Experimental study of seepage flow properties with biofilm development in porous media with different filter morphologies

Abstract

Biofilm growth can impact seepage flow properties in the porous media, thereby affecting the performance of the infiltration systems. To better understand and characterize the biofilm distribution and its effect on seepage flow fields in the porous media with different morphologies, two-dimensional transparent flow cells were developed using X-ray images of zeolite, gravel, and ceramsite columns to study the effect of biofilm development and the pore structure on seepage flow properties. The results revealed that the filter morphology and biofilm growth significantly impacted the seepage flow field in porous media. With biofilm growth, a preferential flow pathway was more likely to be formed in angular filter cells (zeolite-shaped cells) than spherical filter cells (ceramsite-shaped cells). It was also found that microbial growth rate was closely related to seepage flowrate in 2D porous media cells. The biofilm grew faster in the areas with higher seepage flowrate. The biofilm accumulation did not seem to affect the location of the preferential seepage flow, probably due to the high permeability of the biofilm in the large pore throats. Although the water head loss of ceramsite-shaped cells was larger than that of two others due to its relatively smaller size of pore throat, the ceramsite-shaped cells presented small dead zone and short-circuiting, which means that ceramiste filter media had higher hydraulic efficiency.