Bioremediation technologies utilize naturally occurring microorganisms, such as bacteria, fungi, and yeast, to degrade hazardous substances into non-toxic or less toxic substances. There are several advantages of using bioremediation processes compared with other remediation technologies: (1) biologically-based remediation detoxifies hazardous substances instead of merely transferring contaminants from one environmental medium to another; (2) bioremediation is generally less disruptive to the environment than excavation-based processes; and (3) the cost of treating a hazardous waste site using bioremediation technologies can be considerably lower than that for conventional treatment methods.
The bioremediation technology most suitable for a specific site is determined by several factors, such as site conditions, indigenous microorganism population, and the type, quantity, and toxicity of contaminant chemicals present. Some treatment technologies involve the addition of nutrients to stimulate or accelerate the activity of indigenous microbes. Optimizing environmental conditions enhance the growth of microorganisms and increase microbial population resulting in improved degradation of hazardous substances. However, if the biological activity needed to degrade a particular contaminant is not present at the site, suitable microbes from other locations, called exogenous microorganisms, can be introduced and nurtured. Other technologies being demonstrated are phytoremediation, or the use of plants to clean up contaminated soils and ground water, and fungal remediation, which employs white-rot fungus to degrade contaminants.
Bioremediation applications are categorized as either in situ orex situ . In situ applications treat contaminated soil or water in the location in which they are found. Ex situ bioremediation requires excavation or pumping of contaminated soil or groundwater, respectively, before treatment is initiated. In situ techniques are generally less expensive, generate less dust and debris, and release less contaminants than ex situ techniques because no excavation processes are required. On the other hand, ex situ techniques are generally easier to control, faster, and able to treat a wider range of contaminants and soil types than in situ techniques.
The lack of understanding of processes and control currently limit the use of bioremediation. There is a need for greater understanding of suitable engineering techniques to broaden the applicability of the technology. Additionally, reliable cost data is needed to command full acceptance and widespread use by technical and regulatory entities.