Underground UV Water Treatment and Recycling System Gives New Life to Used Water at Musselwhite
By Liza Wade, VP Environment
Goldcorp is on an exciting journey Towards Zero Water. Every journey begins with a deep breath, and gathers momentum by diligently putting one foot in front of the other. Sometimes you discover you’ve already headed on your way without consciously knowing it. There are downhills to coast, uphill parts that require perseverance, and no important journey is complete without some obstacles along the way. Surmounting obstacles in creative ways with your colleagues is what makes the work fun!
The early parts of our journey Towards Zero Water have led us to some important discoveries:
- Did you know that Goldcorp manages more water than ore by mass?
- This makes us a water management company as well as a mining company.
In 2016, each of our currently operating mines moved from 2 to 17 times more water than ore (by mass), depending on the mine site circumstances. Water cannot be moved, pumped or stored without spending money - on people, materials, equipment, and power. So, we intuitively know that by saving water, we are supporting our overall business objectives at Goldcorp.
Some water savings projects at Goldcorp have already shown successes, some have recently been deployed, and many more are being considered for the future. Here’s one from our Musselwhite Mine
Situated immediately below Lake Opapimiskan at a depth of more than 1,000 metres, the Musselwhite mine has always had easy access to water for its mining operations. But the Ontario mine has been using considerably less water from the lake over the last six months thanks to a water recycling system that has been installed within the underground mine itself, which could ultimately eliminate the need for fresh water consumption from the lake altogether and help Goldcorp achieve its Towards Zero Water vision.
Since gold production started at Musselwhite in 1997, the mine has historically used 1,300 cubic metres of fresh water on a daily basis, drawn from the lake for the purposes of development drilling, long-hole drilling and dust suppression.
In 2011, when a new pump station was being planned for Musselwhite’s 770 metre level (mL), Colin Pickett, Underground Mine Manager, and his team started looking for sustainable options to reduce the mine’s environmental footprint. “We were primarily driven by the need to reduce energy use at the mine from electric motors used to pump water to and from surface,” recalled Pickett. “We felt the best option to reduce energy consumption and optimize water use was to treat and recycle water that could be reused in underground operations.”
Pickett and his team reviewed various options available, working with Kozar Engineering in Thunder Bay to select and customize an ultraviolet (UV) water treatment system to serve as a key component of an underground water recycling plant.
Unlike chemical approaches to water disinfection, UV disinfection provides rapid inactivation of potentially harmful microbes through a physical process. When bacteria, viruses and protozoa are exposed to UV light at a 254 nanometre wavelength, their DNA is destroyed, which prevents dangerous viruses such as cryptosporidium and e-coli from reproducing and causing harm. There are also no residual chemical or hazardous by-products at the end of the process compared to chemical treatment options.
Ongoing communications proved integral to the successful implementation of the water recycling project at Musselwhite. Local First Nations were consulted and regular meetings were held with key personnel from all mining departments to review and discuss the development and construction of the 770 meter level water recycling plant. “Maintaining transparency with the workforce throughout the water recycling plant’s development was critical to making this project a success,” stated Shane Matson, Sustainability Manager at Musselwhite. “Everyone knew what their responsibilities were and really embraced the vision of this project in support of Towards Zero Water.”
Following the plant’s construction in the spring of 2016, the water recycling system underwent rigorous testing to ensure it met stringent performance, environmental and safety standards. “We embarked on a five-month testing process before we even fired up the system,” recalled Pickett. “We needed to make sure the recycled water was clean enough that it could be used again without any impacts on our workforce or equipment.”
The water recycling project, which was commissioned in November 2016, is a weir sump filtration system in which two 400 horsepower pumps draw used water into three 136,000 litre (30,000 gallons) holding tanks at the 770 meter level of the mine. From there, the water passes through a strainer and the UV treatment system to remove impurities before being pumped to lower levels of the mine to be used again. Recycled water is gravity fed to lower levels and circulated throughout the mine by 15 horsepower pumps.
“Once the system was up and running, there was an immediate reduction in fresh water consumption from the lake,” pointed out Doris Achircano Condori, Environmental Engineer at Musselwhite, who is the mine’s Water Stewardship Champion. “The other benefit was the reduction in electric power use. We don’t need to pump water to surface anymore. Rather, we can recycle it right there in the underground, which has resulted in significant energy and cost savings.”
Since the water recycling plant was installed, Musselwhite has reduced its daily water consumption from the lake by almost 40 percent to 800 m3/day. Eliminating the need to pump dewatering water to and from surface has significantly cut back pump station working hours, which is estimated to save the mine approximately $153,000 annually in energy costs. The new system also helped reduce the need for on-site diesel power generation due to lower total energy demand. Additional savings were realized from lower maintenance requirements for the underground sump and the existing dewatering system.
Given the tangible environmental and economic benefits realized, there’s been considerable interest from other Goldcorp operations in the UV water treatment and recycling project. “We hope what we learn from this project will transfer throughout the organization for other sites to take hold of and make their own,” noted Matson.
Musselwhite is now in the process of installing a second water recycling plant at the 220 metre level, which will be completed in 2018.
“This plant will give us the ability to capture and reuse all our recovered water, leaving us with much less water to pump to surface,” stated Achircano Condori. “Once the 220 metre level system is operational, it should bring Musselwhite down to almost zero water intake from the lake.”
“The UV water recycling project has been a great initiative,” concluded Pickett. “It’s enabled the Musselwhite mine to operate more cost efficiently and minimize our water footprint by reducing fresh water taken from the lake. It’s also been a great example of people coming together to realize our company-wide goal of Towards Zero Water.”
For further information on Goldcorp’s commitment to sustainability, visit the 2016 Sustainability Report