Benzoate removal by aerobic bioslimes

Abstract

Studies of the aerobic biodegradation of sodium benzoate by bioslimes supported on an inclined plane are described. The objective was to simulate the trickling filtration process under carefully controlled laboratory conditions. The conventional method for correlating trickling-filter data is to plot the percentage (or fractional) removal of BOD vs some measure of the applied loading. When this procedure was applied to the data obtained in the study the significance of the resulting plots was obscure. This was despite a rigorous theoretical analysis that took into account the relevant mass-transport and biochemical-reaction processes. The true significance of the data was shown by replotting it in terms of the mean mass-flux of benzoate into the slime layer. The procedure revealed the variations in slime utilization (due to variations in loading) amongst the different runs. The commonly-accepted basis of the design equations found in the literature for trickling filters is a correlation of substrate removal data in terms of fraction of substrate removed. This study shows that the conventional procedure is a basically unsatisfactory appproach. Instead plots of mean mass-flux vs some measure of the applied loading (such as mass per unit time, or inlet concentration) are recommended. The intrinsic kinetics for the benzoate-removal process within the bioslime layer was zero order and the value of the zero order rate constant was estimated to be about 1 × 10 −7 g cm −3 s −1 (at temperatures in the range 17.5–23.5°C).