Process optimization of anammox-driven hydroxyapatite crystallization for simultaneous nitrogen removal and phosphorus recovery.

Based on the requirements for advanced treatment and resource recovery of nitrogen and phosphorus pollutants in wastewater, the coupled anammox and hydroxyapatite crystallization (anammox-HAP) process was studied with an aim of achieving high efficiency and low energy consumption during simultaneous nitrogen and phosphorus removal. In the long-term experiments and batch tests, the effects of substrate conditions (nitrogen and phosphorus load, calcium concentration, etc.) on the nitrogen removal and phosphorus recovery efficiencies were investigated. The granular structure and crystal properties were analyzed together with microscopic characterization methods, and the formation mechanism of coupled anammox-HAP granules was verified. Based on these experiments, a theoretical model and technical method for realizing the coupled process were established, and a reference for practical engineering application was provided.