Partial nitritation (PN) of swine wastewater was investigated in a sequencing batch reactor (SBR) using a high performance nitrifying sludge (HPNS). Characteristics of the wastewater used were low content of biodegradable organic carbon and high alkalinity-to-ammonium ratio. Process temperature was 32°C. Target oxidation of ammonium nitrogen (NH4-N) to nitrite nitrogen (NO2-N) was 57% (1.32 g NO2-N g-1 NH4-N), which corresponds with the stoichiometry of the anammox reaction. This target was successfullly achieved just by controlling the inflow rate and corresponding N loading rate (NLR). An average NLR of 1.47 g NH4-N L-1 d- 1 was applied to the PN-SBR during a period of 70 days. The NO2-N production rate obtained was 0.91 g L- 1 d-1. No nitrate was produced. The PN effluent contained 1.38 g NO2-N g-1 NH4-N, which was within 5% of the target ratio. Under steady state conditions, the pH was shown as a good indicator of the PN process performance. Furthermore, in a second SBR the anammox process was effectively applied to the PN effluent attaining an N conversion rate of 0.36 g N L- 1 h-1 (14.3 mg N g-1 VSS h-1).