What is Bioremediation?
Bioremediation is the controlled use of biologically active systems to bring about desired chemical and /or physical changes in a confined and regulated environment. These desired changes include:
The process is biological, nature’s method of dealing with wastes which can be eliminated from the environment through natural decomposition. It is Nature’s “Technology of Choice”. Bioremediation through bio-enhancement accelerates the process, and in most cases, is clearly superior and less costly than conventional methods.
How Does It Work?
Bioremediation consists of using techniques for enhancing naturally occurring microorganisms that can biologically transform and/or eliminate the pollutants, and bringing these microorganisms into intimate contact with the pollutants. Microorganisms such as bacteria and fungi have been shown to be effective and important in bioremediation processes. Most research has to date centered on the use of bacteria, but fungi can play an important role in bioremediation processes, especially with halogenated compounds. In almost all cases, the bioremediation process relies on diverse populations of microorganism species, rather than on one or a few species.
Bioremediation vs. Conventional Methods
Normal practice prior to the availability of efficient bioremediation processes has been to excavate contaminated soils or sludges and haul them away to some landfill or incinerator facility. Landfills are becoming more restrictive and incineration costs are high and expected to increase. To the cost of landfilling and expenses that must be added for excavation, loading, transportation and replacement with clean fill. Moving contaminants also involves risks.
Bioremediation – accelerating the natural on-site biological cleanup processes offers a safer and less expensive alternative in most cases.
The Bioremediation Process
Bioremediation is achieved through bio-enhancement, the addition of large numbers of selected naturally occurring microorganisms. With bio-enhancement, a sufficient amount of selected microorganisms are applied to the soil to give an initial population of approximately one million per gram of soil. Studies have shown that this concentration insures that an efficient population of organisms will increase up to one thousand fold as they digest the contaminates. Bio-enhancement greatly increases the rate of degradation compared with the natural process because of the low numbers of naturally occurring microorganisms present in the soil.
Generally a contaminant must move through the waste/soil matrix and pass through a microorganism’s cell membrane in order for the microorganism to transform the contaminant, although, in some cases, contaminants can be transformed by extracellular enzymes without entering into the microorganism. Several physical and chemical parameters must be controlled in order to obtain optimum biological activity and maximum degradation of contaminants. These parameters include soil, oxygen and nutrient concentrations, as well as temperature and moisture conditions.
Any on-site bioremediation process utilizing microorganisms requires an in-depth knowledge of site conditions in order to be effective. Projects should begin by analyzing soil samples from a given site to determine both indigenous microorganism populations and contaminant constituents. This information is required to determine biodegradability and the proper types of microorganisms, nutrients and conditions needed. Mixtures of site specific microorganisms are then prepared and quantities grown for inclusion in the site treatment. At the same time, site conditions are prepared for eventual application. Once field applications begin, process development is monitored through regular on-site tests. This measures remediation progress and indicates if any adjustments are needed. When testing shows that the required level of cleanup has been achieved, a final test audit is performed.
Areas of Application
Bioremediation has been successfully used in a variety of applications to date. The methods of application vary depending on specific site conditions.