Technical Abstract: Nitrification is a necessary and often limiting process in animal waste treatment for removal of nitrogen as N2 through biological nitrification/denitrification systems. We evaluated three technologies for enhancing nitrification of swine lagoon wastewater prior to denitrification: overland flow, trickling filter, and a bioreactor using nitrifying pellets. The overland flow system consisted of a 4- by 20-m plot with 2 percent slope receiving a total N loading rate of 64 to 99 kg N/ha/d. Total N removal efficiency ranged from 35 to 42 percent, and 7 percent of the total N application was recovered in the effluent as nitrate. The trickling filter consisted of a 1-cu.m tank filled with marl gravel media which supported a nitrifying biofilm. Lagoon wastewater was applied as a fine spray on the surface at hydraulic loading rates of 684 L/cu.m/ d and total N loading rates of 249 g/cu.m/ d. The media filter treatment transformed up to 57 percent of the inflow total N into nitrate when wastewater was supplemented with dolomitic lime. The nitrifying pellets technology used acclimated nitrifying cells immobilized in 3- to 5-mm polymer pellets. Swine wastewater was treated in an aerated fluidized reactor unit with a 15 percent (w/v) pellet concentration. Nitrification efficiencies of more than 90% were obtained in continuous flow treatment using total N loading rates of 438 g N/cu.m/ d and hydraulic residence time of 12 h. Two conclusions are suggested from this research: (1) that substantial nitrification of lagoon swine wastewater can be attained particularly using aerobic treatments with enriched nitrifying populations; and (2) that large mass removal of N from swine wastewater may be possible by sequencing nitrification and denitrification unit processes.