MODELING OF THE GROWTH OF A METHANOTROPHIC BIOFILM

A model describing the growth of a methanotrophic biofilm is presented . This model involves simultaneous growth of methanotrophs, heterotrop hs and nitrifiers. Heterotrophic biomass grows on soluble polymers whi ch arise from the hydrolysis of dead biomass entrapped in the biofilm. Nitrifiers develop because of the presence of ammonia in the mineral medium. A comparison of this model with experimental data showed that the biofilm growth, methane removal, oxygen consumption, product forma tion and biofilm detachment could be fitted well. Parameter estimation yielded a maximum growth rate for methanotrophs, mu m, of 1.17 +/- 0. 2 d(-1), at 20 degrees C, a decay rate, b(m), of 0.34 +/- 0.06 d(-1), a half-saturation constant, K-S(CH4), Of 0.08 +/-: 0.05 mg CH4/l, and a yield coefficient, Y-CH4, of 0.21 +/- 0.03 g x COD/g CH4 GOD. In add ition, a sensitivity analysis has been performed for this model. It in dicated that the most influential factors were those related to the bi ofilm (i.e. density; solid volume fraction; thickness). This suggests that in order to improve the model, further research is needed in the field of biofilm structure and composition. (C) 1997 IAWQ. Published b y Elsevier Science Ltd.