Growth kinetics of Pseudomonas fluorescens in sand beds during biodegradation of phenol

The growth kinetics of a bacterium of the strain Pseudomonas fluorescens, which is indigenous in soil, has been investigated in batch cultures and sand packs during biodegradation of phenol. Batch experiments were conducted at 25 °C with four different initial concentrations of phenol for the estimation of the kinetic parameters. Phenol was found to inhibit microbial growth and so Andrews's model was used to describe the growth rate. Growth kinetics in sand packs was studied in a series of eight virtually identical columns, which were operated simultaneously under the same conditions and in a continuous flow mode, with phenol as the sole carbon source. The idea of eight columns allowed monitoring of biomass growth as a function of time. Every 1 or 2 weeks, one column was drawn out of the system and was “sacrificed” to measure the developed biomass in the porous medium. The results indicated that growth of P. fluorescens in sand packs during biodegradation of phenol was an intensely dynamic phenomenon. Detachment of clusters of bacteria from the sand grains was found to be one of the main processes taking place in such a system, caused by a combination of low nutrient supply, oxygen availability and flow velocity.