Experimental investigation of microbial growth in subsurface environment

Abstract

An experimental investigation was conducted to quantify the permeability reduction caused by enhanced biological growth in a porous media. Studies were conducted using columns packed with sand of three different sizes (0.2, 0.3, and 0.4 mm). Phenol was used as a growth substrate. The study involved three distinct Phases with three different concentrations of phenol (15, 50 and 100gm/l). Variations in piezometric head, substrate concentration, and biomass measured as volatile solids, were monitored in space and time.

The reductions in permeability were found to be 78% for the coarse, 93% for medium size, and 93.7% for fine sand in Phase-I; Similarly in Phase-II, the reductions were 88.4% for coarse sand, and 94.6% for medium size sand. Finally, in Phase-III, the reductions were 95.5% for medium size, and 96.8% for fine sand. For aerobic sand media, volatile solids can be described as a function of influent substrate concentration respectively. The modified Kozeni-Carman equation was used to estimate the thickness of biological film, knowing the biofilm affected permeability. The estimated values of the film thickness varied from 0.06 mm to 0.09 mm. A good correlation was observed between porosity and biofilm thickness in low range values of thickness.