Partial nitritation of swine wastewater in view of its coupling with the anammox process

Partial nitritation (PN) of swine wastewater was investigated in a sequencing batch reactor (SBR) using a high-performance nitrifying sludge. Characteristics of the wastewater used were low content of biodegradable organic matter and a high alkalinity-to-ammonium ratio. The target oxidation of ammonium nitrogen (NH-N) to nitrite nitrogen (NO-N) was 57% (1.32 g NO-N g NH-N), which corresponds with the reaction ratio of the anaerobic ammonium oxidation (anammox). This target was successfully achieved at 32°C by controlling the inflow rate and the corresponding nitrogen loading rate (NLR). An average NLR of 1.47 g NH-N L d was applied to the partial nitritation sequencing batch reactor during a period of 70 d. The nitrite production rate obtained was 0.91 g NO-N L d. No nitrate was produced. The PN effluent contained 1.38 g NO-N g NH-N, which was within 5% of the target ratio. Under steady composition of the wastewater, the pH was shown to be a good indicator of the PN process performance. Furthermore, in a second sequencing batch reactor, the anaerobic ammonium oxidation process was effectively applied to the PN effluent, attaining a nitrogen conversion rate of 0.36 g N L d (14.3 mg N g volatile suspended solids h).