MASS-TRANSFER MECHANISM IN BIOFILMS UNDER OSCILLATORY FLOW CONDITIONS

The objective of this research is to investigate mass transfer mechani sm in biofilms under oscillatory flow conditions, which provides valua ble information for the understanding of self-purification by biofilms under oscillatory flow conditions like in coastal areas. A mathematic al model was developed to describe substrate profiles in biofilms unde r oscillatory flow conditions, which suggested that substrate uptake r ate by biofilms is proportional to the square root of the Reynolds num ber. A laboratory-scale channel with a wave generator was prepared, in which plastic plates were used as substratum for biofilms. Glucose wa s used as a substrate. Velocity and turbulence profiles near the biofi lm were measured by a laser Doppler velocimeter. The cycle of the wave generator was changed and its short-term effect on the substrate upta ke rate by the biofilm was measured. The substrate uptake rate decreas ed with the decrease of the Reynolds number of the wave motion accordi ng to a power law with a coefficient of 0.6; which suggests that subst rate transport in biofilms under oscillatory flow conditions is carrie d out by turbulent diffusion caused by oscillatory flow motions over b iofilms. (C) 1997 IAWQ. Published by Elsevier Science Ltd.