A water management program needs to not only focus on recovery, but also on conservation, environmental impact, and planning. Water is integral to aggregate operations. As the need for aggregates continues, the need for water is necessary.
“All water should be recycled from tailings ponds, runoffs, and wheel washes whenever possible,” says Lance Griffin, director of aggregate operations for Cemex in Texas and New Mexico. “You should always look for ways to better manage and conserve this limited natural resource within your operation.”
Follow solid engineering practices by keeping a plant’s flow, design, and operation simple. “Prepare for breakdowns by making the plant as simple to repair as possible and look at current and future water needs,” Griffin says. “Many water recovery plants are undersized and don’t perform to expectations. A complete water audit is a great place to start when considering a water management system.”
At LafargeHolcim, water management plans in place are reviewed every five years to get a better understanding of consumption. Water flow diagrams are put together, indicating all points of consumption.
“Plants change, operations change, and things move around,” says Joel Nickel, head of land and environment in the United States for LafargeHolcim. Reviewing the plans and water flow provides an accurate snapshot of water consumption. “It has provided good learning,” Nickel says. “We have found leaks in water lines. Repairing those has made a big difference.”
Nickels points out that, at one operation, nearly 1 million gallons were saved by repairing water leaks. “We recognized through metering of water that we were consuming more water than we were putting through the plant,” he says. “By doing a diagram, we found water was going somewhere we didn’t know.”
Now, the level of awareness about water management and its importance is quickly being raised as an industry, especially because it is quantifiable, explains Tom O’Brien, engineer and consultant for Paschal Associates LLC. “Fifteen years ago, it was just dirty water,” he says. “Now, it has become a cost center and a point of focus. We can now evaluate a plant’s waste effluent (stream) and create a model for necessary fines recovery equipment, including capital and operating costs.”
Ultimately, good water management can contribute to a producer’s bottom line. Although there may be an initial investment in the equipment necessary for fines recovery, there is a return on invest because there is a lower operating cost in handling all the water, O’Brien says.
“Some of the larger operations I service will use up to 35,000 gallons per minute,” O’Brien says. “If you are not using some kind of recirculating system, that is a lot of water. The amount of waste or mud washed off can be as high as 500 tons per hour. When you get into those volumes, it just makes sense to recirculate it.”
Effective Water Management
Lance Griffin is director of aggregate operations for Cemex in Texas and New Mexico. He is a Penn State mining engineer with more than 35 years of experience in underground, surface metal, and non-metal mining operations. He resides in New Braunfels, Texas.
Tom O’Brien is an engineer and consultant for Paschal Associates LLC. He is a graduate of Penn State University with a degree in mining engineering. He has 25 years of experience in the water treatment and equipment side of fines recovery.
Joel Nickel is U.S. head of land and environment for LafargeHolcim. He has been with the company for 10 years and focuses on improving the business and best practices to make it more compliant and sustainable.
Voices of Experience
A t the Cemex Balcones Quarry, the operation recently installed a water recycling plant to protect critical local water resources and supply the Balcones wash plant with consistent wash water for its aggregate plant.
Lance Griffin, director of aggregate operations for Cemex in Texas and New Mexico, says the company recognizes the importance of water to local communities such as the 2 million residents in the New Braunfels area where the Balcones Quarry is located. He says that although an emphasis on water management and conservation has been a high priority at the operation for many years, New Braunfels is one of the fastest-growing cities in the nation, according to the U.S. Census Bureau — making good water management a necessity. “Sustainability is integrated and embedded into our day-to-day operations and business strategy,” Griffin says. “A new water recovery plant was the right thing to do.”
The Balcones system uses proven technologies paired with what Griffin says is “common-sense” engineering and full automation. The plant consists of two 60-foot thickeners, two banks of cyclones — one bank for manufactured sand production and one bank for ultra-fines production — twin, 44-inch sand screws, a dewatering screen, pinch values, pumps, and a mixing and dosing system. All of the components were integrated into one automation platform, allowing for total plant control from any location. The water recycling system uses 90 percent less water annually than the previous quarry wash plant. It recycles 12,000 gallons of water per minute for use in the aggregate wash plant.
“Any organization looking to install a water management system needs to look at their current and future water needs,” Griffin points out. “Investigate existing plants, aquifers, and technology,” he adds. “Before planning the new system, companies should understand the applicable laws, regulations, permitting, and other requirements for local operation and design needs.”
The key takeaway when it comes to water management is to be proactive, says Joel Nickel, U.S. head of land and environment for LafargeHolcim. “Water will be a scarcity in the United States, if it isn’t already like in some parts,” he says. “It’s good for the industry to start working toward trying to recycle and reduce water consumption (rather) than be regulated in the future.”
One challenge is to find a uniform approach that works everywhere. “I look at the U.S. as 50 different countries with 50 different rules,” Nickels says. “We manage this by having tracking compliance documents in our environmental management documents that track the rules of each state.”
LafargeHolcim uses a six-step process as its water management (WM) protocol. First, comply with legal rules and requirements. Next, establish an operation water footprint. “Know how much water you are using, discharging and recycling,” Nickel says. Third and fourth, conduct a site-level assessment and establish corresponding action.
“After we understand where water is going, we want to see if there are any ways to improve it,” Nickels points out. “Be proactive and engage stakeholders. Talk to the plant guys, the local communities in which you operate, and local water districts to see if there could be any collaborations.”
To that end, the LafargeHolcim Morrison, Colo., operation stores water for the town. “It has a need for water storage, and we have an old pit,” Nickel says. “In the arid west, we are creating reservoir space in mined-out sand and gravel operations.”
Performance improvement is the fifth WM protocol step. “Set parameters from a regional level and try to work with operations,” Nickels says. The sixth step is to regularly review WM plans and make changes where necessary. “We review the plans and flow diagrams every five years,” he adds, noting that updates ensure accuracy.
Compared to other mineral industries, the aggregate industry is still relatively young when it comes to fines recovery and treatment. “Prior to the last 20 years, the aggregate industry did not need to use any kind of water treatment for fines recovery,” says Tom O’Brien, mining engineer and engineer/consultant with Paschal Associates LLC. “In the last 20 years, we have been forced to do it. Some of the reasons are economic, real estate, and environmental.”
The industry’s slow adoption of fines recovery and water treatment is also a result of its fractionation.
“Our industry is so diverse and spread out,” O’Brien says. “There are rock quarries all over the U.S. These quarries are owned and operated from large corporations all the way down to small, family-owned operations.” For these reasons, fines recovery and water treatment are more slowly being incorporated as best practices.
Water management essentially breaks down into two overall categories – discharge water and processed water, O’Brien says. “If more water is generated than a quarry can hold, it has to be removed from the property,” he says. “In some cases, that water has to be treated with specialty chemicals and must be discharged in conditions in accordance with the government.”
Water used to wash aggregate to meet state specs must also be dealt with; what producers do with this processed water varies. “Fifty years ago, quarries were putting the water into a big pond or somewhere where the fines would settle and the water would recirculate,” O’Brien says. “Now, environmental regulations have become more stringent, and there are more liabilities to using big settling ponds — and they have to be repeatedly cleaned.”
Economics plays into water management. “Water is a resource, and it is monitored in certain areas,” O’Brien says. “How much water you pull out of the ground becomes an economic driver.”