A process based on partial nitrification and recirculation into the anaerobic digester was studied to remove nitrogen from digested manure and thus reduce enhanced gaseous ammonia emissions due to on-farm biogas production. An anaerobic reactor representing an anaerobic manure digester was fed with a nitrite solution and digested manure liquor. Nitrite was efficiently removed from the influent and ammonium formation was observed first. Ammonium was subsequently eliminated up to a maximum of 90% of the influent concentration, indicating anaerobic ammonium oxidation activity. This activity, however, decreased again and was lost at the end of the 4-month operation period. In a 1.5 L aerobic CSTR that was fed with digested manure liquor, ammonium was efficiently removed from the influent. Nitrite and nitrate formation was observed but mass balances indicated significant N-removal. Accumulation of suspended solids was observed at the end of the experiment suggesting presence of oxygen-free environments. In a second test in a 15 L CSTR where suspended solids sedimentation could be avoided, low N-removal rates were observed in the absence of biofilm carrier elements whereas high N-removal rates were achieved in their presence. A simple one-stage process based on immobilized biomass could therefore be installed downstream of agricultural anaerobic digesters in order to mitigate undesirable gaseous ammonia emissions.
Nitrogen removal from digested manure in a simple one-stage process
†Present address: EPFL ENAC INTER GR-GN, Station 18, 1015 Lausanne, Switzerland
J. D. Villegas, H. Fruteau de Laclos, J. Dovat, Y. Membrez, C. Holliger; Nitrogen removal from digested manure in a simple one-stage process. Water Sci Technol 1 May 2011; 63 (9): 1991–1996. doi: https://doi.org/10.2166/wst.2011.430
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