For mining operations, effective water treatment is about more than meeting regulatory requirements and maintaining a social license to operate. Choosing the right approach to water treatment can have a profound impact on a mine business. One increasingly attractive option for mining companies is the deployment of mobile water treatment technologies.
Mobile water treatment technologies are pre-packaged on a trailer, skid or container allowing both highly mobile treatment and rapid deployment. Mobile assets are typically pre-engineered with ‘plug-and-play’ connections, making transport to even remote sites relatively straightforward and allowing ease of installation.
Veolia’s Mobile Water Services, for example, offer an alternative to fixed plants for a wide range of mining and other industrial applications with flow rates of anything from 1 cubic metre/hour to 500 cubic metres/hour. Available as standardized modular systems, higher flow rates are easily achieved by adding further units.
Often considered as a temporary or emergency solution where an existing plant has failed, mobile assets are also ideally suited to use during planned commissioning, refurbishment or maintenance projects and even for longer-term water treatment requirements, such as during decommissioning and site remediation.
A wide range of treatment options are available, too. Processes including clarification, filtration, deionization, demineralization/softening and metals removal are all possible from a mobile platform. For the mining sector, removal of metals and other materials that are toxic to aquatic life down to parts per billion levels are typically required as part of the regulatory process.
Cutting capital costs
For the junior mining sector in particular, one of the perennial challenges is the provision of capital. The nature of such a business means that when raising capital in the marketplace there is a strong focus on securing funding for revenue-generating equipment used in ore processing within the mill. With the focus of major capital purchases centered on the mill, capital expenditure for water treatment is more challenging.
Mobile water treatment makes an attractive solution as it can be more easily financed through the operational expenditure budget on a month-by-month basis during the construction and development phases. Once operations are successfully generating income, investment in permanent water treatment facilities is more manageable.
Another one of the key benefits associated with mobile water treatment is found in the regulatory approvals process. Mobile water treatment assets can provide important baseline data to support accelerated permitting. Operators are able to execute both mobile and permanent assets in parallel and by getting assets in place, it allows them to prove that the process is effective while mining operations are underway.
Regulatory requirements related to mine water discharge are also becoming far more stringent in Canada and elsewhere. Tougher requirements for maximum total suspended solids (TSS), pH balance or the need to remove certain constituents such as ammonia, arsenic or other heavy metals means that water treatment technologies have also had to evolve and develop. As increasingly hard-to-treat wastewater demands have emerged, mobile technologies allow operators to establish and understand the process and the specific challenges associated with each application. This in turn supports the development of permanent onsite water treatment facilities.
The capabilities of the mobile plug-and-play solution offers other potential benefits, too. For example, there is a role for mobile equipment at existing operational sites where conditions or requirements may potentially vary over time. Changes to a mine water balance can occur, there may be seasonal variations such as spring melt or where a tailings compound reaches a level where there is a risk of a breach.
Earlier this year, for instance, a Vancouver-based mining company selected Veolia mobile technologies for a new wastewater treatment plant in order to meet strict regulations for discharges to the environment in Ontario’s Red Lake Mining district. Mobile assets for metals removal supplemented a permanent AnoxKaldnes (Veolia’s trademarked technology) moving bed biofilm reactor (MBBR) system for toxicity removal.
Supplementing an existing system with mobile assets can also help draw down tailings water levels to give more free board in an impoundment area. As a result, mobile temporary solutions may also yield previously inaccessible resources. For example, dewatering a large pit may take several years. By installing high-volume temporary equipment, this process can be significantly accelerated.
The modular system also gives more scope to quickly scale treatment capacity as required in response to market changes. A wastewater treatment facility installed and based on an anticipated range of production scenarios could be insufficient if production at a site is significantly increased in response to changing commodity prices, for example.
Mobile assets are able to supplement an existing system and help take up extra capacity as needed. It also gives operators the opportunity to assess the specific circumstances and determine the requirements or necessity for a long-term solution depending on their strategy. This approach is also a reflection of the often volatile nature of commodities markets. Particular mining developments may only have a lifespan of a decade or less, making permanent water treatment assets an unwieldy investment.
The mobile solution may also suffice where a permanent plant may be considered a stranded investment at a mine which is in the process of being decommissioned. This also applies to the need for remediation at closed mine sites or elsewhere.
For example, a derailment that led to an ore spillage at a site in northern Ontario saw metals begin to leach into the groundwater. However, this site was not only environmentally sensitive but also presented a significant challenge for access with only the narrow and congested railbed space available.
Removal of TSS and metals such as copper, zinc and others saw the deployment of a complete turn-key mobile treatment system for several years. Featuring Actiflo units from Veolia for TSS removal as well as Hydrotech Discfilters for polishing with a flow rate of 5455 cubic metres/day, the Actiflo High-Rate Clarifier has a footprint up to 20 times smaller than conventional systems.
Remote access and speed of deployment
One of the characteristics of mine sites is that they are frequently located in remote, hard to access areas. The physical challenges of such locations make developing permanent assets difficult and time consuming. Mobile assets are more easily transported to even the most remote locations and in the Canadian North and elsewhere, a relatively narrow weather window makes these capabilities advantageous.
Able to treat large volumes of water with unique technologies that offer a small footprint is another big driver for mobile assets. For example, Pretium Resources awarded Veolia Water Technologies a contract for the Brucejack gold mine located northern British Columbia. Initially deployed to dewater the mine during the exploration phase, Pretium chose the mobile Actiflo system in response to the remote location 275 km northwest of Smithers. The mine can only be reached via a 12-km glacier.
Minimizing TSS and heavy metals from their gold mine effluent while using as little land as possible, the system allowed construction operations to be developed during the almost two years needed to obtain all necessary environmental federal and provincial regulatory permits.
Discrete containerized units mean that different modules can be up and running in a relatively short period. A mobile treatment plant can be mobilized and operational in just weeks, whereas construction of permanent infrastructure typically requires a minimum of a year and in many cases much longer than that.
Making mobile water treatment the solution of choice
In response to changing demands from regulators and operators, mobile water treatment technologies are also evolving. With physical and chemical separation for suspended solids, turbidity, hardness and metals removal, membrane separation and demineralization for total dissolved solids, specialty ion exchange and heavy metals removal, there are a host of existing mobile technologies available and new ones are emerging too.
Certainly, effective water treatment is critical to mining operations and without it an extractive business can generate no revenue. But considering the business case for mobile water treatment assets, is it clear that there is far more scope than emergency short-term deployment.
Indeed, mobile treatment is going from the crisis option to instead becoming the solution of choice from the start. With flexibility, speed of deployment and cutting-edge technologies, mobile treatment is a key part of the mining portfolio during exploration, development, operational and decommissioning phases of mine life.
Originally published in Canadian Mining Journal, January 2021