In recent years, Latin America has become a major player in the mining industry worldwide. Many engineering, procurement and construction management (EPCM) companies are developing projects for mining companies that operate in Chile and Peru—where the portfolio, just for copper projects, will total about $70 billion in the next few years.
Each project must include a guaranteed source of water to provide the daily requirements for its process and the financial viability of the companies involved. However, because of the large number of projects that are simultaneously being developed in the area and the huge volumes of water involved with each one, water sourcing is a major challenge. Many factors influence the water challenge, including:
- Environmental concerns
- Water scarcity
- Community conflicts
This has pushed engineering and pump companies to examine and take the initiative. They must find new solutions that can optimize the need for fresh water, while avoiding any environmental or social concerns.
Recycling water during mining operations is a first solution for water scarcity issues. Process water stored in reclaim ponds is one source and another is water that is dewatered during open-pit operations.
Every day, meeting the water supply needs becomes more difficult for mining companies. Therefore, recycling process water has become an opportunity to guarantee a sustainable supply system. This can be achieved by the design of a closed-loop recycling circuit that includes a reclaim water pumping system that allows the wastewater to be fed back to the start of the process. A well-designed reclaim water system can reuse up to 80 percent of the process water.
To minimize water loss, an efficient design should consider reducing water surfaces to minimize evaporation, as well as prevent contact between the pond and the ground through the use of High-density polyethylene (HDPE) geomembranes, reducing losses related to water filtration.
Vertical turbine pumps represent an ideal solution for this application because of their performance versatility, multistage nature and length design flexibility (see Image 1). Several variables must be considered for selecting the right equipment, including fluid characteristic—such as solids concentration and chemical composition. (For more details, please read “Reclaim Water Pumping,” Pumps & Systems, March 2012)
|Image 1. A reclaim water system employing a 1,400-horsepower pump|
An open pit mine is a type of surface mining. The top layers of the land are removed until the rock or mineral is visible. This creates a gigantic, open hole—or pit—that keeps getting deeper until groundwater appears, which makes it impossible for machines to continue working in the bottom of the pit.
|Image 2. A dewatering pumping system at work in an open pit mine in northern Chile|
Mine water is subject to cyclic and climatic conditions, such as rainfall, which can be particularly important in South America’s central Andean region where highly intense rains and thunderstorms occur from January through February, called the altiplanic winter. These rains and storms are due to the moist air that comes from the east (where Bolivia and the Amazon are located) and brings unsettled weather and occasional snow.
Pit ﬂoor sump pumping and adequate booster facilities to remove surface water inﬂow and other water accumulation in a timely manner is often an essential requirement, depending on the specific mine setting. Effective dewatering operations create dry conditions so that the earth can be safely excavated, reducing drilling and blasting costs. Additionally, wear and corrosion on equipment is minimized, further reducing operational costs.
The most effective way to accomplish an efficient dewatering system is with a complete engineered heavy-duty dewatering package (see Figure 1), which includes modular barge pumps and booster stations. Engineered barge pump systems with vertical turbine pumps can deliver high heads up to 300 meters or 984 feet, which eliminates the need for an immediate booster station. They should be installed in the next higher mine bench level, diminishing the equipment used in the mine pit.
One important consideration is that this mixture of underground and surface wastewater has not previously been considered for use in the process. However, depending on the quantity and quality of groundwater collected, it can become an important available water resource for operations.