The Pueblo Viejo mine is one of the largest gold mines in the world. The mine is located in Azua Province, south of the Dominican Republic. The mine has estimated reserves of 25.3 million oz of gold and 120 million oz of silver.

in 2008, Napier-Reid provided a demineralized water treatment system for the aforementioned mine to treat surface water for industrial usage, with a peak flow rate of 240 m3/day. The water treatment system includes multimedia filters, a polymer feed system, a packed bed cation column, a packed bed anion column, a sulphuric acid regeneration system, and a caustic regeneration system. Napier-Reid supplied all the pressure vessels and pipes. All the vessels were designed, fabricated, and tested as per ASME codes.

Feed water is pretreated with polymer to produce flocs of suspended solids, water then flows into two parallel multimedia filters equipped with two common air-scour blowers (one duty and one standby). Each filter performs in down flow filtration, all controlled by a PLC system. Filtered water from the storage tank is used to backwash filters. The filtered water then enters the demineralization system to produce demineralized water, which finally flows to a storage tank.