Nature knows best - biofilms for tailings detoxification

Materials World magazine
5 Feb 2012
technician in lab with flask of liquid

With a constantly shifting global energy landscape and the increasing importance of the Alberta oil sands in Canada, the safe disposal of tailings has become a crucial issue.

A team from the University of Alberta, based in Edmonton, Canada has developed biofilms capable of breaking down the toxic matter found in tailings ponds.

The method is a similar one to that found on remediation landfarms, which harness nature’s capacity to break down matter, and is tailored to deal with the extreme environment of tailings ponds filled with toxins and metals.

‘Wherever there is energy, life forms are going to use it,’ says Dr Howard Ceri, a microbiologist at Alberta who co-leads the project. ‘Ever since the oil sands formed, bacteria have been evolving that can extract energy from them.’ The team found bacteria that were indigenous to the oil sands – known as biofilms – have evolved to be highly tolerant to the stresses of the tailings water. However, as this occurs over millions of years, Ceri and his team investigated ways to expedite the process.

According to Ceri, ‘if we can organise these bacteria, then we can more efficiently handle the breakdown of complex organics without having the build up of toxic intermediates.’

To make the biofilms, they carried out a two-fold process. Firstly, they identified exactly which organisms they needed, then built the bioreactors to produce them. After taking a sample from a tailings pond, Ceri’s team found that by altering the growth conditions and exposing the biofilms to different stressors, they could customise the metabolic characteristics of the biofilms to get the desired breakdown effect.

The next step involved growing the biofilms on support materials to test in bioreactors. The research led to a spin-out company centred on the team’s high throughput bio-screening system. ‘We are able to work in small volumes but with huge numbers of possibilities, it’s just a matter of scaling that up.’

Ceri acknowledged that the process wasn’t so much a question of innovation, but about taking an existing technology and applying it to a particular problem. He adds that this sort of bespoke bioengineering could help steer people away from methods that disrupt eco-systems, such as the introduction of foreign entities – for example animals or superbugs – into environments where they don’t belong.

Instead, once the biofilms complete their role of remediation, as they have evolved to feed off the specialised compounds of the tailings ponds, Ceri claims they will simply revert back to their normal concentrations. ‘They are already there – that’s where we got them from, we didn’t add anything or alter it in any way, we’re just giving an operational organisation to that environment so it becomes more efficient.’

If successful, the research could ‘close the loop’ of the oil sands operations.

Ceri even adds that the metals within the oil sands could be extracted and sold for profit. However, Dominic Thomas, a Drilling Advisor at EXCO Resources, based in Dallas, USA, pointed out that ‘The concept of using nature to “process” oily residues is an established process. However, stimulating indigenous bacteria to work in the climate of Alberta may be an advance. It’s not ideal to wait many months to achieve cleanliness, but I did not pick up any reference to rate. The other point of interest is the implication that these bacteria can remove metal contaminants. It would be interesting to learn how this is possible, and what happens to the metals.’