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Phosphorus (P) removal still faces challenges in eutrophic water treatment. Combining adsorption and biological reaction can efficiently reduce the P concentrations, achieving long-term function. In this study, five kinds of pellets were produced using cement, bentonite, and organic carbon (rice husk powder) with mass ratios of 100%:0%:0% (M1), 95%:5%:0% (M2), 92.5%:5%:2.5% (M3), 90%:5%:5% (M4), and 85%:5%:10% (M5) for phosphorus removal in eutrophic water. The static adsorption experiment revealed that both Langmuir and Freundlich models were suitable for describing the adsorption characteristics. The P-bonding energy (KL) and adsorption capacity (K) followed the order of M1 < M2 < M3 < M4 < M5. The adsorption processes conformed to the Pseudo-second-order kinetic model. The adsorption capability of pellets decreased with increasing pH levels. The Cl−, NO3−, and SO42− showed negligible effects on adsorption, while CO32− reduced the adsorption amount. In the dynamic experiment, all the pellets have sustained P removal efficiency with the average removal rates of 58.54% (M1), 60.78% (M2), 63.97% (M3), 66.81% (M4), and 72.05% (M5). The presence of CaHPO4·2H2O in pellets after P removal indicated phosphate precipitation and ion exchange. The attached microbes in pellets exhibited an increase in Proteobacteria abundance contributed to biological phosphorus removal and long-term effectiveness. Hence, this study introduces innovative cement-based pellets for phosphorus removal in eutrophic water, establishing a possibility for practical applications.
Zhang et al. (2024) studied this question.