Modelling natural attenuation processes of phenol degradation in groundwater

Abstract

The ability to model subsurface natural attenuation (NA) processes at the field scale is desirable in order to facilitate understanding and management of contaminated sites. These field scale reactive transport models form numerically large systems, so it is important to use the simplest conceptual models for the reactive part. Currently, conceptual models of varying complexity are used. This work demonstrates that a full understanding of NA processes requires a very complex conceptual model. This is achieved by numerical modelling of a batch microcosm, in which phenol is degraded by a range of anaerobic processes typical of redox plumes. Microcosm carbon balance, redox balance, and temporal sequence of reactions were simulated. The conceptual model included aqueous and gaseous speciation, biomass growth using Monod kinetics, surface complexation, and precipitation. The redox reactions included fermentation to hydrogen and acetate intermediates, denitrification, manganese, iron and sulphate reduction, and methanogenesis. Field scale conceptual models which include transport processes as well are likely to be even more complex. The batch simulation offers the user a tool to assess that simplifications can be justified for the field scale conceptual model.