Yangkai Liu, Yanxiao Wei, Jingyi Jiang, Min Yang, Jing Chen, Zhenpeng Cao, Risen Yang, Le Luo, Jianhong Jiang, Sanjaya Eli Hendrik, Hong Chen
To enhance the sustainability of wastewater treatment and mitigate water eutrophication, we developed a coupled partial nitritation/anammox (PN/A) and hydroxyapatite (HAP)-induced crystallization system. Conventional chemical crystallization for phosphorus removal relies heavily on reagents, leading to high operating costs. By inducing HAP crystallization biologically, this PN/A-HAP system reduces external chemical demand and lowers operating costs. All experiments used a defined synthetic wastewater at 35 ± 1 °C. The PN/A-HAP system started up in 52 days, reaching 76.0 % total nitrogen and 56.6 % total phosphorus removal at a nitrogen loading rate of 0.9 kg-N/m3/d and an influent phosphorus concentration of 20 mg/L. Candidatus Brocadia enrichment increased from 1.65 % to 8.82 %, while AnAOB activity exceeded 0.6 g-N/g-MLVSS/day, demonstrating the successful initiation of anammox and a consequent reduction in sludge cultivation costs. Sludge morphology changes, Candidatus Brocadia enrichment, and computational fluid dynamics analysis confirmed a sludge recirculation pathway within the reactor. The PN/A-HAP system offers a sustainable, energy-efficient approach to wastewater treatment by integrating partial nitritation/anammox with biologically induced HAP crystallization. This integration shortens start-up, lowers operational costs, and enables resource recovery, thereby providing a valuable reference for future optimization and potential scale-up of single-stage PN/A systems. © 2025 Elsevier Inc.
Key Laboratory of Dongting Lake Aquatic Eco-Environmental Control and Restoration of Hunan Province, School of Hydraulic and Ocean Engineering, Changsha University of Science & Technology, Changsha, 410114, China; RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Kanagawa, Yokohama, 230-0045, Japan; School of Civil and Environmental Engineering, Harbin Institute of Technology (Shenzhen), Shenzhen, 518055, China; China Machinery International Engineering Design & Research Institute Co., Ltd, Changsha, 410007, China; Chemistry Department, Universitas Negeri Malang, 65145, Indonesia
