|Sourcebook of Alternative Technologies for Freshwater Augmentation in Africa (International Environmental Technology Centre - United Nations Environment Programme, 1998, 182 p.)|
|Part C - Case studies|
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 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.
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.
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.
Use of this technology limits the pollutant load to surface and ground waters.
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.
Goldfields Corporation, Tarkwa and Ashanti Goldfields Corporation, Ghana.