another identified benefit and its positive impact on the implementation programme was the existing concrete slab within the Hillside complex and its relative proximity to the Hillside process water storage reservoir. This, together with a fully containerised modular plant designed, supplied and installed by NuWater, comprising raw water clarifiers, ultra-filtration and finally reverse osmosis (with an output capacity of 2 Ml/day of process water) kept the civil construction requirements at the plant to a minimum.
As with any desalination technology, the disposal of brine as a waste product was a challenge. Again the lateral thinking of the South32 and JG Afrika team identified an existing 1,5-km-long pipeline between Hillside and the decommissioned Bayside smelter. This existing Dia 300-mm pipeline required minor refurbishment and a 335-m-long extension to connect the Bayside smelter into the existing Mhlatuze Water licensed discharge sea outfall.
JG Africa was appointed by South32 as the principal agent for the project and was responsible for all civil engineering works, raw water pipeline, pump selection and brine pipeline designs. The project was completed in an astonishing 28 weeks from inception and concept identification to final delivery of 2 Ml/day of process water to the South32 Hillside smelter.
