ARS | Publication request: Partial nitritation of swine wastewater in view of its coupling with the anammox process

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 3, 2012
Publication Date: May 15, 2012
Citation: Magri, A., Vanotti, M.B., Szogi, A.A., Cantrell, K.B. 2012. Partial nitritation of swine wastewater in view of its coupling with the anammox process. Journal of Environmental Quality. 41(6):1989-2000.

Interpretive Summary: Appropriate land application of manure nitrogen (N) at agronomic rates must be assured in order to preserve environmental quality of agricultural ecosystems, atmosphere, and water resources. When land is limiting due to concentrated livestock operations, the combined bioprocess of nitrification-denitrification has been used for the removal of nitrogen from wastewater through the conversion of ammonia into dinitrogen gas (N2). In this research we evaluated a more economical biological nitrogen removal process based on partial nitrification-anammox (anaerobic ammonia oxidation). This approach requires about half the aeration required by nitrification-denitrification, which significantly lower operational costs of treatment. Novel strains or mixtures of microorganisms discovered by USDA-ARS were used in the research: A high performance nitrifying sludge mix (HPNS), and a novel anammox isolate Brocadia caroliniensis. Using sequential bench reactors at bench scale, the research optimized the partial nitrification step and provide a balanced intermediate effluent for anammox. This was done by varying loading rates, aeration rates, and elements in the wastewater chemistry using swine wastewater containing > 1000 ppm ammonia nitrogen. A balanced intermediate effluent was successfully produced. Further, the intermediate effluent was effectively tested with anammox in a second reactor. The results obtained provided key information on the production of partially nitrified effluent suitable for the anammox process. This information is needed for scaling-up the process to develop more economical biological N removal system for livestock producers.

Technical Abstract: 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 matter and high alkalinity-to-ammonium ratio. Target oxidation of ammonium nitrogen (NH4-N) to nitrite nitrogen (NO2-N) was 57% (1.32 g NO2-N/ g NH4-N), which corresponds with the stoichiometry of the anaerobic ammonium oxidation (anammox) reaction. This target was successfully achieved at 32ºC just by controlling the inflow rate and corresponding nitrogen loading rate (NLR). On this regard, an average NLR of 1.47 g NH4-N/L/d was applied to the PN-SBR during a period of 70 days. The NO2-N production rate obtained was 0.91 g L/d. No nitrate was produced. The PN effluent contained 1.38 g NO2-N/g NH4-N, which was within 5% of the target ratio. Under steady composition of the wastewater, 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 a nitrogen conversion rate of 0.36 g N/L/h (14.3 mg N/g VSS/ h).