The remediation of a site contaminated with one or more hazardous chemicals normally involves removing, destroying, or stabilizing in place the chemicals of concern. Chemical destruction or stabilization generally involve chemical or biological reactions that require the bringing together of the contaminant with one or more chemical or biological ingredients necessary for the reaction to proceed. For example, the aerobic biological destruction of the gasoline derived contaminant benzene in groundwater would require that oxygen be present or introduced in some manner and mixed with the benzene so that naturally occurring microorganisms residing within the aquifer could bring about benzene oxidation to carbon dioxide and water. Nutrients for growth of the microorganisms, such as nitrogen and phosphorus, may also need to be added to sustain the reaction. Additionally in some cases, acidic or basic chemicals such as hydrochloric acid or sodium bicarbonate may need to be mixed in with the water to achieve a pH condition that is satisfactory for biological growth. In some cases, such as in the anaerobic biological destruction of vinyl chloride, special strains of microorganisms may also need to be added as they may not be present naturally in the aquifer. In all such cases, the important processes of mass transfer and mixing are involved. Because of the complexity of aquifer systems, such mass transfer and mixing often becomes one of the most difficult and expensive aspects of site remediation. Thus, it behooves the designer or operator of a remediation system to be well versed in the fundamentals and applications of mass transfer and mixing processes as they apply to aquifer systems. The purpose of this volume is to aid in that understanding.
KeywordsBiomass Phosphorus Dioxide Benzene Microbial Degradation
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