Lab-scale autothermal thermophilic aerobic digestion can maintain and remove nitrogen by controlling shear stress and oxygen supply system

• Published in: Journal of bioscience and bioengineering Vol. 132; no. 3; pp. 293 - 301
• Main Authors: Zhang, Min, Tashiro, Yukihiro, Asakura, Yuya, Ishida, Natsumi, Watanabe, Kota, Yue, Siyuan, Akiko, Maruyama-Nakashita, Sakai, Kenji
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2021
• Subjects: Autothermal thermophilic aerobic digestion; Bacterial community structure; Gas-inducing/disk-turbine agitator; Nitrogen maintenance/removal; Physicochemical property; Shear stress; Shear stress; Autothermal thermophilic aerobic digestion; Nitrogen maintenance/removal; Gas-inducing/disk-turbine agitator; Bacterial community structure; Physicochemical property
• ISSN: 1389-1723; 1347-4421
• DOI: 10.1016/j.jbiosc.2021.05.008

Autothermal thermophilic aerobic digestion (ATAD) is used to treat human excreta hygienically. We previously reported a unique full-scale ATAD, showing distinctive bacterial community transitions and producing high-nitrogen-content liquid fertilizer; nevertheless, the mechanism remains unclear. One hypothesis involves using a gas-inducing (GI) agitator. We designed a lab-scale GI system and compared it with a disk-turbine (DT) agitator system by mimicking the temperature shift of full-scale ATAD. The agitation system and its agitation speed greatly affected physicochemical properties and bacterial community structure. GI system at 1000 rpm (GI1000; high total carbon removal efficiency, 88.3%), with few nitrifying and denitrifying bacteria, maintained a high ammoniacal nitrogen concentration and had more shared operational taxonomic units related to Acinetobacter sp., Arcobacter sp., and Longimicrobium sp. with the full-scale ATAD compared with the GI system at 490 rpm and DT system at 1000 rpm (DT1000). Furthermore, DT1000, with a high abundance of nitrifying and denitrifying bacteria such as Alcaligenes aquatilis and Pseudomonas caeni, removed 94.7% total nitrogen with 71.9% total carbon removal efficiency. These results suggested that shear stress and oxygen supply system would change the bacterial community structure, thus affected ATAD performances. Consequently, it is possible that ATAD can be applied for not only production of highly nitrogen-containing liquid fertilizer but also extremely nitrogen removal of wastewater. •A gas-inducing lab-scale ATAD mimic the unique features of the full-scale ATAD.•Shear force and oxygen supply system would affect ATAD performances drastically.•GI1000 had more similar bacterial community to full-scale system than DT1000.•Nitrogen maintenance and removal occurred in GI1000 and DT1000, respectively.•ATAD can be applied for nitrogen-fertilizer production and nitrogen-removal process.