A model evaluating COD influence on a partial nitrification-Anammox biofilm process is integrated on the basis of heterotrophic growth as described in ASM3, combined with a previously published model for the CANON process. This integrated model can simulate the activities of heterotrophs and autotrophs involved in a biofilm, and interactions between COD oxidation, denitrification, nitrification and Anammox can be evaluated. Simulations indicate that COD in the influent has no important influence on the trends in the partial nitrification-Anammox biofilm process. Besides full COD removal, a total nitrogen removal efficiency of about 90% can be expected for stable biofilm systems. Furthermore, Anammox is a major contributor to the total nitrogen removal in stable biofilm systems and conventional denitrification only takes a share of <20% in the total nitrogen removal.