Monod expressions are typically preferred over zero-and first-order decay expressions in contaminant transport and biotransformation modelling. The use of a single-value decay rate in first-order models, although not accurate, is an easy practice to predict biodegraded contaminant mass. On the other hand, Monod expressions, although accurately representing subsurface complex conditions, do not reveal the biodegraded mass without dense numerical modelling. Additionally, the wide range of values of Monod parameters makes any case study unique. Such uniqueness restricts the usefulness of natural attenuation studies and limits the utility of their outcomes to a limited number of similar cases. A need, therefore, appears for the development of simplified dimensionless parameters that could ease the description and evaluation of natural attenuation case studies; and it therefore accelerates research development in this field. Several dimensionless parameters are developed to evaluate the effect of electron acceptor inhibition on microorganisms when added to enhance contaminant biodegradation.