Bioremediation is an extremely beneficial option for remediation, often offering extensive environmental and financial advantages over traditional remediation methods. But it is not without its complications.
Site conditions need to meet certain specifications to ensure success (sometimes these can be manipulated, sometimes not), and the science behind bioremediation is highly technical. It’s not just a matter of buying a solution (a culture) that promises to fix your problem (contamination).
This came to attention recently when we were asked for a culture to bioremediate Carbon Tetrachloride (CTC). This culture doesn’t exist – there are no known bacteria that can metabolise CTC. But that doesn’t necessarily mean you can’t exploit biological activity to degrade it.
The hefty scientific and technical intricacies and misinformation about the scope of capabilities can stop some people from pursuing bioremediation. But it shouldn’t.
To highlight the full potential of bioremediation, its capabilities and how it can work in a wide variety of situations, we’ll use the recent experience of the bioremediation of CTC to demonstrate.
The challenges of Carbon Tetrachloride
A site contaminated with Carbon Tetrachloride (CTC) was looking for a way to safely perform groundwater remediation. But that’s no easy ask.
Carbon Tetrachloride (CTC) is a highly toxic compound, once used as a chemical solvent, and also widely as a refrigerant. A cause of cancer, acute toxicity and organ failure, it’s no wonder it’s listed in the US EPA top 50 pollutants. While no longer used, CTC still exists in our environment. Government regulations state that CTC must be kept below certain levels to be considered safe, so viable methods to remove it from sites are in demand.
It’s unsurprising that those affected by CTC would look to bioremediation for a possible solution, as the compound can be eliminated without physical removal that risks further contamination.
However, no bacteria have been found that can break down CTC in normal groundwater conditions. Organochlorine respiring bacteria (ORB) would usually be used, yet no strain that can metabolise CTC has been found.
Hence, when people go looking for a culture to help rid them of CTC, they will fail to find one – it does not exist. But, with the right bioremediation expertise and knowledge, CTC can indeed be broken down naturally.
How do you bioremediate a compound that can’t be metabolised?
While ORB is unable to metabolise CTC in its natural form, there is a way to work around this using a compound that is already omnipresent in groundwater – sulphate.
Sulphate alone will not react with CTC. However, sulphate reducing bacteria (SRB) respires sulphate, turning it into sulphide. By introducing SRB into CTC contaminated groundwater, it will turn sulphate into sulphide, which then reacts chemically with CTC to turn it into the organochlorine daughter product chloroform (CF).
In its new form, CF can be metabolised by ORB, removing it from the groundwater. Novorem supplies a Dehalobacter based chloroform degrading bioaugmentation culture isolated by Professor Mike Manefield’s research team at the University of NSW.
By lowering the redox potential (ORP) of the groundwater and feeding the SRB with a slow-release electron donor, you can remove CTC. This in turn relieves inhibition CTC imposes on microbial activity in the subsurface environment, enabling ORB to clean up not only chloroform but co-contaminants such as perchloroethene or 1,2-dichloroethane.
Removing CTC is not only important to meet legal obligations, but will improve the overall condition of your groundwater. Now that removal can be achieved through bioremediation, there are further benefits available to your operation. The minimal disruption to the site means a quicker, cleaner and more manageable remediation process that also minimises cross-contamination risks and reduces costs. As our community seeks more sustainable remediation options, our technologies rise to the challenge.
CTC is not commonly present in groundwater and is generally only a problem for chemical manufacturing sites. However, this example stands to demonstrate the wider capabilities of bioremediation, and the scientific expertise behind it.
Remediation is not always about one contaminant. There are flow on effects that have to be considered, as demonstrated with the inactivity of ORB in the presence of CTC.
Bioremediation isn’t always possible, but shouldn’t immediately be dismissed as an option before engaging experts. Especially considering bioremediation offers considerable cost savings and minimised disruption and risk of further contamination to surrounding environments when compared to traditional remediation techniques.
If you are interested in further exploring bioremediation, or would like more information about Novorem’s expertise and capabilities, click here to contact Novorem.
Author Bio:
Önder Kimyon is the principal scientist of Novorem Pty Ltd and is a renowned expert in environmental science and microbiology.
Önder and the Novorem Team have made award-winning contributions to environmental research and biotechnology development, including the biological degradation of contaminants of concern.
If you would like to know more about microbiology or bioremediation, click here to contact Önder.
References:
Koenig JC, Lee MJ, Manefield M (2012) Successful microcosm demonstration of a strategy for biodegradation of a mixture of carbon tetrachloride and perchloroethene harnessing sulfate reducing and dehalorespiring bacteria. J Hazard Mater 220, 169-175.
Matthew Lee, Adrian Low, Olivier Zemb, Joanna Koenig, Astrid Michaelsen and Mike Manefield (2012) Complete chloroform dechlorination by organochlorine respiration and fermentation. Environmental Microbiology. 14, 883-894.