Two-dimensional flow-through experiments: versatile test systems for a combined investigation of transport and reactive processes in porous media

In the present study we report on the results of laboratory experiments aimed at investigating transport and diffusion/dispersion limited reactions in saturated porous media. In similar 2-D bench-scale set-ups we studied different processes, including transport of conservative tracers, fast abiotic mixing-controlled acid/base reactions, and contaminant biodegradation, including aerobic degradation and oxidation of petroleum hydrocarbons (i.e. toluene and ethylbenzene) coupled to nitrate reduction. The experiments were carried out in both homogeneous and heterogeneous porous media under steady-state and transient (i.e. oscillating) flow fields. The scale of the experimental set-up allowed high-resolution monitoring by combining a number of physico-chemical and microbiological methods. The laboratory experiments were always accompanied by numerical flow and transport simulations. We compared the modelling results with the observed data and we used different measures, including a newly defined flux-related dilution index, to quantify the mixing and the reaction extent under various experimental conditions.