DETERMINATION OF SCALE-UP FACTORS FOR BIOVENTING IN THEVADOSE ZONE: THEORETICAL APPROACH - I

摘要

Spilled gasoline penetrates into the subsurface from a variety of sources, contaminatingboth the soil and groundwater. Bioventing is one of the technologies used to remediate the subsurface.However, geological, hydrological and climatological parameters affect the subsurface soil, creatingdifferent physico-biochemical environments from site to site, resulting in complicated degradationmechanisms. Consequently, it is difficult to extend laboratory-scale results to field-scale bioremediationdesign. For example, the biodegradation rate is typically controlled by scale-dependent phenomena suchas mass transfer mechanisms, presence of multiple phases and contaminants, competingmicroorganisms, spatial heterogeneities and toxicity. Understanding these mechanisms and phenomenaand simulating them in lab work will assist with the implementation of the laboratory results in the field. Toovercome these obstacles and reduce discrepancies that exist between the laboratory-scale and fieldscale,mesoscale and intermediate-scale reactors design has been undertaken. Variables that affect thebioventing performance the most in the field were integrated in the final design using Buckingham PiTheorem for structuring the physical relation between the variables and applied dimensional analysis formodeling. A dimensionless correlation was obtained in the form of dimensionless groups relating the firstorderrate degradation constant to a number of variables. These dimensionless numbers were adjusted toachieve two goals: obtaining an ideal soil reactor configuration and size; and obtaining the size of an idealextraction well. Optimum nutrients type, C:N ratios, soil moisture and method of addition and applicationas determined from the literature have been considered. The findings should improve the effectiveness oftransferring laboratory bioventing data to the field.