4.7 Water recycling - Tarkwa gold fields, Ghana

Technical Description

In this process, groundwater and wastewater from drilling operations are pumped into an underground sump. The sump water is raised in stages into a surface reservoir where it is mixed with raw water pumped from streams. The water in the reservoir is allowed to settle.

Through this process of dilution and sedimentation, water quality is improved, and the water is then recycled for use in underground mining operations.

This technology is described in Part B, Chapter 3, “Mining and Industry.”

Extent of Use

This technology is used by mining operations in the Tarkwa gold fields in Ghana.

Operation and Maintenance

This is a very flexible system, quick to install and designed to provide only a limited supply of process water to any location where water is needed. The pumps normally operate 10 hours per day.

Level of Involvement

This technology is industry-specific and is generally operated as part of the production process within the specific industry. Trained personnel are needed to maintain the pumping systems.

Costs

Costs are difficult to determine, but capital costs can be assumed to be high given the need for pumps, pipelines and related equipment. Operating costs, however, are probably similar or somewhat less than the costs of using raw water for the same operations.

Effectiveness of the Technology

And water supply. It has proven to be very effective in conserving water resources, while meeting the production demands of the industry.

Suitability

Water re-use systems can be installed in any sub-surface mining operation. The possibility of including a water treatment system within the pumping network, to upgrade water quality if necessary, is high.

Environmental Benefits

By containing the contaminated water generated in sub-surface mining activities, direct pollution of surface water resources is minimized. Contaminants are typically sediments and other dissolved chemicals which are amenable to removal using conventional treatment methods. However, the disposal of waste products should be monitored to limit negative inputs on the environment.

Advantages

Use of this technology limits the pollutant load to surface and ground waters.

Disadvantages

The technology, which is based on pumping, has a high energy demand.

Further Development of the Technology

The advantages to be gained from using this system depends on the quality of ore purification to be achieved, and the chemical processes used. Therefore, any future development of the technology has to be in the area of in-line water quality improvement.

Information Sources

Goldfields Corporation, Tarkwa and Ashanti Goldfields Corporation, Ghana.