Optimization of up-flow velocity enhances the performance of partial denitrification/anammox process in expanded granular sludge bed reactor based on the formation of hydroxyapatite

作者：Shenghao Ji, Shen Cui, Hongjun Zhao, Haojie Qin, Yu Qin, Yujie Chen, Yu‐You Li · 发表于：Chemical Engineering Journal · 年份：2025 · DOI：10.1016/j.cej.2025.166927 · 被引用次数：7 · 研究领域：Wastewater Treatment and Nitrogen Removal

Partial denitrification/anammox (PDA) offers an effective strategy for deep nitrogen removal from effluents following the anaerobic ammonium oxidation (anammox) treatment of high-ammonium wastewater. However, the poor settleability of PDA sludge limit reactor performance and hinder the application of mass transfer enhancement measures such as increased up-flow velocity. In this study, hydroxyapatite (HAP) was introduced to promote sludge settleability and enabling stable operation at high up-flow velocities. A high nitrogen loading rate (NLR) of 4.11 g N/L/d was successfully achieved at an up-flow velocity of 3.78 m/h. The presence of HAP ensured that the upper sludge, which typically exhibited weaker settling performance, maintained excellent settleability (>40 m/h), thereby enabling the use of high up-flow velocity. Under enhanced mass transfer conditions, the partial denitrification/anammox-hydroxyapatite (PDA-HAP) reactor achieved a total nitrogen removal efficiency (TNRE) of 89.2 % and an anammox contribution efficiency (ACE) of 80.1 % during high-load operation. Functional differentiation across the reactor zones enabled the effective integration of partial denitrification and anammox functionalities, allowing each to exhibit optimal activity in its respective zones (0.23 ± 0.03 g N/g VSS/d and 0.15 ± 0.01 g N/g VSS/d, respectively). This study presents a viable strategy for improving PDA performance, supporting the broader implementation of anammox-based technologies f...