Accelerating water remediation from oil sands
Researchers at the University of Alberta, Canada, claim a judicious use of ozone can remediate waste water from tar sands quicker than previous ozonation techniques and natural remediation, which takes 26 years.
Warm water is used to extract the bitumen from the tar sands using surface mining techniques. The waste, including water containing toxic matter, collects in tailings ponds several kilometres wide. Since regulations have banned the use of fresh water for bitumen extraction from tar sands, water from the ponds is recycled for that purpose. Research into techniques to remediate it is ongoing.
Professor Jonathan Martin, an environmental toxicologist leading the research at the University of Alberta, acknowledges that ozonation has been tried in experiments that go back to the 1980s.
Scientists have also tried to add nutrients to the wastewater, but without success.
In one previous study, large amounts of ozone were used to treat toxic substances in the water – mainly naphthenic acids (NA), however, some toxicity remained, explains Martin. He and his colleagues have found that if they only lightly ozonate the water, it would attack the most persistent NA. The scientists also added native microbes from other water samples to do this task. The outcome significantly accelerates the remediation rate.
‘Our study is the first to [look at] microbial biodegradation following ozonation. We experimented with a control (unozonated), 50% NA degradation by ozone and 75% NA degradation by ozone; all three of these were then given the same initial bacteria population. Bioremediation was quickest in the 75% NA degraded treatment’. He adds, ‘The ozone preferentially attacks the more branched NA, which breaks down to form hydroxy- or keto-NAs.’
The unozonated water, he indicates, ‘did not begin to detoxify until more than 60 days after microbes were reintroduced to the water. The 50% NA degraded sample began to detoxify in less than 30 days and the 75% NA degraded sample began to detoxify in less than 14 days’, in laboratory conditions.
However, there remains much work to be done. The researchers want to start field trials and further tests on other aquatic organisms.
‘In this study we’ve seen this technique is less toxic to bacteria. But there is also a need to look at the resulting toxicity to fish and mammals. And the water will eventually get to human communities of course,’ he states.
Remediating the waste water from surface mining of oil sands is only part of the job. As oil is also extracted in situ, clay and other materials also need to be remediated.
The University of Alberta’s research on this project was funded by Syncrude, an oil sands extraction company working on the Athabasca Oil Sands Deposit in North Eastern Alberta, Canada.