Engineering concepts for in situ bioremediation

Abstract

Most organic materials that contaminate soil and the subsurface environment are readily degraded by natural biological processes. Thus, bioremediation can be thought of as a highly successful purification process. However, some organic molecules are naturally refractory to biodegradation, the proper microbial population is not present, or environmental conditions are not suitable to biodegradation so that the compounds become recalcitrant to biodegradation and persist in the environment for years. Where natural processes are slow, the best strategy may still be to wait for the natural degradation to occur because of the current high costs and lack of reliability of engineered solutions. In other cases, the natural recalcitrance may be changed by introduction of degrading populations of microorganisms or by changing the environmental conditions by introduction of chemicals or through mixing and dilution. The potential success of engineering procedures to enhance degradation rates also depends to a large degree upon the complexity of the hydrogeology at a given site. With complex hydrogeology, most remediation approaches are rendered difficult if not impossible. This must be recognized by regulatory authorities and the public. In such cases alternative strategies to site remediation itself should be sought. More attention to such alternatives is needed in order to reduce unproductive expenditure of scarce resources.