Production of nitrous oxide from anaerobic digester centrate and its use as a co-oxidant of biogas to enhance energy recovery.
Coupled Aerobic-anoxic Nitrous Decomposition Operation (CANDO) is a new process for wastewater treatment that removes nitrogen from wastewater and recovers energy from the nitrogen in three steps: (1) NH4(+) oxidation to NO2(-); (2) NO2(-) reduction to N2O gas; and (3) N2O conversion to N2 with energy production. In this work, we optimize Steps 1 and 2 for anaerobic digester centrate, and we evaluate Step 3 for a full-scale biogas-fed internal combustion engine. Using a continuous stirred reactor coupled to a bench-scale sequencing batch reactor, we observed sustained partial oxidation of NH4(+) to NO2(-) and sustained (3 months) partial reduction of NO2(-) to N2O (75-80% conversion, mass basis), with >95% nitrogen removal (Step 2). Alternating pulses of acetate and NO2(-) selected for Comamonas (38%), Ciceribacter (16%), and Clostridium (11%). Some species stored polyhydroxybutyrate (PHB) and coupled oxidation of PHB to reduction of NO2(-) to N2O. Some species also stored phosphorus as polyphosphate granules. Injections of N2O into a biogas-fed engine at flow rates simulating a full-scale system increased power output by 5.7-7.3%. The results underscore the need for more detailed assessment of bioreactor community ecology and justify pilot- and full-scale testing.
Stanford University , Stanford, California 94305-4020, United States.
Yaniv D
YD
Scherson
Sung-Geun
SG
Woo
Craig S
CS
Criddle
D064751:Ammonium Compounds / Q000378:metabolism; D000693:Anaerobiosis; D001419:Bacteria / Q000235:genetics; D061249:Batch Cell Culture Techniques; D056804:Biofuels / Q000032:analysis*; D019149:Bioreactors / Q000382:microbiology*; D003246:Conservation of Energy Resources; D009573:Nitrites / Q000378:metabolism; D009609:Nitrous Oxide / Q000378:metabolism*; D016877:Oxidants / Q000737:chemistry*; D010084:Oxidation-Reduction; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D062065:Wastewater / Q000382:microbiology; D018508:Water Purification
D064751:Ammonium Compounds; D056804:Biofuels; D009573:Nitrites; D009609:Nitrous Oxide; D016877:Oxidants; D012336:RNA, Ribosomal, 16S; D062065:Wastewater