Efficient and stable removal of organic matter, nitrogen and phosphorus from swine manure digestate by coupling high-rate activated sludge and single-stage partial nitritation/anammox-hydroxyapatite processes
Yunzhi Qian, Shilong He, Yan Guo, Fuqiang Chen, Junhao Shen, Yu Qin, Yu‐You Li
Abstract
Organic matter stress restricts the efficiency and broader applicability of anammox process for high-nutrient digestate treatment. A high-rate activated sludge (HRAS) process coupled a single-stage partial nitritation/anammox-hydroxyapatite (PN/A-HAP) process was developed to treat swine manure digestate. The coupled processes achieved stable removal efficiencies of 92 % (N), 63 % (P), and 66 % (chemical oxygen demand, COD), respectively. The HRAS process reduced the five-day biological oxygen demand/COD ratio to 0.31, effectively mitigating the organic stress of anammox process. The synergistic effect of HAP crystallization and external forces induced structural fragmentation of PN/A-HAP granules. The HAP microcrystals in fragmented sludge (<100 μm) function as nucleation cores, driving PN/A-HAP granules reformation. Ca. Kuenenia dominated in the PN/A-HAP microbial community and demonstrated a positive correlation with the saturation index of HAP. This study offers a significant reference for the implementation of the HRAS-PN/A HAP process aimed at achieving COD, N, and P removal.