The dynamics of aerobic phenol biodegradation in lower greensand

Abstract

The dynamics of phenol degradation in sedimentary rocks was examined by percolating phenol solutions, with no added nutrients, through columns of disturbed Lower Greensand. Phenol degradation was achieved at concentrations up to 16.7 g dm−3. Inhibition was evident at higher concentrations. Sterilisation of Lower Greensand by moist heat or irradiation completely destroyed its ability to degrade phenol. Non‐growing bacterial cells attached to sand and clay particles were responsible for phenol degradation. Zero‐ and first‐order rate values for phenol degradation increased with increasing flowrate. First‐order kinetics operated with respect to substrate concentration. At flowrates of 1 cm3 h−1 (0.063 cm h−1) the reaction approached zero‐order at phenol concentration above 9.2 g dm−3 but at flowrates of 3 cm3 h−1 (0.19 cm h−1) increasing the phenol input concentration above 9.7 g dm−3 resulted in strong inhibition of activity. The results are explained in terms of phenol degradation being limited by the diffusion of phenol across a stagnant liquid film surrounding the microbes.