Alternative novel biological nitrogen removal technologies may provide advantages over the conventional nitrification-denitrification nitrogen removal. One such advantage is the lower operating costs that these alternatives offer. As such, better understanding of these alternatives may prove to be beneficial. One of the alternatives involves the use of the novel anammox bacteria. To provide more information about anammox coupled processes, mathematical prediction was undertaken. Mathematical models of the nitritation: anammox-coupled biofilm in a co-diffusion (Rotating Biological Contactor or RBC) and counter-diffusion (Hollow Fiber Membrane Bioreactor or HFMBR) configurations were developed and implemented using AQUASIM to predict the effects of different start-up conditions and operational conditions, respectively. One of the modeling results had shown that oxygen concentration affects total nitrogen removal for the different reactor configurations. The modeling results provided information relevant for further study and investigation.