Processing, Usage and Recycling Challenges at Quarry Operations.
By Mark S. Kuhar
Water: Quarry operations need it. Municipalities protect it. Community members worry about it. Congress legislates it. Manufacturers devise ways to utilize it to the benefit of everyone. The balance between too much and not enough is often difficult to achieve.
Every time you turn around there are news reports about quarry operations and water. Indeed, water always seems to serve as a bone of contention whether in operations, permitting or environmental concerns.
For instance, Kraemer Mining & Materials Inc. in northwest Burnsville, Minn., operates just south of the Minnesota River. The mining operation requires dewatering of the quarry, and Kraemer is now pumping approximately 10 million gal. a day (3.6 billion gal. per year) into the Minnesota River. A water appropriation permit obtained from the Minnesota Department of Natural Resources a decade ago allows for the discharge of four billion gal. a year, a figure the quarry is approaching. Kraemer would like to expand its operations, but it would require the pumping of greater volumes of water than are allowed under its permit. But will the operation be able to get that permit?
Proposed plans to expand Martin Marietta Materials’ Rocky Point Quarry in Pender County, N.C. – a move that would reportedly impact dozens of acres of wetlands and other waters on the property – remain on hold as state environmental officials await further information on the project, according to Coastal Review Online.
In Wilmot Township, west of Kitchener, Ontario, Canada, residents are asking why the township is continuing to extract aggregate below the water table. The township’s continued extraction below the water table sets a dangerous precedent for future aggregate project applications, contradicts the Region of Waterloo and, creates adverse conditions for protecting a critical water asset, the Waterloo Moraine, according to The Record.
Hopkins Hill Sand & Stone LLC, a Rhode Island quarry on New London Turnpike that borders the Big River Management Area, has reportedly been operating without a pollutant discharge elimination system permit for 16 years, according to ecoRI News. The main objective for any activity that is allowed on the Big River Management Area is the protection of drinking-water quality, according to a 1996 land-use study of the conservation area. The study also noted that land use shouldn’t adversely impact water quality and must consider the impact a use has on the environment and proper maintenance of plant and animal habitat, the publication noted.
A CreekWood Resources quarry that’s being proposed just north of Opelika, Ala., is causing concerns for residents and city leaders. The proposed location is on County Road 168, just off U.S. 431, but dozens of people are speaking out against the quarry citing concerns about air and water quality, according to WSFA 12 News. “CreekWood Resources will not release any pollutants into the air or surface waters; our operations will not impede groundwater aquifers; and we will not damage any structures in the area,” the operation said.
According to WZTV in Nashville, some Coffee County, Tenn., neighbors are upset over a proposed Hawkins Asphalt and Paving rock quarry in Beechgrove, Tenn. A water-quality expert said he and others are worried about the environmental impact the quarry could have on surrounding waterways, wildlife and air quality.
The Hillsborough Township, N.J., planning board approved plans for the construction of a new facility where the applicant, Constructural Dynamics Inc. (Gibraltar Rock of Belle Meade) sought minor site plan approval to construct a process basin to collect, clarify and recycle the process water for reuse in its stone washing operations, in compliance with the New Jersey Department of Environmental Protection (DEP), according to centraljersey.com.
The Colorado Bureau of Land Management has delayed the potential start date of an environmental review into the expansion of a Mid-Continent limestone quarry until next year. “We are looking at some time in 2021 to begin the (environmental impact statement),” said BLM Spokesman David Boyd. The proposed expansion of the Mid-Continent quarry, owned by Rocky Mountain Industrials Inc, has drawn criticism from many residents of the nearby Glenwood Springs, Colo., area in the past two years. According to a report on the Post Independent website, RMI would like to expand the limestone quarry’s operational size from about 23 acres to 321 acres. The local news site report states that, “Currently, the BLM is conducting an environmental assessment of five wells RMI needs to drill to conduct a hydrological study. That study must be underway before the review of the larger quarry expansion proposal can begin.”
The stories go on and on.
Waters of the United States
While operations work through their local water issues, the U.S. Environmental Protection Agency (EPA) and the Department of the Army finalized the Navigable Waters Protection Rule to define “Waters of the United States” establishing federal regulatory authority under the Clean Water Act.
For the first time, the agencies are streamlining the definition so that it includes four simple categories of jurisdictional waters, provides clear exclusions for many water features that traditionally have not been regulated and defines terms in the regulatory text that have never been defined before.
Congress, in the Clean Water Act, explicitly directed the agencies to protect “navigable waters.” The Navigable Waters Protection Rule regulates these waters and the core tributary systems that provide perennial or intermittent flow into them.
Under the final “Step 2” rule, four clear categories of waters are federally regulated:
- The territorial seas and traditional navigable waters.
- Perennial and intermittent tributaries to those waters.
- Certain lakes, ponds, and impoundments.
- Wetlands adjacent to jurisdictional waters.
The final rule also details 12 categories of exclusions, features that are not “waters of the United States,” such as features that only contain water in direct response to rainfall (e.g., ephemeral features); groundwater; many ditches; prior converted cropland; and waste treatment systems.
The final rule clarifies key elements related to the scope of federal Clean Water Act jurisdiction, including:
- Providing clarity and consistency by removing the proposed separate categories for jurisdictional ditches and impoundments.
- Refining the proposed definition of “typical year,” which provides important regional and temporal flexibility and ensures jurisdiction is being accurately determined in times that are not too wet and not too dry.
- Defining “adjacent wetlands” as wetlands that are meaningfully connected to other jurisdictional waters, for example, by directly abutting or having regular surface water communication with jurisdictional waters.
“For small businesses like mine, regulatory uncertainty and inconsistency result in real costs,” said Alan Parks of National Stone, Sand and Gravel Association (NSSGA) member Memphis Stone & Gravel. “The new WOTUS definition continues to protect our nation’s water and provides clarity on several key exclusions such as ponds built on dry land, pits and basins associated with mining, and streams that only convey water after storm events. Knowing that our gravel pits and water treatment basins won’t carry an additional federal regulatory burden is very helpful. These changes will allow us to be even better stewards of our local natural resources, which results in a positive benefit to our community.”
“The scope of federal jurisdiction over waters has been confusing for years, causing permitting delays. The implementation of the 2015 WOTUS rule made matters worse,” said NSSGA Environmental Committee Chairman Mark Williams of Luck Companies. “We are pleased that the new rule provides important environmental protection of waters that need it most, while ensuring clarity to aggregates producers like Luck. It’s important that both the regulators and NSSGA members are able to understand when a federal permit is required, so we can continue to provide materials for vital infrastructure projects.”
“NSSGA members have worked for years to get a WOTUS rule that aligns with congressional intent by providing necessary protections while allowing aggregates producers the regulatory certainty by which to plan and operate their businesses and provide the necessary infrastructure projects America needs,” said NSSGA President and CEO Michael W. Johnson.
But 15 conservation groups are challenging the rule, filing suit in South Carolina federal district court. “This rule effectively guts the Clean Water Act by permanently removing protections for approximately half the nation’s streams and wetlands,” said Jim Murphy, director of legal advocacy for the National Wildlife Federation. “It should be shocking, but it isn’t, that the EPA did not examine the impacts of this rule on water quality or public health. The agency has openly admitted it did not do a substantive analysis of which streams and wetlands would lose protections and which pollution permits would be invalidated as a result. We think the courts will agree that federal rules should be based on sound science and that this one is not.”
Manufacturers to the Rescue
As quarry operations deal with the outside impact of water issues, inside the quarry, water use, reuse and retention are big issues whether it is in the areas of processing, land conservation or dust control. There, it is equipment and technology to the rescue.
CDE unveiled its new 500-tph Combo X900 at this year’s ConExpo-Con/Agg show in Las Vegas. The X900 is the latest in CDE’s range of Combo all-in-one wet-processing and water-management solutions. “With our new Combo X900, we’ve doubled its capacity and created a next-gen solution for materials processors across North America and Latin America,” said Kevin Vallelly, director of engineering at CDE. “The Combo X900 can process 500 tph of feed material, including natural sand and crushed rock, containing unwanted clay, silt and other organic contaminants to extract quality in-spec washed and graded sand products that are market-ready straight from the belts.”
As well as its increased capacity, the Control Cabin of the new Comb X900 has been repositioned to sit on top of the water tank, a design decision Vallelly says is directly influenced by the North and Latin American markets. “In these regions, plant and machinery are subject to major temperature extremes and fluctuations,” he said. “By positioning the Control Cabin on top of the water tank we’re able to better protect the operational heart of the plant and offer a solution that can be adopted throughout both North America and Latin America where high and low temperature extremes are recorded.”
Furthermore, where traditional washing systems typically have a separate standalone water tank, the new Combo X900 has integrated this into the design of the AquaCycle thickener tank resulting in a peripheral wall for water storage, which has significantly reduced the overall footprint.
It provides customers with almost total independence of water supply and minimizes the requirements for costly site engineering due to its significantly smaller footprint which is, on average, 30% smaller than other traditional wash plant setups.
Vallelly said, “Traditional washing systems would typically consume up to 15 times more water than that required for the Combo X900. Our best-in-class water management and on-board water recycling minimizes costly water consumption and ensures up to 90% of process water is recycled for immediate recirculation through the closed-circuit system. The Combo X900 enables materials processors to wash more than 500 tph with only 800 gpm, about the same amount of water that would be required to wash a truck.”
With its single chassis design, the Combo X900 incorporates all essential processes – washing, dewatering, water recycling and stockpiling – onto one single, interconnected and pre-assembled unit. A plug-and-play system, it arrives on site pre-wired and pre-tested, ready to process material within just five days as a standalone plant or as part of a larger turnkey solution.
Clearwater Provides Customized Clarification
Wissota Sand & Gravel installed a stationary water clarification system manufactured by Milwaukee-based Clearwater Industries, which provides turnkey solutions, site and water analysis, chemical selection and complete systems that are custom-designed for each specific sand and gravel application.
Clearwater Industries engineers a clarification system that allows operations to take a dirty water stream and produce clean water immediately, while concentrating the fines or solids to a thick state.
To obtain a greater compression of mud and a drier consistency, the systems features two tall, cylindrical aging tanks with internal mud rakes, combined with a dry polymer feed system, hydraulic package, control panel and mud discharge pump.
Clearwater adapted its equipment to accommodate their existing cyclones, which are mounted on top of the clarifier. The cyclones spin out the sand, or plus-200-mesh material.
Water, containing fines, overflows the cyclones and enters the clarifier where it is treated with flocculants, forming solids which settle to the bottom. Clean water continually overflows the top of the clarifier and is recirculated back to the clear water pond that supplies the plant. Then the solids are pumped and discharged via a 10-inch pipeline to a pond where residual water weeps off the mud and runs into a low point.
At the end of the season, the residual water is pumped back into the clean water pond, and the mud is used in reclamation.
Clearwater Industries, clearwaterind.com
Eagle Iron Works Debuts Brand New Piece of Equipment
|Eagle Iron Works|
Eagle Iron Works (EIW) has offered customers reliable, easy-to-operate equipment to handle washing and classifying applications since 1872. During ConExpo-Con/Agg, EIW showcased the latest piece of equipment in its expanded product line. The new Eagle Dewatering Screen was displayed in combination with a CONDOR Screw Washer, also shown for the first time at the show.
Introduced to the market in early 2018, the CONDOR has been providing aggregate producers with Eagle-quality dewatering for the past two years, with many active installations. Now, this equipment can benefit from the addition of Eagle’s new Dewatering Screen for an even drier product.
Designed to fit under the discharge end of any brand of screw washer, the Eagle Dewatering Screen improves final product dryness for quicker sale. It is built on a structure that allows for the addition of a pump and sump to return process water back to the screw, reducing your site’s overall water footprint.
The Eagle Dewatering Screen can be purchased as a combination with an Eagle Screw Washer or purchased individually, easily fitting into your existing site to create a drier product while saving on capital costs and giving faster return on investment.
Kolberg-Pioneer Launches Water Clarification Systems
Kolberg-Pioneer Inc. has partnered with Tecnoidea Impianti to offer water clarification systems in North America.
The clarification systems accelerate the process of filtering fines from dirty water for reuse in the processing plant. These systems are designed to eliminate the need for large and expensive settling ponds by recovering up to 95% of the water that flows to the clarification system. This allows producers to use significantly less water in their system.
“Water clarification systems save producers time and money associated with building, using and maintaining settling ponds. This partnership with Tecnoidea Impianti will allow us to continue to offer a one-source solution for our customers,” said Brett Casanova, washing and classifying product manager for Kolberg-Pioneer.
The water clarification systems will include flocculation preparation units, static vertical settling tanks, thickened sludge tanks, side and overhead beam plate presses, and other accessory components.
McLanahan Offers UltraWASH
McLanahan Corp. showcased the newest size range for its UltraWASH Modular Wash Plant at ConExpo-Con/Agg, marking the first time that the UltraWASH 6505 will be displayed at a show.
McLanahan has carefully thought of all the details and features that will make maintenance and efficiency easier – including two truly unique, patent-pending features. The patent-pending Eze-Riser allows the operator to cut pump maintenance time in half, and the patent-pending Fines Forward Slide and Aggregate Discharge Hood are included to increase operational efficiency.
The patent-pending Eze-Riser works together with the pump service trolley to enable safe and efficient pump maintenance, such as changing the impellers or replacing the casing liners. A foot pedal lifts the discharge pipe from the pump and utilizes a locking mechanism to then holding the pipe aloft, offering the clearance needed for the pump to roll out on the trolley service platform unrestricted.
Sufficient flexibility is provided by the hydrocyclone entry hose bend above to accommodate these few millimeters of pipe travel, making it unnecessary to disturb pipework other than where it connects directly to the pump at its suction and discharge flanges.
The manually adjustable Fines Forward Slide can divert a portion of raw fines into the coarse sand processing stream. This balances the downstream process to optimize plant capacity. Alternatively, by substituting the last row of fine material screen panels with coarse material screen panels, the Fines Forward Slide will allow alterations of the proportions of fine and coarse decking areas above, while still preventing the loss of coarse material into the fines processing stream. Two men (one each side of the sizing screen) are all that is required to simply reposition the Fines Forward Slide eliminating the use of cranes or other lifting equipment.
Washed aggregate is discharged from the end of the sizing screen in up to three discrete size fractions for separate stockpiling. However, any two adjacent – or indeed all three – aggregate product sizes may be recombined (either for consolidated stockpiling or onward processing as required) simply by one man’s manual operation of the aggregate discharge/remixing hood’s rubber-lined diversion traps.
McLanahan also said UltraWASH is the only modular wash plant in the market to offer a sump conversion kit. With a sump conversion kit, you can quickly and safely change between a one-or-two-pump setup. The sand process can also be altered to process a single wash, a double wash or a two-product sand. So even if your process requirements change throughout your operating lifetime, you can modify the plant to suit to get the outcome that you need.
Superior Premiers New Screen/Wash Plant
Superior Industries Inc. showcased a newly configured portable wash plant at ConExpo-Con/Agg. Capable of producing as many as five products, the Portable Spirit Wash Plant carries a 6 x 20 Guardian Horizontal Screen, plus a sand production module and ultra fines recovery module.
- Material is fed to a slurry box, which liquifies it to improve the screening and stratification processes.
- The three-deck horizontal screen washes and sizes three products from a top, middle or bottom deck.
- Leftover sand is then processed through one of two Spirits Wash Modules. These modules consist of one or more Helix Cyclones followed by a dewatering screen.
- The first wash module uses a cyclone to size and separate material for a traditional sand product. A dewatering screen ensures it’s instantly salable off the discharge chute.
- Depending on the deposit, an optional ultra fines recovery module washes out -100 to -400 fines for microfine material, which is saved from being lost to a waste pond.
“It’s the first time such a configuration has been created for the portable market in North America,” said Matt Voigt, manager of portable plants at Superior. “We incorporated our low-profile dewatering screens and a series of hydraulically-powered components to ensure the plant is road permissible and quick to deploy.”
Applications for the new portable plant include operations with settling ponds, crushed aggregate, sand and gravel, dredging and frac sand.
Superior Industries, www.superior-ind.com
Terex Washing Systems Promotes AggWash
Terex Washing Systems (TWS) refers to its AggWash 60 wash plant as a “game changer in wash recycling.” AggWash 60 incorporates screening, scrubbing, sizing and recovery of sand on one modular chassis and produces up to six grades of saleable sand.
The AggWash was designed to address requirements for recycling customers and quarry owners, particularly in the construction, demolition and excavation waste recycling market. The high-performance solution has been designed to maximize yields from feed materials with efficiently designed system processes that keep running costs at a minimum. While its readily portable format makes it particularly suitable for green-field applications, contractor use and temporary planning permission sites, operators more used to static installations will still appreciate the small footprint and minimal site preparations required.
Paul McWilliams, TWS engineer manager, said, “In all cases, installation time is significantly less than conventional builds thanks to the high level of factory pre-fitting and connections. The no-compromise design ethos ensures maximum serviceability and performance despite numerous innovative features, including easily removed pumps, ready access to screening media and intuitive controls.”
TWS showcased Terex FM UltraFines at ConExpo-Con/Agg, which is a crucial step in efficient management and recovery of ultra-fines material from wastewater streams produced from washing processes, according to the company.
This ultra-fines recovery unit can process up to 450 cubic meters per hour of slurry recovering material as low as 40 microns, thus reducing the volume of solids reporting to storage ponds or water treatment plants. Bringing together a centrifugal pump, a hydrocyclone cluster and a high frequency dewatering screen on one chassis, the FM UltraFines also boasts a uniquely designed conical tank and anti-turbulence system, which is essential in the process of ultra-fines recovery.
Terex WPS, www.terex.com/washing
Van Tongeren System Eliminates Need for Settling Ponds
A green solution for conserving water in aggregate mining and production also solves land use and worker safety troubles. The Gravitational-Inertial Classifier (GIC) system from process equipment manufacturer Van Tongeren America automatically separates dry materials without water to eliminate the need for settling ponds, sludge pits and other basins required to manage the high volumes of wastewater generated daily by the traditional wet process.
A modern, environmentally friendly approach, the GIC opens large areas of land that may be used to increase production and/or store material instead of for managing wastewater.
By removing settling ponds from the site, the GIC also reduces the risk of worker exposure to potentially hazardous materials and eliminates permit-required confined spaces along with the need for dedicated, personal protective equipment while streamlining the permitting process for new plants.
“Real estate is at a premium, so if you don’t use land for settling ponds then you’re essentially creating more land at no cost, just by using the GIC,” said Steve Demeyer, process management manager for Luck Stone, Manakin Sabot, Va.
Ideal for classifying manufactured sand, cement, crushed stone, salt, lime, soda ash and a variety of other aggregates and minerals, the GIC system features a proprietary, heart-shaped design that passes a current of air through a curtain of falling material then directs each particle towards a series of angled vanes.
Coarse particles are discharged and entrained fine particles are recirculated in an eddy current until discharged and captured by a dust collector. The GIC separates particles at any cut point from 300 μm to 63 μm (50 to 230 mesh) in unattended, 24/7 operation.
Van Tongeren America, www.Van-Tongeren.com
Weir Minerals Offers Sand Wash Solution
Weir Minerals announced the Weir Minerals Sand Wash Plant, a complete sand-wash solution drawing on Weir Minerals’ long experience in the sand and aggregate industry.
The Linatex-lined plant produces more saleable product than conventional sand screw plants, with fewer moving parts and an optimised process that produces a drier, higher-quality product with less fines, the company said.
The solution has already proven effective at sites like Coimbatore Minerals in Tamil Nadu, India, where a custom-built Weir Minerals Sand Wash Plant reduced their total cost of ownership by 51%, while offering a 23% reduction in fines that helped their product consistently meet the industry’s high standards for a saleable product.
“We know the most important thing for quarry operators in washing is recovering as much sand as possible to maximize their sales, which is why we’ve designed an integrated solution for washing their product, with a hydrocyclone which can deliver greater recovery than sand screws. In addition, every component has been selected by our expert engineers for its long-service life, interoperability and ease of maintenance,” said Bruce Cooke, global product manager – Sand Wash Plants.
The compact solution features a range of Weir Minerals equipment designed for high efficiency in sand and aggregate applications, including Warman WGR pumps, Cavex hydrocyclones, Enduron dewatering screens, Linatex hoses and Isogate knife gate valves.
The Warman WGR is the pump of choice in the sand extraction industry, combining top of the line hydraulic design with an adjustable impeller, long bearing life and a simplified wet end, making replacement predictable and cost effective.
Precision moulded and lined, Linatex premium rubber is used for wear zones throughout the plant due to its proven wear performance in wet sand applications in operations around the world.
Cavex hydrocyclones provide exceptional classification efficiency thanks to their unique 360-degree laminar spiral, delivering more saleable product than a sand screw solution would.
Enduron dewatering screens reliably separate product with a high degree of efficiency, while robust Isogate knife gate valves contribute to the plant’s straightforward maintenance.
Weir Minerals, www.global.weir
Xylem Drives Digitization Of Water With Smart Pumps
As digital technologies continue to produce powerful value for water managers and the communities they serve, global water technology company Xylem Inc. launched the new Godwin NC100S and CD100S Dri-Prime dewatering pumps, the third and fourth pumps in the Godwin S Series of smart pumps.
Equipped with interchangeable, application-specific impellers and a new generation of cloud-based Field Smart Technology, these new 4-in. surface mounted centrifugal pumps deliver enhanced levels of control and flexibility for the toughest dewatering applications. While each is ideal for the application described below, the pumps enable the operator to switch from a NC100S to a CD100S, and vice versa, due to the interchangeable impellers on both models, thereby providing a ‘two in one’ solution for each pump to increase the application range and removing the need to invest in multiple fleet models.
The Godwin CD100S is ideal for utility and construction applications, as well as emergency response dewatering. The CD impeller, generally used in construction dewatering applications, can be exchanged with a Flygt N-Technology self-cleaning, non-clog impeller, which delivers sustained hydraulic efficiency. This provides customers with the flexibility to tackle stringy, fibrous materials most commonly associated with modern wastewater applications, all with the same pump.
The NC100S and CD100S models feature a redesigned pump-end, resulting in 20% greater pump uptime and 40% reduced service time. Both models also come equipped with a Final Tier 4 (FT4) engine, making them sustainable pump options as diesel particulate emissions are cut by 90%.
Xylem’s Field Smart Technology (FST) comes as standard on all NC100S and CD100S pumps in North America. As Xylem’s first-in-industry cloud-based telematics platform, FST enables the Internet of Things (IoT) across the entire Godwin S series. Using cellular, satellite and GPS technology, customers can track, monitor and control the pump in real-time from any smartphone, tablet or desktop computer. There is also an improved graphical user interface, providing greater choice to the customer when it comes to remote monitoring and control.
All Godwin S-Series pumps come with a Final Tier 4 (FT4) engine to deliver a significant reduction in emissions, supporting a more sustainable operation. The pumps can be fitted with a double-walled skid base to further prevent against costly and environmentally hazardous liquid spills. Electric motors are also available upon request.
Xylem Inc., www.xylem.com
For an outsider, water management might not be the first thing that comes to mind when thinking of quarries. However, water availability and wastewater management have been a strong focus for quarrying and mining operators.
Restrictions on water extraction from the natural environment have made the recycling of process water a must for quarrying operators. Managing process water, reclaim systems, dust suppression and pit dewatering are essential to the success of a sand or aggregates project. By managing these processes efficiently, quarry sites can process more product faster, while lowering their water bill and eliminating the need for double handling.
Most quarries use water in the washing and processing of their products. Sand washing utilizes both recycled and clear water. Once the sand has been processed, wastewater containing product fines and additional wastewater runoff from the stockpiles make their way to storage or tailings dams. All these water sources need to be managed effectively for the quarry to keep their operational costs under control.
“Maintaining the water level balance on site is very important to everyone,” said Darren Van der Westhuizen, territory manager for dewatering at Weir Minerals. “No matter what you’re processing, you’ll always need to move water from point A to point B.”
The new decade has brought to light new problems for fluid transport, from introduction of water restrictions on urban water supplies to climate change affecting the supplies of non-potable groundwater (rainwater, groundwater and stormwater). By transporting and making use of water already available on site, quarries can reduce costs.
“Increased awareness of the positive outcomes achievable with efficient water management provides us the opportunity to partner with customers to explore and develop new and safer water management systems.” said Van der Westhuizen. “We target the challenges the quarries are facing with regards to pumping water around the site with the focus to champion and provide the most optimum solution for each specific and unique application.”
Pumps designed to handle increased suspended solids in water whilst operating at high discharge head pressures could be the answer. With the Warman DWU pump, Weir Minerals provides a pump built to transport surface water from dams and ponds on site back to the washing circuit for recycling. Other on-site water sources, such as tailings dams, might make better use of a pump house or a customized Multiflo barge solution.
“There is more than one way to reclaim water at a quarry,” said Van der Westhuizen. “We engineer our solutions in-house, so no matter the customer’s needs or budget, we can create a custom solution to get the most out of the water they already have on site.”
In 2020, it’s no longer just about moving water around site, now quarries need to work toward closing the loop of water use in their processes. Regulatory and government bodies around the world have begun implementing guidelines for the management of water in quarries. These guidelines promote site water management proposals founded on the principles of waste minimization and active promotion of the reduction, reuse and recycling of wastewater.
Steve Barnett, sand and aggregates sales manager at Weir Minerals, said, “More and more quarries are looking for equipment that will help them to reduce their water usage on site. With the new guidelines, sites are revaluating their water management plans and seeing how an effective plan and change of equipment can contribute to their success.”
The new planning and allocation of water resources covers reducing, reusing, recycling and recovering water wherever possible. Equipment optimized to handle water not only reduces its losses and boosts efficiency, but also frees up water resources that can be used elsewhere in the process for necessary site duties such as dust suppression.
Installing equipment like the Weir Minerals Sand Wash Plant, specifically designed to produce a drier end product, can improve water recovery by up to 35% compared to common sand screw plants.
The conservation of water is a major consideration for a circular economy. As restrictions tighten, quarries are faced with a new question of how to close the loop and get the most from the water available.
“We’re out on-site with our customers every day,” Barnett said. “We see how hard they work, and we know how precious each and every recoverable resource is. Installing a custom engineered solution such as the Weir Minerals Sand Wash Plant doesn’t just provide customers with a drier aggregates product after processing but creates a whole new by-product in ready-to-use recycled water.”
Automated Wastewater Treatment
Mines and quarries must meet EPA and local wastewater requirements for effluent, including those under the Clean Water Act. Under the Clean Water Act, the EPA has identified 65 pollutants and classes of pollutants as “toxic pollutants,” of which 126 specific substances have been designated “priority” toxic pollutants. Failing to do so can result in severe fines that quickly escalate.
Typically, mines and quarries generate wastewater from slurries of rock particles in water that arise when rain washes exposed surfaces and haul roads, in addition to rock washing and grading processes. Wastewater volume can be very high, particularly on large sites. Besides this, extraction of metals such as gold and silver can generate slimes containing very fine particles. In such cases, physical removal of contaminants becomes especially challenging.
For many mines and quarries, this means installing a wastewater treatment system that effectively separate the contaminants from the water so it can be legally discharged into sewer systems or even re-used.
However, traditional wastewater treatment systems can be complex, often requiring smultiple steps, a variety of chemicals and a considerable amount of labor. Even when the process is supposedly automated, too often technicians must still monitor the equipment in person. This usually requires oversight of mixing and separation, adding of chemicals, and other tasks required to keep the process moving. Even then, the water produced can still fall below mandated requirements.
Although paying to have mining wastewater hauled away is also an option, it is extraordinarily expensive. In contrast, it is much more cost effective to treat the industrial wastewater at its source, so treated effluent can go into a sewer and treated sludge passes a Toxicity Characteristics Leaching Procedure (TCLP) test and can be disposed of as non-hazardous waste in a local landfill.
Fortunately, complying with EPA and local wastewater regulation has become much easier with more fully automated, wastewater treatment systems. Such systems not only reliably meet regulatory wastewater requirements, but also significantly reduce the cost of treatment, labor and disposal when the proper Cleartreat separating agents are also used.
In contrast to labor-intensive multiple step processes, automated wastewater treatment can help to streamline production, usually with a one-step process, while lowering costs at industrial facilities.
An automated wastewater treatment system can eliminate the need to monitor equipment in person while complying with EPA and locally mandated requirements. Such automated systems separate suspended solids, emulsified oil and heavy metals, and encapsulate the contaminants, producing an easily de-waterable sludge in minutes, according to mining industry consultants at Sabo Industrial Corp., a New York-based manufacturer, distributor and integrator of industrial waste treatment equipment and solutions, including batch and fully automated systems, Cleartreat separating agents, bag filters and accessories.
The water is typically then separated using a de-watering table or bag filters before it is discharged into sewer systems or further filtered for re-use as process water. Other options for de-watering include using a filter press or rotary drum vacuum. The resulting solids are non-leachable and are considered non-hazardous, so will pass all required testing.
These systems are available as manual batch processors, semi-automatic, automatic and can be designed as a closed loop system for water reuse or provide a legally dischargeable effluent suitable for the sewer system. A new, fully customized system is not always required. In many cases, it can be faster and more cost effective to add to or modify an industrial facility’s current wastewater treatment systems when this is feasible.
However, because every wastewater stream is unique to its industry and application, each wastewater treatment solution must be suited to or specifically tailored to the application.
The first step in evaluating the potential cost savings and effectiveness of a new system is to sample the wastewater to determine its chemical make-up followed by a full review of local water authority requirements, said mining industry consultants at Sabo Industrial.
The volume of wastewater that will be treated is also analyzed, to determine if a batch unit or flow-through system is required. Other considerations include the size restrictions so the system fits within the facility’s available footprint.
Despite all the advances in automating wastewater treatment equipment any such system requires effective separating agents which agglomerate with the solids in the wastewater so the solids can be safely and effectively separated out.
Because of the importance of separating agents for wastewater treatment, Sabo Industrial uses a special type of bentonite clay in a line of wastewater treatment chemicals called ClearTreat. This line of wastewater treatment chemicals is formulated to break oil and water emulsion, provide heavy metals removal, and promote flocculation, agglomeration and suspended solids removal.
Bentonite has a large specific surface area with a net negative charge that makes it a particularly effective adsorbent and ion exchange for wastewater treatment applications to remove heavy metals, organic pollutants, nutrients, etc. As such, bentonite is essential to effectively encapsulate the materials. This can usually be achieved in one-step treatment, which lowers process and disposal costs.
In contrast, polymer-based products do not encapsulate the toxins, so systems that use that type of separating agent are more prone to having waste products leach back out over time or upon further agitation.
Today’s automated systems along with the most effective Cleartreat separating agents can provide mine and quarry operators with an easy, cost-effective alternative so they remain compliant with local ordinances and the EPA. Although there is a cost to these systems, they do not require much attention and can easily be more economical than paying fines or hauling.