Fig. 3: The poor performance of limestone dosing and mechanism elucidation.

a Images of limestone-treated WAC wastewater. The P removal efficiency (b) and Ca concentration (c) right after mixing and post-settling under increasing Ca/P dosing ratios in limestone dosing. d The XRD patterns of the ground dried products from various Ca/P dosing ratios in limestone dosing. e Schematic diagram of the Ca-phosphate crystallization and redissolution in limestone precipitation. Data with error bars represented as mean ± s.d. (n = 3).