This paper describes the extensive modeling carried out to determine the design expansion requirements for each unit process of the Littleton/Englewood wastewater treatment plant. The Mass Balance Model allows an accurate determination of the number and size of each unit process in the plant. Studies of alternative post-denitrification processes are presented, together with details of the final options selected for implementation at the plant. Various full-scale operating plants were visited which included MBBR, BAF and denitrification filter technologies for denitrification with methanol. The results of pilot plant trials using BAF technology at the Littleton/Englewood wastewater treatment plant are described. Implementation of an intra-plant denitrification recycle is described. The results of full-scale tests are presented. By incorporating the intra-plant recycle, redundant post-denitrification units are avoided. Other ancillary benefits include the attenuation of odors in preliminary and primary treatment processes.