A CFD Model for Prediction of the Role of Biomass Growth and Decay on the Aerobic Biodegradation of BTEX Fate and Transport in an Unconfined Aquifer System

Abstract

This paper investigates the importance of considering biomass growth and decay for predicting a field scale microbial degradation of BTEX plume in an unconfined aquifer system in the Pump station area of Tehran oil refinery (TOR), Iran. A two-dimensional finite volume model has been presented to predict multi-species reactive transport incorporating physical, chemical and biological processes in the saturated zone of the aquifer. A multi-purpose commercial software called PHOENICS was modified to solve model equations. A complex Monod approach considering microbial growth and decay employed to describe the biodegradation of BTEX. The results of Monod approach was compared to those results obtained by three kinetics models including zero-order, first-order and Michaelis-Menten expressions that do not support biomass growth and decay. Monod approach predicted a further spreading of the plume. Other kinitics models underestimated the concentrations of BTEX plume, due to neglecting a high bacterial population and increased uptake rate. They are not appropriate to simulate tansport of biodegradable BTEX in the study aquifer. The model predictions agree well with the field measurements with an average error of 5%; describing that the Monod kinetics was well able to simulate the behaviour of the BTEX plume due to supporting bacterial population and considering oxygen as the electron acceptor.