Pilot-scale study of step-feed anaerobic coupled four-stage micro-oxygen gradient aeration process for treating digested swine wastewater with low carbon/nitrogen ratios

• Published in: Bioresource technology Vol. 380; p. 129087
• Main Authors: Tang, Hang, Ma, Zhuang, Qin, Yong, Wu, Hanghang, Xu, Xingkun, Xin, Liqing, Wu, Weixiang
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.07.2023
• Subjects: Anaerobiosis; Animals; Bioreactors; Carbon; Denitrification; Low dissolved oxygen; Mass balance; Nitrification; Nitrite accumulation; Nitrogen; Nitrogen removal; Oxygen; Sewage; Simultaneous partial nitrification and denitrification; Swine; Wastewater; Mass balance; Nitrogen removal; Low dissolved oxygen; Nitrite accumulation; Simultaneous partial nitrification and denitrification
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2023.129087

[Display omitted] •A low oxygen energy consumption method proposed to treat DSW with low COD/TN ratio.•Low-DO gradient control is the key to achieving efficient nitrogen removal.•Simultaneous nitrification & denitrification facilitated in 4 micro-oxygen reactors.•Advanced nitrogen removal efficiency (∼93%) obtained at SW addition ratio of 20%. This study developed an innovative step-feed anaerobic coupled four-stage micro-oxygen gradient aeration process to treat digested swine wastewater. An anaerobic zone was used for prepositive denitrification; four micro-oxygen reactors (zones O1–O4) were used for simultaneous partial nitrification and denitrification through low-dissolved oxygen gradient control, step-feed, and swine wastewater-digested swine wastewater distribution. The nitrogen-removal efficiency was satisfactory (93 ± 3 %; effluent total nitrogen, 53 ± 19 mg/L). Mass balance coupled with quantitative polymerase chain reaction analysis revealed that simultaneous partial nitrification and denitrification was achieved in four micro-oxygen zones. Zones O1 were the major denitrification zones for nitrogen removal; nitrification was primary happened in zones O2 and O3. Correlation analysis confirmed that low-dissolved oxygen gradient control was the key to achieving efficient nitrogen removal. This study provides a low oxygen energy consumption method to treat digested swine wastewater with a low carbon/nitrogen ratio (<3).