Nitrogen removal as nitrous oxide for energy recovery: Increased process stability and high nitrous yields at short hydraulic residence times

WATER RESEARCH

卷:173

Article

Wang, Zhiyue^1,2  Woo, Sung-Geun^1,2  Yao, Yinuo^1,2  Cheng, Hai-Hsuan³  Wu, Yi-Ju³  Criddle, Craig S.^1,2 

[1] Stanford Univ, Dept Civil & Environm Engn, Stanford, CA 94305 USA

[2] Natl Sci Fdn, Engn Res Ctr Re Inventing Nat Urban Water Infrast, Stanford, CA USA

[3] Natl Cheng Kung Univ, Dept Environm Engn, Tainan, Taiwan

关键词: Anaerobic digester centrate;    Denitritation;    Nitrous oxide;    Polyhydroxyalkanoate;    Short-cut nitrogen removal;    Wastewater;   

DOI  :  10.1016/j.watres.2020.115575

来源: Elsevier

【 摘 要 】

The Coupled Aerobic-anoxic Nitrous Decomposition Operation (CANDO) is a two-stage process for nitrogen removal and resource recovery: in the first, ammonia is oxidized to nitrite in an aerobic bioreactor; in the second, oxidation of polyhydroxyalkanoate (PHA) drives reduction of nitrite to nitrous oxide (N2O) which is stripped for use as a biogas oxidant. Because ammonia oxidation is well-studied, tests of CANDO to date have focused on N2O production in anaerobic/anoxic sequencing batch reactors. In these reactors, nitrogen is provided as nitrite; PHA is produced from acetate or other dissolved COD, and PHA oxidation is coupled to N2O production from nitrite. In a pilot-scale study, N2O recovery was affected by COD/N ratio, total cycle time, and relative time periods for PHA synthesis and N2O production. In follow-up bench-scale studies, different reactor cycle times were used to investigate these operational parameters. Increasing COD/N ratio improved nitrite removal and increased biosolids concentration. Shortening the anaerobic phase prevented fermentation of PHA and improved its utilization. Efficient PHA synthesis and utilization in the anaerobic phase correlated with high N2O production in the anoxic phase. Shortening the anoxic phase prevented reduction of N2O to N-2. By shortening both phases, total cycle time was reduced from 24 to 12 h. This optimized operation enabled increased biomass concentrations, increased N2O yields (from 71 to 87%), increased N loading rates (from 0.1 to 0.25 kg N/m(3)-d), and shorter hydraulic residence times (from 10 to 2 days). Long-term changes in operational performance for the different bioreactor systems tested were generally similar despite significant differences in microbial community structure. Long-term operation at short anaerobic phases selected for a glycogen-accumulating community dominated by a Defluviicoccus-related strain. (c) 2020 Elsevier Ltd. All rights reserved.

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