Sensitivity Study on the Classical Biofilm Model Using a Simplified Solution Method

The classical biofilm model depicts correlation between the substrate concentration in influent and effluent as well as at liquid--biofilm interface, substrate flux, biomass density, specific surface area, hydraulic retention time, solid retention time, etc. This correlation is represented by a set of algebraic equations, which are implicit in nature. Solution of this biofilm model appeared to be complicated, tedious, time-consuming, and also approximate. The extent of influence of each process variable on the performance of a biofilm system is an important issue for optimization purpose. In view of that, a simplistic solution of the classical biofilm model has been proposed which enables one to estimate the model output quickly and also accurately under any given set of input variables. Thus, the crucial process variables like input substrate concentration (S₀), biomass density (X_f), hydraulic retention time (Ə) and specific surface area (a) are varied suitably within their feasible ranges in the present study. Finally, all the relevant outputs like substrate concentration in effluent and at liquid--biofilm interface (S_e and S_s), substrate flux (J) and effective as well as steady-state biofilm thickness (L_e and L_f) were plotted against the respective input variables to investigate their sensitivity.