Many mining operations rely on tailings dams for their tailings management. However, when these dams fail, it can result in significant harm to people and the environment. Now, with regulatory pressure on the rise, the mining industry needs to find better alternatives to tailings dams – like high-pressure filters – in order to ensure safe and efficient operations.
Recent events like that at the Brumadinho dam in 2019, where hundreds of people died and 12 million cubic meters of iron waste were released into the environment, cause concern for the long-term use of tailings dams.
While incidents like these don’t happen every day, the potential for damage is high if an accident does occur. Tailings dams can fail for any number of reasons, including:
Tailings are a common byproduct of mining operations. To create a concentrated mineral product, most mined ore – from gold to iron – must be crushed, ground, and mixed with water, creating a slurry of silt and gravel, i.e. “tailings.” The valuable metals are then removed from this mixture, leaving behind a slurry of fine mineral particles and water. These tailings are not insignificant. For example, for every ton of hard coal produced from mining operations, an average of ½ ton of waste remains.
The problem with tailings is that they can be unstable and integrating them into the natural mineral basin can be difficult. When the leftover metals or minerals present in tailings are exposed to air, they can produce acids and cause acid drainage. These slurries have to be treated to prevent local water supply contamination for both surface and groundwater.
This all means that proper tailings management is critical to the continued success of the mining industry.
For many mining operations, the go-to method of managing tailings is to use a tailings facility or dam. The problem here is that if these dams fail, they can cause significant harm to people and the environment, putting a hard stop on mining operations and causing businesses to incur major penalties.
Even though tailings dams do not fail very often, they fail at a higher rate than most other types of dams. According to Science Magazine, during the past century tailings dams have failed at a rate of more than 100 times that of reservoir and power dams.
Upstream dams, which are built in step-like stages, are historically the most prone to failure.
One of the most common and cheapest designs, upstream dams save money since the tailings essentially serve as construction materials, with each new “step” built partially on a foundation of tailings. However, tailings are unpredictable building materials. They can easily become waterlogged, reducing the friction that binds the dam together. Poor drainage and construction flaws can make this problem even worse, causing entire sections of the dam to liquefy in the most extreme cases.
While constructing better and more custom dams is one approach, it does not solve the root issue. With the number of tailings in these dams growing larger by the day, can the industry really afford another failure?
In an effort to reduce the need for tailings dams and work toward better, safer and more sustainable tailings management, wastewater treatment and mechanical filtration is necessary. Here are a few different options available today:
Hydrocyclones
Effective at removing large amounts of solids without the need for added chemicals, hydrocyclones are a cost-efficient way to streamline your wastewater. Using centrifugal forces as their means of solids removal, hydrocyclones are relatively inexpensive, can process large volumes of water and are relatively simple to maintain.
Whether you are using a pond or a filter press, hydrocyclones can help remove a large amount of solids and aggregate prior to your primary method of wastewater treatment. Their main downside is that they cannot remove all particle sizes, meaning that you will need to employ another method of wastewater treatment as well for total solids removal.
Belt Filters
Companies looking to find an option with a smaller footprint that does not require a lot of initial capital will sometimes turn to belt filters. Here, the wastewater slurry is dewatered between two moving belts under tension, running over and under several rollers.
However, similarly to centrifuges, operating costs are rather high as a significantly high dose of chemical flocculants is required to maintain operations. Belt wear can also happen rather quickly, requiring significant downtime and maintenance. It should be noted that the filtered cakes produced by the belt press are “spadable” and may need further processing before dry stacking.
Filter Presses
As one of the oldest and most trusted pieces of dewatering equipment, filter presses are effective at solids removal. In a filter press, slurries are pumped in using a feeding pump, then pushed through chambers made out of filter plates.
Both low- and high-pressure filter presses are available for mining applications. Generally, high-pressure filtration is better, as low-pressure filter presses aren’t as efficient and require more complex designs to get the job done.
High-pressure Matec® filter presses available from ChemREADY represent a huge turning point in the water treatment market, offering better tailings management than ever before. These highly engineered filter presses use pressures of 16 to 21 bar to handle even the most difficult and hard to treat slurries.
Matec filter presses use significantly fewer chemical flocculants than other water treatment equipment and require less maintenance and upkeep to work properly. They also produce highly stable and stackable cakes for easy tailings discharge. Compared to other filter presses, Matec filter presses offer:
Here at ChemREADY, our team of experts can help you achieve better tailings management. By conducting a thorough analysis of your mining wastewater, we can help you find the perfect combination of chemicals and mechanical filtration means for your unique operation.
Typically, after using our specially formulated chemicals to treat wastewater to the perfect state for solids removal, we deploy a range of solutions from ultrafines recovery to water clarification. Then, with a large amount of the solids already separated, a filter press can finish off the dewatering process.
ChemREADY’s combination of chemical and mechanical solutions means one thing for your business – better mining wastewater treatment. Our unique solutions allow you to better manage your slurry or tailings ponds, or even eliminate them altogether.
