A mathematical model and the simulation of subsoil decontamination by bioventing will be presented. The bases for the model construction are the following: (1) the pollutant is considered as immobile and confined in the unsaturated zone; (2) only oxygen is injected in the subsoil by wells;(3) the bacteria acting the pollutant removal are immobile and their growth depends on oxygen and pollutant concentration.

Here some issues are studied, related to the numerical solution of Richards' equation in a one dimensional spatial domain by a technique based on the Transversal Method of Lines (TMoL). The core idea of TMoL approach is to semi-discretize the time derivative of Richards' equation: afterward a system of second order differential equations in the space variable is derived as an initial value problem.The computational framework of this method requires both Dirichlet and Neumann boundary conditions at the top of the column. The practical motivation for choosing such a condition is argued. We will show that, with the choice of the aforementioned initial conditions, our TMoL approach brings to solutions comparable with the ones obtained by the classical Methods of Lines (hereafter referred to as MoL) with corresponding standard boundary conditions: in particular, an appropriate norm is introduced for effectively comparing numerical tests obtained by MoL and TMoL approach and a sensitivity analysis between the two methods is performed by means of a mass balance point of view. A further algorithm is introduced for deducing in a self-sustaining way the gradient boundary condition on top in the TMoL context.

Bioventing is a technology used to abate the presence of pollutants in thesubsoil.Microorganisms biodegrade the pollutant but the biochemical reactionrequires oxygen and so an airow is induced in the subsoil by means ofinjection and/or extraction wells.Costs, final result and decontamination time are reliant on contaminanttype, soil permeability and several other factors, but oxygen subsoil concentrationplays a very important role. For this reason a rational choice of welllocation and ow rate is required.The mathematical definition of the optimal design problem will be setupstarting from a simplified mathematical model describing the bioventingsystem.A formal definition of decontaminated subsoil will be given and the set ofsystem control variables will be identified. Several optimimization strategiessuch as cost minimization, removal rate maximization and time optimizationwill be mathematically described.

Bioventing is a subsoil bio-remediation technique which improves the activity of bacteria to transform contaminants into less hazardous compounds by inflating air through wells. The mathematical model describes the bacteria population dynamics and the dynamics of a multiphase, multicomponent fluid in porous media and in this paper a simple version of it will be described. A critical point of the design problem is to choose well positions and air flow rates to optimise the biodegradation process. The numerical simulation and some initial optimisation design results for the simple model proposed will be reported. The decontamination time required for different flow rates and for different well spatial configurations will be compared.

Bioventing is a clean-up technology essentially used to remove hydrocarboon from polluted subsoil by the action of microorganism. The model is based on the theory of fluid flows in porous media and on the mathematical description of population dynamics. The numerical results of a simplified model will be described.

A mathematical model describing the bioventing technique for the decontamination of pol-luted subsoil will be presented. Bioventing is a biological technique: bacteria remove thecontaminant transforming it and oxygen is consumed in the reaction. The numerical modelis based on the fluid flow theory in porous media and bacteria population dynamics andit describes: pollutant degradation, oxygen and bacteria concentration. The mathematicalmodel will be numerically solved and the results of some experiments will be presented.

Bioventing is a technology used to remove some kinds of pollutants from the subsoil and it is based on the capability of somebacteria species to biodegrade contaminants. The biochemical reaction requires, among other things, oxygen and, therefore,oxygen is inflated into the subsoil by wells. The mathematical model describes the movement of the different fluids whichare present in the subsoil - air, water, pollutants, oxygen and so on - and the bacteria population dynamics. The presence ofsource reactive terms in the continuity equations allows the contaminant biodegradation to be described.The design of a subsoil decontamination intervention concerns bioavailability problems and, in particular, the oxygenconcentration. Therefore, in order to enhance the biodegradation phenomenon, the optimization of the subsoil oxygen velocityfield in the polluted area is required, by an appropriate choice of the well positions and of the well air inflating rates. Inmathematical terms, the goal is to obtain the decontamination of the subsoil with an optimal value of an objective function byacting on some control variables which, in this case, are the well positions and the inflating rates. In this paper several kind ofobjective function are proposed.