Yangkai Liu, Yanxiao Wei, Zhenpeng Cao, Chengcheng Lin, Jing Chen, Jingyi Jiang, Jiao Jin, Shengbo Gu, Mohd Fadhil Md Din, Sanjaya Eli Hendrik, Zhihua Liu, Hong Chen
The partial nitritation/Anammox-hydroxyapatite (PN/A-HAP) process enables economical nitrogen and phosphorus removal. This study conducted long-term continuous experiments to evaluate the feasibility of the single-stage PN/A-HAP reactor for low-phosphorus wastewater treatment. An equilibrium limitation of the total phosphorus concentration in the effluent (TP-eff) under controlled conditions was identified. With influent NH4+-N at 350 mg/L, hydraulic retention time of 6 h, and calcium to total phosphorus ratio of 4.0, an airlift internal partition bioreactor consistently maintained TP-eff at 2.0 ± 0.3 mg/L in the PN/A-HAP system, even as the total phosphorus concentration in the influent (TP-inf) reduction from 20 to 5 mg/L. This stability results from limitations in phosphorus removal capacity imposed by the saturation index, phosphorus loading rate, and hydroxyapatite crystallization. These findings expand the understanding of the phosphorus removal boundaries and sustainability potential of the PN/A-HAP system, emphasizing advanced post-treatment strategies to further reduce TP-eff. © 2025
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 Transportation, Changsha University of Science and Technology, Changsha, 410114, China; School of Resources and Environment, Hunan University of Technology and Business, Changsha, 410205, China; Centre for Environmental Sustainability and Water Security (IPASA), School of Civil Engineering, Faculty of Engineering, Universiti Teknologi Malaysia, Johor, Skudai, 81310, Malaysia; Chemistry Department, Universitas Negeri Malang, 65145, Indonesia
