Bioremediation Treatability Studies for Soils Containing Herbicides , Chemicals and Petroleum Products

Many organic chemicals have known human and environmental health hazards. At sites where chemicals have historically been stored, mixed and transferred, spills have often occurred. A primary route for human exposure to hazardous chemicals is by drinking groundwater which has been contaminated due to spills onto soil (Wilson et al., 1986) Due to the potential human health risks associated with exposure to hazardous chemicals, it is desirable to restore contaminated sites by the removal of pollutants. Conventional remediation methods often involve pump-and-treat schemes for contaminated water, and excavation and burial of contaminated soil in hazardous waste landfills. These methods increase the risk of exposure to pollutants for workers and local residents. Furthermore, these methods merely involve the transfer of pollutants from one environmental compartment to another, and are rather costly. Bioremediation is another method available for the restoration of contaminated sites. Advantages of bioremediation include competitive costs, pollutant destruction and minimal environmental disturbance. By biodegrading organic pollutants on site, exposure to pollutants is minimized and costs are reduced. One of the disadvantages of bioremediation is performance uncertainties in low permeability soils. Despite these potential reliability problems, bioremediation can potentially be an effective, low-cost and terminal solution for remediation of sites contaminated with organic pollutants. Many organic compounds, petroleum products in particular, are known to be biodegraded by indigenous microorganisms. The goal of bioremediation is to accelerate the biodegradation rates of naturally occurring microorganisms that utilize organic pollutants as a food source. An additional and important benefit of biodegradation as a remediation strategy is that pollutants are transformed into harmless products and not merely transferred to another environmental compartment (e.g. landfilling). Often the limiting factor controlling natural biodegradation processes are easily manipulated environmental parameters such as moisture, pH. oxygen availability and nutrient limitations (N, P). The manipulation of environmental conditions to accelerate naturally occurring biodegradation processes is bioremediation. Several carefully controlled successful field demonstrations of bioremediation have taken place in recent years.