The principle objective of this research that was supported by the American Water Works Association Research Foundation was to evaluate the impact of recycling waste streams produced by the water treatment process back to the head of the plant. Recycle streams that were analyzed included spent filter backwash water (with and without solids removal), sludge thickener supernatant, lagoon overflow, belt press filtrate, and sand drying bed filtrate. The research also evaluated the effects of storing sludge in sedimentation basins. The main contaminants that are discussed in this paper are: giardia and Cryptosporidium cysts; TTHM and TTHM precursors; assimilable organic carbon (AOC); and manganese. Field-scale evaluations were conducted at eight water plants, with the full-scale data supplemented by laboratory study. Key findings, grouped by contaminant, are discussed in this paper.