Modeling of remediation with ORC™:: Transverse dispersion

Oxygen release compound (ORC (TM)) is used to provide O-2 where costs or inconvenience of other sources make ORC a competitive source of O-2 for biodegradation. One application is the aerobic biodegradation of vinyl chloride and cis-1,2-DCE downgradient of anaerobic zones of natural attenuation or zero-valent metal permeable barriers. Small transverse dispersivities dictate that ORC wells be relatively closely spaced to avoid alternating strips of groundwater containing VOC or dissolved O-2 (D.O.) far downgradient from the wells (pin-striping). A model for ORC cleanups is described which includes transverse and longitudinal dispersion of both O-2 and contaminant. Biodegradation is handled by Monod kinetics. O-2 delivery capacity of a well is limited by Henry's Law and the hydrostatic head. Mineralization is assumed. Inclusion of transverse dispersion for both O-2 and contaminant results in less pin-striping than is modeled with O-2 dispersion alone. This permits somewhat wider spacing of the ORC wells. Dependence of results on model parameters is explored.