Mining activity entraps sand, ore particles and suspended solids in the water that flows from the stopes. The entrainment of solids in the mine’s process water threatens the effective operation of the mine’s underground water reticulation system.

Typical problems that occur include:

• costly replacement of hydro-powered equipment and pumping infrastructure
• silting of clarifiers and storage dams
• costly repairs of downstream infrastructure and processes when blockages occur
• flooding of underground mining operations due to infrastructure failure

Good grit separation not only prevents problems in the mine water reticulation system, but the grit has also entrained monetary value as it contains extractable minerals of value.

Grit removal is complex because of the varying quantity, size, density, SG and structure of the suspended material.

De-gritters are used for the separation and removal of gravel, mineral particles and larger suspended solids from the mine water. The working principle of de-gritters is based on the application of gravity forces, or varying particle settling velocities.

Removing 2 tons of suspended solids every day

Watercare Mining built and commissioned a high-flow de-grit plant in a deep level gold mine in South Africa resulting in significant savings in transfer pump replacement and repairs, clarifier and clear water dam maintenance and cleaning.

The design of the de-grit plant is tailored to the conditions of the mine. The plant is small enough to couple into the existing water reticulation system and haulage.

The 400 l/s high flow de-grit plant removes suspended solids from 75 microns (with 80% recovery) to 125 microns (with 90% recovery) and can tolerate a maximum feed solid load of 5%. Conventional de-grit systems target a solid cut size of 250 to 300 µm (with 90% recovery).

The high-flow de-grit plant removes two tons of solids (grit) daily from the mine water. Dam maintenance and cleaning, as well as pump maintenance and replacement, were reduced significantly, with associated cost savings.

The clear water is returned to the mine’s water reticulation system and flows to the settler for removal of the sub 75 µm particles. The treated mine water ultimately recycles and recirculates through the mine’s water reticulation system.

The high flow de-grit plant is a key component of Watercare Mining’s integrated solid handling system. When commissioned together with Watercare Mining’s High-rate Clarifier, and Automated Powder Dosing System, suspended solids in the settled mine service water are consistently reduced below 50 mg/l.

• The images used in this post show a 400 l/s high flow de-grit plant installed and commissioned into the existing haulage of a deep-level South African gold mine.