Bioremediation
What is Bioremediation?
Bioremediation uses living organisms to clean up contaminated soil or water. Despite its broad definition, bioremediation usually refers specifically to the use of microorganisms. Bioremediation is a combination of two words – bio, short for biological, and remediation, which means to remedy. The use of plants to clean up the environment, known as phytoremediation, is also considered a type of bioremediation, and is covered as a separate topic on this Web site.
Learn more about Phytoremediation
The main types of bioremediation are as follows:
All three types of bioremediation can be used at the site of contamination (in situ) or on contamination removed from the original site (ex situ). In the case of contaminated soil, sediments, and sludges, it can involve land tilling in order to make the nutrients and oxygen more available to the microorganisms.
Bioremediation depends on the natural biological processes of microorganisms, one of which is metabolism.
Microbial Metabolism
Metabolism refers to all the chemical reactions that happen in a cell or organism. All living processes are based on a complex series of chemical reactions. Metabolic processes fall into two types – those that build complex molecular structures from simpler molecules, called anabolism, and those that breaks down complex molecules into simpler molecules, called catabolism. Chemicals present in contaminated sites can be remediated through either, or both, of these processes.
Anabolism – Building Up
In anabolism, chemicals taken up by the microorganism are used to build various cell parts. Carbon and nitrogen are the basic chemicals in the proteins, sugars and nucleic acids that make up microbial cells. Microorganisms take up carbon and nitrogen from the soil, water, and air around them. In order to take up nutrients and make them into cell parts, a microorganism needs energy. This is where catabolism comes in.
Catabolism – Breaking Down
Catabolism allows microorganisms to gain energy from the chemicals available in the environment. Although most microorganisms are exposed to light and to chemical energy sources, most rely on chemicals for their energy. When chemicals break down, energy is released. Microorganisms use this energy to carry out cellular functions, such as those involved in anabolism.
Anabolism and Catabolism's Role in Bioremediation
Chemicals present at contaminated sites become part of the anabolism and catabolism process. For example, hydrocarbons (part of the carbon family) present at sites with petroleum products can be taken up by microorganisms and used as building blocks for cell components.
Other chemicals that are important to a microorganism include chemical compounds in the phosphorus, potassium, calcium and sodium group. Microorganisms also need trace elements of other chemicals, including chromium, cobalt, copper, and iron, all of which can be available in abundance at contaminated sites.
Nature has mechanisms for self-renewal. The role of biotechnology in bioremediation is to efficiently apply these existing mechanisms to clean up environmental contamination.
Various microorganisms are being studied to see if they can remediate various chemicals often present at contaminated industrial sites. Also, scientists are currently looking into genetically engineering certain microorganisms to increase their ability to metabolize specific chemicals, such as hydrocarbons, in contaminated sites.
Current Research Areas in Bioremediation
More research needs to be done in order to completely understand the complex microbial processes which make bioremediation possible, especially the bioremediation of metals. Also, researchers are trying to understand why some microorganisms are better at degrading one kind of chemical than another.
The development of better in situ bioremediation strategies are also being studied. In situ treatments would be ideal since they cost less and are less disturbing to the environment. Currently, in situ treatments are problematic because naturally existing external conditions are too difficult to control (dense soil, cold conditions, etc.). Methods for better delivery of nutrients or microorganisms in situ and ex situ are being developed.
Bioremediation is very frequently used in natural resource industries, like forestry, mining, and energy. Some examples are as follows:
Bioremediating Oil & Gas Industry Wastewater
The oil industry uses bacteria to clean up pollution created by spills and underground leaks, and to clean up waste products from oil production.
Wastewater containing dissolved hydrocarbons make up the largest volume of waste material generated by the oil and gas industry. Some parts of hydrocarbons are very toxic and do not break down naturally. This wastewater is sometimes treated in bioremediation lagoons – enclosed ponds containing oil-degrading bacteria – before it goes out into the environment. However, this process is very time-consuming.
To remediate wastewater faster and more efficiently, Saskatchewan researchers developed a reactor that uses oil-degrading bacteria. The reactor, which uses bacteria from the Pseudomonas family, consists of a tubular structure with a bacterial film through which the wastewater is filtered.
Bioremediating Contaminated Sediment
Organic waste from sewage, pulp and paper mills, and steel/petroleum industries have contaminated many of the world's harbours, lakes, rivers and canals. They affect water quality and aquatic life, sometimes combining with other naturally existing compounds in water to produce foul-smelling toxic gases.
The most common way to deal with sediment contamination is to scoop it up and move it away for long-term storage or treatment. However, these procedures are expensive. As well, excavation disrupts the natural habitat of the aquatic plants and animals, and is not viable as a long-term solution.
Sustainable Development and Bioremediation
Bioremediation uses the resources available in nature to clean up contamination. Using biological processes, as in the case of bioremediation, usually means lowered costs compared to chemical treatment processes for various contaminated sites. It is also less disturbing to the environment. However, because it is a natural process, it requires time.
Bacteria Biotech: Developing Environmental Alternatives in the Oil Industry (Part I). The AgBiotech Infosource, Issue 42, January 1999. 16 December 2001 www.agwest.sk.ca/infosource/inf_jan99.pdf
New Remediation Technique Tops the LIST. S&E Bulletin, Environment Canada. 6 January 2002 www.ec.gc.ca/science/sandeoct01/article2_e.html
A Citizen's Guide to bioremediation. The Citizen's Guide Series, United States Environmental Protection Agency. 16 December 2001 www.epa.gov/swertio1/download/citizens/bioremediation.pdf
What is Bioremediation? Natural and Accelerated Bioremediation Research (NABIR), Lawrence Berkeley National Laboratory. 1 May 2002 www.lbl.gov/nabir
Primer on Microbial Genomics, Fun Facts. Microbial Genomics Gateway. 4 January 2002 www.microbialgenome.org/primer/facts.html
Guide to Biotechnology: Environment. Biotechnology Industry Organization. 6 December 2001 www.bio.org/er/environment.asp
Biotechnology and the environment, Unit 16. European Initiative for Biotechnology Education.
Bioremediation Research Needs. United States Department of Energy, Office of Science. 2 January 2002 www.er.doe.gov/production/ober/nabir/needs.html
Biogeochemical Processes: The Foundation for In Situ Bioremediation. United States Department of Energy, Office of Science. 16 January 2002 www.er.doe.gov/production/ober/nabir/institu.html
Microbes: Building Blocks for Biotechnology. AgBiotech Infosource, Issue 37, June 1998. 1 May 2002 www.agwest.sk.ca/infosource/inf_jun98.pdf
Concepts and Technologies for Bioremediation in Confined Disposal Facilities. Dredging Operations and Environmental Research (DOER), US Army Corps of Engineers. 1 May 2002 www.wes.army.mil/el/dots/doer/pdf/doerc11.pdf