BACKGROUND: Considering biological nitrogen removal, the partial nitritation connected with the anaerobic ammonium oxidation (anammox) process is a promising alternative for nitrogen elimination at high loading rates. The objective of the present study was to evaluate the establishment and operation of a partial nitritation process in an airlift reactor with simultaneous removal of total organic carbon and suspended solids using swine wastewater. RESULTS: The partial nitritation reactor was inoculated with a nitrifying sludge at 2.1 gTSS L-1 and fed with an UASB reactor effluent. High organic carbon loading rates, above 2 kgTOC m(-3) d(-1) have been shown to be potential inhibitors of the partial nitritation process due to competition between autotrophic and heterotrophic bacteria. In this study, the partial nitritation process was established using undiluted swine wastewater, with HRT of 24 h, 1.84 mgO(2) L-1 (SD = 0.41) DO, loading rate of 1.14 gTOC L-1 d(-1) and 0.91 gN-NH3 L-1 d(-1) for more than 100 consecutive days. At the same time, the system proved to be an effective tool in TOC and TSS removal, reaching 84.9% (SD = 9.3) and 83.1% (SD = 0.1), respectively. CONCLUSION: This result enhances partial nitritation application as a technology for high load nitrogen converting, and allows the possibility of connection with anammox reactors. Copyright (c) 2012 Society of Chemical Industry