Evaluating the overall performance of immobilized particles through different crosslinking strategies and their nitrification characteristics

Abstract

In the activated sludge process, ammonia-oxidizing bacteria (AOB) grow slowly and have poor adaptability to adverse environments. Immobilization technology is an important means to improve AOB retention capacity. In this study, the strength, stability, and biological activity of different immobilized particles (PVA–SA (B), PVA–SA (S), PVA–SA (P), and PVA–SA (N)) were studied. In the short-term experiments, PVA–SA (S) and PVA–SA (N) particles exhibited good performance. The chemical oxygen demands (COD) (48 h) of PVA–SA (B), PVA–SA (S), PVA–SA (P), and PVA–SA (N) particles were 69.8, 52.6, 54.2, and 48.4 mg COD/g particles, respectively. Moreover, the specific oxygen uptake rate (SOUR) values were 11.1, 9.6, 3.5, and 8.0 mg O₂/(g MLSS h), respectively. In the long-term experiment, the PVA–SA (S) and PVA–SA (N) nitrification reactors were operated. The influent NH₄⁺–N concentration gradually increased from 10 to 80 mg L⁻¹. After 40 days, the NH₄⁺–N removal efficiencies of PVA–SA (S) and PVA–SA (N) reactors reached 95%. Meanwhile, the intact ratios of PVA–SA (S) and PVA–SA (N) particles were 100% and 67.1%, respectively. The PVA–SA (S) particles were considered as the most promising immobilized particles in engineering applications.