Biodegradation of Sulphide in Biogas by Biofilm on Salak Fruit Seeds: Accuracy of Quasi-steady-state Approximation

Abstract

This study tried to explore the quantitative description of removal of hydroden sulphide (H2S) by bio-filtration. H2S is degraded by bacteria immobilized on the packing materials of Salak fruit seeds inside a column. Two kinetics models are proposed. In both models, the biofilm formed on the packing material is assumed to be thin, so intra-film gradient of H2S concentration can be neglected. In model 1, material balances of H2S in the bio-film as well as in the flowing gas are set-up. The growth of the bio-film is modelled by Monod’s equation. A set of three simultaneous partial differential equations are obtained. Model 2 is set-up using the same concepts as in model1, but the gas phase is assumed to be quasi-steady-state. This assumption reduces the partial differential equation in model 1 to be an ordinary differential equation which is easier to be solved. The comparisons of the results of model 1 and model 2 can be applied to justify the applications of quasi-steady-state approximation. It turned out that the differences of calculated H2S concentration results are approximately small, around 6 ppm. Hence, it can be concluded that quasi-steady-state approximation in the gas phase is suggested to be applied.