This is a general informative paper on the topic of bioremediation.
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The Earth’s biomass is said to be composed of sixty percent bacteria,# meaning that more than half of the total weight of living organisms on this planet is comprised of individual organisms that are so small that they cannot be seen by the naked eye without the use of a microscope. To put this into perspective, one bacterium weighs approximately 0.00000000001 grams. Approximately 1.2 million species of bacteria are known to exist, and it is estimated that more than five million are in existence.# What is even more impressive than their sheer numbers is their ability to adapt and roles in various biological functions and chemical processes. Bacteria are more than just “germs,” but rather they hold quite an important position in the ecology and health of this world. They are found in almost all types of environments on Earth, from deep-sea thermal vents to, deep inside solid rock, to the cooling jackets of nuclear reactors.# Humans have harnessed the abilities of these organisms for pest control, agricultural purposes, antibiotics, and more.
Microorganisms like bacteria are indubitably important in the functioning of the natural world. In fact, in the past century, researchers and scientists have realized that they might be the key to undoing some of humans’ errors pertaining to the environment. They have been harnessing the abilities of bacteria to treat environments contaminated with a variety of organic and inorganic compounds in a technology called bioremediation. A great multitude of bacteria of this world have boundless potential in cleaning pollutants in many different contaminated environments, and this technology should be supported and utilized whenever possible, as it is a safer alternative than other methods used for waste disposal and site cleanup.
Bioremediation in defined by experts in the field, Barry King, Gilbert Long, and John Sheldon, as a “treatability technology that uses biological activity to reduce the concentration or toxicity of a pollutant. It commonly uses processes by which microorganisms transform or degrade chemicals in the environment.”# Basically, this technology utilizes various microorganisms like bacteria to clean up toxins in the environment. Bacteria and other organisms like fungi or plants are capable of degrading a great number of organic pollutants and can be used strategically to decontaminate water systems, the soil, and so on.
The idea behind bioremediation is simple enough: the activities of living organisms are used to clean up contaminations in the environment. This, in fact, is a naturally occurring process, but bioremediation stimulates or speeds up the process. Microorganisms that already exist in nature degrade various types of waste, but they need nutrients, carbon, and energy to survive and multiply, just like all living creatures.# Where the environmental pollutants are harmful to human beings and other fellow eukaryotes great and small, these prokaryotes are capable of breaking down specified organic contaminants to obtain food and energy. Typically, the pollutants are degraded into less harmful or harmless substances such as salts, gases like carbon dioxide, and water.5 Microorganisms are either introduced to or cultured in the polluted site, and potential waste clean ups include petroleum, arsenic, chlorinated compounds,# lube oils, alcohols, fuels, some solvents, simple and moderately complex organics, nitrogen- and oxygen-substituted compounds,7 and potentially more. More research and experimentation could prove fruitful in determining the potential of bioremediation being used for a multitude of other pollutants.
There are three types of strategies used to implement microorganisms and bacteria in a bioremediation project: biostimulation, bioaugmentation, and intrinsic treatment.# Biostimulation becomes an available option when testing shows “the presence of a viable native population or community of specific contaminant-degrading microbes already in the site.”7 This is the least invasive process because indigenous microbes are merely encouraged to grow by means of the ascertaining the proper environment and resources that they optimally live at. The vast majority of bioremediation successes have implemented the stimulation of native microbes. However, when testing shows that the native populations of microorganisms will not likely improve the amount of contaminants at a site, species of microbes are purchased and artificially introduced into the soil and/or water. This process is called bioaugmentation.
The bioaugmentation method has not proven quite as effective as biostimulation because there is no single species that can overcome every pollutant. In other words, there is no one “hero species”7 that is a specific pollutant destructor. Indigenous species have an advantage over introduced organisms because they are already adapted to the environment and food. The new species typically become undetectable within a few days after being introduced. That being said, there have been some successful projects where sites have become quickly remediated through addition of purchased specific degrading microbial products. Certainly there is a lot of potential for advances in this field to make the availability of safe, adapted, or engineered organisms that have viability as well as capability to destroy specific pollutants in the field.#
Finally, intrinsic treatment might be used if biostimulation and bioaugmentation are too expensive, slow, or found not to be viable options. This method allows nature to handle the pollutant in due course. This is an approved remediation strategy that requires “regular monitoring for specific site contaminants, microbial health and numbers, and possibly other parameters as appropriate.”7 This method is often used when cleanup sites require expenditure of tax dollars or the government would rather not pay for it. Of course, if contaminants do not show a steady decline, other methods must be implemented.
Long before environmental processes were regulated, bioremediation was already working towards maintaining public health. In other words, bacteria and other microorganisms have long been at work processing human wastes. Since ancient times when the Romans and others built intricate networks of sewers as early as 600 B.C.,8 microorganisms did the work of biodegradation of organic waste in the collection vats and lagoons that were constructed to prevent system backup and overload. Though the Romans thought this to be some sort of “self-purification,” in reality microscopic organisms that were not yet known to exist at that time metabolized the waste. Modern sewage systems still utilize microbial degradation of wastes.
Various federal cleanup acts in the United States began as early as the late 1800s as hazardous materials in the environment became a growing concern. The first environmental legislation that passed was the Rivers and Harbors Act of 1899.7 The Insecticide Act of 1910, the Federal Insecticide, Fungicide, and Rodenticide Act of 1947, and the Solid Waste Disposal Act and Water Quality Act of 1965 were some early attempts to directly control pollution. With the passage of the federal National Environmental Policy Act of 1962, the Clean Water Act of 1972, the Safe Drinking Water Act of 1974, and the creation of the Environmental Protection Agency in 1970, there was finally a means of regulating environmental health. However, after decades of waste dumping, chemical spills, atmospheric pollutants, and various other forms of disregard for the natural world, damage had already been done and still to this day occurs, whether intentionally or not. Preventive and remedial acts were necessary in preserving the delicate landscape.
The 1970s and 1980s marked the beginning of the age of remediation as the environmental future became a fundamental topic. “The realization that terrestrial, atmospheric, and aquatic resources might, in fact, be finite led some early visionaries to encourage legislation that required cleanup of this ‘mess’ and prophylactic measures to further inhibit degeneration of our natural resources.”# People began to realize that if they wanted their children to have available not only the wonders of but also the resources that the environment offers, they would have to nurture the land back to health and prevent further degradation. The Resource Conservation and Recovery Act (RCRA) and the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) greatly influenced the regulation of pollution and provided some incentive to properly dispose of wastes. Waste became a liability, and many companies did not want to focus their efforts on their primary business and would rather let qualified consultants and contractors handle waste management, treatment, and disposal. However, the CERCLA requirements for predisposal treatment, there is a term called “Potentially Responsible Party”9 which means that in U.S. industry, “as long as the waste exists, liability persists.”9 This means that if any contaminants from a business cause problems down the road, that company is still held responsible. Because this shadow of continuing liability exists, bioremediation is becoming an attractive means for waste cleanup since contaminants are completely destroyed or detoxified.
Aside from the benefits that contaminants are destroyed or detoxified and liability is eliminated, there are other incentives to use bioremediation as a means of pollution cleanup. According to King, Long, and Sheldon, the other major benefits of this technology include attractive economics, as bioremediation is often more cost effective than traditional waste disposal methods and jobs are created in the process; undisturbed environments with some methods of application; and it is universal, meaning that is can often treat water, soil, sludges, and air.# Though bioremediation is not right for every pollutant situation, when it is a plausible form of decontamination, it does great things.
The people opposed to bioremediation projects are generally uneducated about all the facts, likening the process to something from a science fiction novel hearing and nothing of the many successful remediation projects. The fact that bacteria are applied to these sites alarms some people because they think bacteria are scary.10 Many people associate bacteria with disease and sickness, but the truth of the matter is that bacteria are everywhere, and though pathogenic species do exist, thousands of different kinds live among and inside humans symbiotically as well. To put it into perspective, “There are ten times more microbial cells on or in the human body than there are cells making up the body” (Black 404). This means that there are more foreign cells on our person than makes up our person! This reinforces the idea that bacteria are not the scary “germs” that some people associate them with. Certainly they can do great things, both to the detriment and to the benefit of the human population. Bioremediation is one way to harness this power in a positive light.
Others cannot agree with the process of introducing foreign organisms into places they were never meant to be. While it is true that humans have destroyed entire ecosystems by carelessly introducing species to a foreign environment—the zebra mussels in the Great Lakes, for example—the species of bacteria that are introduced in bioremediation projects are not quite so invasive, if non-indigenous species are even used at all. “After addition, these introduced microbes often rapidly decrease in number and can become undetectable within a few days.”# Introduced bacteria tend not to remain at the site once treatments are completely through. As a general rule of thumb, people should not mess with Mother Nature, but in bioremediation people are attempting to work with the Earth for mutual benefits. It really is nature’s way to a cleaner environment.
Finally, if the ethical aspect of bioremediation is not disputed, the economical benefits are. Some argue without basis that it is not cost effective or cost efficient. While it is true that bioremediation is not an overnight fix, it can potentially save a large percentage of the cost of some other treatment technology in the long run. There is always a risk in trying any procedure, but “the most that can be at stake if bioremediation proves ineffective is possibly two months of time and several thousand dollars in expense.”11 However, if it does prove successful for a particular site, it is drastically more economical than standard procedures, if money is what is important. At the very least, bioremediation should at least be considered if microbe-degradable contaminants are present.
One relatively recent bioremediation project from 1994 to 1995 involved the cleanup of approximately 6,000 cubic yards of soil contaminated with fuel oil, a liquid petroleum product.12 At a central California winery, a former underground storage tank held fuel oil that was used in the boiler operation at the winery. Over time, the fuel oil leaked through the wooden storage tank and accumulated in the surrounding soil. The site was a potential candidate for bacterial remediation, and so the soil was "excavated, removed, and spread out on an adjacent four-acre field."12 The case study does not specify why it had to have been transported. Twelve treatment cells were marked and constructed, presumably to test and compare different variables. After this, a series of soil sampling and chemical analysis determined the initial petroleum-hydrocarbon concentration, pH, and moisture content. Just as in science experiments, without this initial data collection, the success of the project could not be determined. After all the preliminary tests were finished, products consisting of vitamins, minerals, bioenhancement liquid nutrients, and other compounds were added to a 4,000 gallon water truck, along with "naturally occurring hydrocarbon digesting microorganisms.”# This mixture of supplements and organisms was then evenly applied to the treatment cells. This procedure was repeated three times over the summer season. Intermittent soil mixing and aeration occurred, along with additional water added to the twelve cells to maintain a reasonable moisture content. After these months of treatment, the soil was again sampled and analyzed, and the results are proof of the success of this particular bioremediation project. "After one month of treatment and prior to the second scheduled treatment.... the petroleum hydrocarbon concentration in the cells ranged from 940 to 2,600 mg/kg with an average of 1,820 mg/kg, or a 43% reduction."12 Only a month into the project and nearly half of the pollutants had already been degraded. After eleven months, chemical analysis indicated that the total petroleum hydrocarbon concentration was reduced from upwards to 4,550 parts per million to 125 parts per million. The target level for closure was 100 parts per million. Regulatory agencies granted closure to the site after further testing and results indicated that the concentrations no longer posed a threat to human health or the environment.#
In this case study, the soil was cleansed, but biological remediates have the potential to detoxify unwanted contaminants in the atmosphere, rivers, streams, and the ocean as well. Just recently in the spring and summer of 2010, bioremediates helped to clean up one of the largest accidental marine oil spills in the history of the petroleum industry.# They proved to be more effective than the chemical dispersants ejected into the oil and gas from BP’s Deepwater Horizon oil spill, and markedly less obtrusive. Because of microorganisms’ impressive abilities to digest that which humans cannot otherwise decompose, ecologists are examining the abilities of a number of prokaryotes to carry out bioremediation of various environments.# Scientists have already sequenced the genomes of at least seven different prokaryotic species, including one bacterium that is of particular interest; Shewanella oneidensis can metabolize more than ten elements in the presence and absence of oxygen. For example, it can convert soluble uranium, chromium, and nitrogen into insoluble forms that are less likely to leach into streams or groundwater. These are exciting studies and should be further endorsed. Bioremediation is not only a viable means to clean pollutants, but it also is the most harmonious way to involve ourselves in the purifying of our land.
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