A study of distribution of biofilm in porous media and its effect on permeability
孔隙介质中生物膜空间分布及其对渗透性影响研究

Microorganisms built up on the grains of porous media under condition of ground water bioremediation, which resulted in bioclogging and impacted on the efficiency of bioremediation. The distribution of biofilm thickness on individual sand grains in a two-dimensional sand-filled cell was investigated. It followed a normal distribution. The existing quantitative models, which described the relationship between biofilm thickness and permeability, generally assumed that the particles were uniformly coated by biofilm with constant thickness. However, the assumption was not consistent with the experiments' results. To investigate the effect of the variability of biofilm thickness on permeability, six different Taylor's models were used to calculate reductions in porous media permeability as a function of biofilm thickness. The results indicated that the biofilm thickness had a significant impact on outcomes of the models. Reductions of permeability with the minimum biofilm thickness were 1~4 orders of magnitude greater than the relative permeability with maximum biofilm thickness by the Mualem model. Different models had different sensitivities to biofilm thickness. The Mualem model had the highest sensitivity among the six models. Permeability reductions predicted by the Mualem model with mean biofilm thickness were consistent with experimental measurements of reductions in permeabilities. Therefore, mean biofilm thickness might be a good representative for permeability reduction prediction. Mualem model was more suitable for calculating the change of permeability in porous media under condition of bioclogging.