In-situ groundwater remediation

By Jake Gossen

3 min read

Many of our industries, for example agriculture, depend on groundwater. Amid the rapid growth of human activity and industrial development, groundwater quality in certain areas, has decreased due to contamination of waste material and by-products.

How do we fix contaminated groundwater?

Groundwater remediation is a critical process that treats polluted groundwater by either removing the pollutant or converting it into a benign product. Remediation techniques include biological, chemical and physical treatment of the contaminated water. During remediation, it is critical that new contaminants are not introduced as part of the process.

Remediation in action

A recent project in Alberta involved the remediation of a groundwater copper plume that threatened nearby aquatic life in a freshwater river. The challenge for our team of environmental scientists was to design, test and then execute an in-situ groundwater remediation program that did not involve excavation at site.

Lab work – designing the solution

We first developed a conceptual site model to understand the extent, flow and attenuation mechanisms of the copper plume in groundwater. We then identified a potential solution to treat the contaminated groundwater by using the properties of ‘rust’ (i.e., hydrous ferric oxide (HFO)) metals naturally present in many aquifers. In particular, the ability of HFO to bind with dissolved copper, turning it into an insoluble solid.

By collecting groundwater and soil from the site and through various bench-scale column tests, we determined the optimal concentration of HFO needed to remove the dissolved copper from the groundwater plume and bind it onto HFO surfaces (i.e., remediate the copper by converting it into a less bioavailable product).

In-situ pilot work – testing the solution

Taking our results from the lab to the field, we conducted a pilot scale test on-site, where we installed HFO injection and monitoring wells for real-time evaluation of groundwater quality. The study showed that HFO was effective at remediating dissolved copper at lower concentrations than determined in our bench scale tests and that results achieved in the lab could be replicated with some adjustments in the field. Post-remediation verification sampling has indicated that following an initial decrease in dissolved copper, concentrations continued to slowly decrease over time.

Lessons learned helped us develop a full-scale remedial design. By taking the above steps of first conducting lab work and pilot testing, the final design and solution were achieved with cost savings for our client.

The remediation process – implementing the solution

The full-scale remediation solution included the installation of customized wells at three strategic areas at the site. We determined “six-packs” were the optimal well configuration for remedial HFO injections - three wells for injection and three for extraction. Additional wells installed down-gradient of each six-pack were outfitted with a water quality monitoring sonde with blue-tooth capability. This enabled the data to be closely monitored in real time from any location and informed us as to whether dosing adjustments needed to be made. These down-gradient wells were also used to collect baseline and post-remediation groundwater samples to evaluate performance of the remedial injections outside of “injection” zones.

Applying this approach to other contaminated groundwater sites

The remediation technology and steps described above can be tailored to different site conditions and metal contaminants. By first conducting lab work, then testing the solution as a pilot study, we were able to take lessons-learned, implement them, and then undertake a full-scale remediation successfully and efficiently. This process is cost and time efficient.

We make the process sound simple here, but a successful in-situ groundwater remediation takes expertise and years of experience. Hemmera, a wholly owned Ausenco company, has extensive experience in groundwater remediation across Canada. Our team of respected environmental experts and technical specialists provide customized assessments and solutions for each site and are here to help.

Contact Jake Gossen with any questions and let us help you today.