Simplifying arsenic sludge management at a gold mine
Mining | DATE POSTED: August 19, 2021
Arsenic-laden groundwater continually infiltrates the shafts of a gold mine in Western Canada. As it’s pumped out, an onsite treatment system removes the arsenic to produce effluent that can be safely released. But the system also produces large volumes of sludge—about 1,900 litres every 45 minutes. The sludge was a challenge for the site’s existing media filtration system and a faster, more reliable and more cost-effective solution was needed. Learn how the Bishop Solids Management Solution provided a simple, low-energy solution that achieves dewatering, filtration and containment in a single step.
Ammonia discharge limits are tightening up for Canadian mines. Be ready with a BioCord system
Mining | DATE POSTED: January 27, 2021
By June 1, 2021 metal and diamond mines in Canada will need to comply with a new lower discharge limit for unionized ammonia. Over 100 mines will be affected by this revision to the Metal and Diamond Mining Effluent Regulations (MDMER), which sets a federal effluent limit of 0.5 mg NH3/L.
To achieve this new regulation, changes may be needed to a mine site’s wastewater treatment system. But the new ammonia target can likely be reached without the need for complex or costly technology upgrades. Many mine sites use simple lagoon systems for wastewater treatment—in part due to their ease of use and low operating costs—and there are upgrade options that can maintain this simplicity and affordability while also improving ammonia removal.
More nitrifying bacteria = better total ammonia removal
A simple, fixed-film biological treatment system such as Bishop BioCord™ Reactors can dramatically improve total ammonia removal, without significant changes to the way a lagoon is operated. That’s because a BioCord system is designed to enhance the existing lagoon process rather than add another step or sidestream process to the plant.
Unlike moving-bed or submerged-bed biofilm systems, which require additional tanks or cells, BioCord Reactors can be installed directly into the treatment lagoon to provide a massive surface area on which preferred, naturally occurring bacteria can grow. It’s like a condominium for bacteria; made from densely arranged loops of polymer fibers that are suspended from free-standing frames. This enables BioCord to establish a robust population of nitrifying bacteria that is many times greater than what can be maintained in an ordinary activated sludge lagoon.
BioCord isn’t limited to upgrades only. This modular system can also form the foundation for new wastewater treatment plants that are designed as lagoons, tanks or even temporary containers.
High oxygen transfer is critical
Each frame is also equipped with a micro-bubble aeration system powered by a low-energy compressor. This design enables the system to achieve high oxygen transfer to the biofilm for a fraction of the capital and operating costs of a typical blower-powered lagoon aeration system. Oxygen is a critical, and often limiting, parameter for nitrifying bacteria to proliferate, so having high oxygen transfer at a low energy cost is a tremendous advantage.
Once operational, a BioCord system acclimatizes and adapts to the range of pH, temperature and contaminants that it may experience in the mine’s wastewater lagoon, including high levels of ammonia, nitrogen and cyanide.
BioCord testing shows that the system can achieve over 99% ammonia reduction in synthetic wastewater concentrations as high as 750 mg/L. Since the system is modular, the system can be sized to meet the required ammonia target and quickly expanded if conditions change.
Learn more about the Metal and Diamond Mining Effluent Regulations.
Learn more about BioCord Reactors for high strength wastewater treatment.
Contact us to discuss your high strength wastewater treatment needs.
How to simplify sludge management for acid mine drainage (AMD) treatment
Mining | DATE POSTED: March 26, 2019
Treatment of acid mine drainage (AMD) produces large amounts of sludge that poses serious challenges for storage, dewatering, disposal or reuse. A Bishop Solids Management Solution, with Geotube® containers, provides a new approach that outperforms mechanical dewatering processes, such as belt presses, and even contributes to reliable containment of metal precipitate and dewatered sludge.
With the Bishop Solids Management Solution, sludge can be pumped directly from the AMD clarifier to a Geotube® dewatering container. As the sludge is pumped, the Bishop VEPAS polymer system adds a specially selected coagulant directly to the feed line, eliminating the need for mixing tanks and immediately starting the coagulation and dewatering processes.
The simple, low-energy process can be automatically controlled through the plant SCADA system, achieves excellent dewatering and produces high-quality filtrate. Geotube® containers have been proven to achieve excellent dewatering of AMD sludge, typically achieving nearly 30% solids within about 72 hours. Belt presses, on the other hand, can only achieve about 10% solids, consume far more energy and require significantly more maintenance.
The Omega Mine in West Virginia has been using Geotube® containers for several years to dewater sludge produced by an AMD treatment plant. The plant receives raw water at a rate of about 200 GMP (46 m3/hr) and uses lime to raise pH from about 2.5 to 7.0. Chemicals are also used to capture heavy metals and reduce the concentration from about 1,985 ppm to less than 3.73 ppm. Treated effluent from the plant and the Geotube® dewatered sludge is discharged to the local receiving body.
Once dewatering is complete, Geotube® containers can remain on site in the lined lay-down area and multiple layers of containers can be stacked on top of one another. The plant is currently participating in an innovative research study to reclaim rare earth metals from the dewatered sludge. Researchers believe the sludge contains high concentrations of rare earth elements, which when harvested, could be worth more than $800,000 per year. We’ll tell you more about this story in a future issue of the Bishop Water e-newsletter.
Watch this video to learn more about Geotube®
containers for mining and mineral processing.
Learn more about the Bishop Solids Management Solution
Contact us to discuss your dewatering needs.