Recycle streams are the liquid streams which result from almost all solids processing within a wastewater treatment plant, including separation, thickening, treatment, dewatering, and disposal. In most cases, these streams are returned to the plant for treatment, and impose a substantial load in terms of five-day biochemical oxygen demand (BOD5), suspended solids, nitrogen, phosphorus, and hydraulics. This additional load will affect the operation of the treatment plant and could degrade effluent quality. In order to control recycle streams, and minimize their effect on the plant, the source of each stream must be identified, their effect on the overall operation of the plant must be evaluated, and a plan for control developed. This paper discusses these unit processes which produce the most severe recycle streams. Case studies are presented which demonstrate the impact of recycle streams on plant operation, and the strategies employed to mitigate those impacts.