Two-stage sequencing batch reactors with added iron shavings for nutrient removal and aerobic sludge granulation treating real wastewater with low carbon to nitrogen ratios

• DOI: 10.1016/j.biortech.2024.130380
• Publication Date: 2024-01-26T20:44:10Z
• Authors: Zengrui Pan; Hongtang Wei; Chong Qiu; Qianjin Yang; Yifan Liang; Zuchao Huang; Jun Li
• Keywords: Sequencing batch reactor; Granulation; Carbon-to-nitrogen ratio; Autotroph; Carbon fibers

In response to the challenges of limited nutrient removal and the difficulty in forming aerobic granular sludge (AGS) with low carbon to nitrogen (C/N) ratios, a novel two-stage sequencing batch reactors (SBRs) (R1 and R2) system with added iron shavings was proposed and established. The results showed that AGS was developed and nitrogen (82.8 %) and phosphorus (94.7 %) were effectively removed under a C/N ratio at 1.7 ± 0.5. The average size of R1 and R2 increased from 45.3 μm to 138.7 μm and 132.8 μm. Under high biological selective pressure, phosphorus accumulating organisms like Comamonadaceae (14.8 %) and Chitinophagales (5.7 %) experienced enrichment in R1. Furthermore, R2 exhibited an increased abundance of nitrifying bacteria (2.3 %) and a higher proportion of nitrogen removal through autotrophic denitrification (＞17.5 %). Overall, this study introduces an innovative two-stage SBRs with added iron shavings, offering a novel approach for the treatment of low C/N ratios wastewater.