Nutrient removal and phosphorus recovery performances of a novel anaerobic-anoxic/nitrifying/induced crystallization process

An anaerobic-anoxic/nitrifying (A2N) two sludge process coupled with induced crystallization (IC) called A2N-IC process was developed for wastewater nutrient removal and phosphorus recovery. The performances of A2N-IC process in comparison with A2N process at different COD to phosphorus (COD/P) feeding ratios were investigated. The results indicated that A2N-IC achieved not only high and stable nutrient removal but also phosphorus recovery. Calcium phosphorus crystals were formed in the crystallization reactor in A2N-IC. Moreover, the incorporation of chemical induced crystallization improved biological phosphorus removal. In A2N-IC process, phosphorus removal efficiency was consistently maintained at 99.2%, whereas in A2N it decreased from 93.0% to 65.7% with the decrease of feeding COD/P ratio. The COD and ammonia removal efficiencies were regardless of feeding COD/P ratio in the two processes.