When the mine turned water positive after a few years of operation, Newmont decided to construct a 50L/s water treatment plant to treat and discharge excess mine impacted water collecting on site. The project consisted of a piloting and pre-feasibility phase, feasibility phase, execution and eventually Operations and Maintenance. Although a Zero Liquid Discharge (ZLD) Reverse Osmosis (RO) option was initially piloted, subsequent value engineering indicated that a simpler form of brine treatment would suffice to control the water balance. The water treatment plant consists of pre-treatment, Ultra Filtration (UF), RO and brine treatment.
Project Timeline
Phases
Piloting Phase
During this phase of the project, a variety of technologies were evaluated by using Miwatek’s aqueous chemical models. Ettringite; nitrate removal through biological processes; a ZLD RO process and a simplified RO with brine treatment processes were compared. The team decided to pilot the ZLD process as a proof of concept although later water balance modelling indicated that it was not necessary. A 15m3/hr pilot was deployed to site and a four-month pilot commenced.
Pre-feasibility Engineering
The pilot successfully proved the concept and provided all the data required for further stages of the project. The pre-feasibility study provided the trade-offs and suggested technology going forward.
Feasibility Engineering
The feasibility study expanded on the work completed in pre-feasibility to determine an appropriate cost estimate for the project (-10%+40%). Some key activities included Process Flow Diagram (PFD) development, datasheets, process description and interface definition.
Execution services
2016 - 2017. During this stage Miwatek worked with the client’s Engineering, Procurement and Construction Management (EPCM) consultant to execute the project. Miwatek developed P&ID’s, detailed engineering documents, bid evaluations, construction support and commissioned the plant.
Operation and Maintenance
2017 - Present. Miwatek was appointed to operate and maintain the plant. A team of 12 operates and maintains the plant on a 24hr basis.
