Bacteria may be small, but they do heavy lifting in remediation and extraction
A few key microbes are on the verge of becoming key players in B.C.’s mining industry. Engineering professor Sue Baldwin has spent much of the past 15 years farming various combinations of anaerobic bacteria that have the ability to consume or remove heavy metals from mine tailings.
Tailings are ground up rock and chemical pollutants left over from the extraction of metals from ore. Baldwin has her toes in the water of several important cleanup projects, including the Teck Resources smelter near Trail, the Imperial Metals Mount Polley Mine, and analysis of the selenium-contaminated run-off from coal mine waste in the Elk Valley.
Imperial Metals has been operating a 450-litre-a-minute anaerobic biological reactor at Mount Polley since 2009, according to project engineer Luke Moger. The researchers are working to find the optimal environment and combination of microbes in which sulphate-reducing bacteria mitigate acid mine drainage and metal pollution by consuming sulfates in the tailings pond and water that has come in contact with waste rock. This creates sulphides that react with metals in the water to form harmless solids.
The project, now in its second three-year phase, is a partnership between Imperial Metals, Baldwin’s lab at the University of B.C., and Genome BC, which directs funding to research on the application of genomics in sectors such as health care, forestry and mining, including some of Baldwin’s work.
Genomics — the analysis of the complete genetic blueprint of living things — makes it possible to identify individual bacteria or combinations of bacteria that have desirable characteristics, such as the ability to remove metals held in solution.
The problem has been figuring out how to get bacteria to do this on an industrial scale and do it consistently, according to Baldwin.
“Over time, the microbial community in these bioreactors can shift from a favourable group of microbes to different microbes that do not contribute to treatment effectiveness or may have undesirable consequences,” said Baldwin in an email interview. “As we design and operate these bioreactors, we can use genomics to track the microbial community and use this information, together with other geochemical and physical information, to diagnose problems and adjust the operating conditions if needed.”
Seepage water from smelter waste at Trail contained a complex mix of arsenic, zinc, sulphate and other trace metals, but the bioreactor was successful at removing the contaminants and rendered the water harmless to aquatic life, she said.
Teck has a multi-faceted water quality research program and several studies on the use biological processes to maintain water quality have shown promise, said spokesman Chris Stannell.
“Bacterial action has long been known to work in these sorts of roles, the trick is to get it into a scalable form,” said Steve Robertson, vice-president of corporate affairs for Imperial. “They work very slowly for the volume of water that we are dealing with, so the challenge is to make the bacteria as productive as possible.”
The payoff for creating a passive, self-sustaining biological system to purify water contaminated by extraction and processing is quite substantial. Mitigation and remediation require significant capital investment and operating funds, Robertson said. Water treatment may be required for decades after a mine closes, powered and manned at the company’s expense.
Snapshot of a system
Judy Isaac-Renton and Patrick Tang of the BC Centre for Disease Control are developing tools that will take genetic snapshots of thousands of bacteria, viruses and protozoa in both healthy and compromised watersheds in B.C.
Their project, supported by Genome Canada and Genome BC, essentially takes all the creatures in a water sample, blends them together and analyses the trillions of pieces of genetic information — the meta-genome — looking for the signals that are representative of a healthy ecological system or indications of disruption due to pollution.
“We look for genetic signatures for certain organisms and for signatures that are indicative of certain micro-organism function,” said Tang.
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