Department of Civil and Environmental Engineering, Norwegian University of Science and Technology (NTNU), Trondheim, Norway E-mail:
Department of Chemical Engineering, Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
Water Sci Technol. 2019 May;79(9):1777-1789. doi: 10.2166/wst.2019.178.
The enhanced biological phosphorus removal process makes the phosphorus recovery feasible from the dewatering streams of biological sludge. The physicochemical properties of these sidestreams, as an input to a crystallizer, are different before and after anaerobic digestion. In this study, phosphorus recovery by calcium phosphate is proposed for pre-digestion sidestreams and by struvite precipitation for post-digestion sidestreams. The thermodynamic modeling followed by experimental tests was performed to evaluate the recovery efficiency and product properties of struvite and calcium phosphates. The variations in phosphorus recovery potential, reaction kinetics and particle size distribution emphasize the importance of the adjustment of initial supersaturation and pH of the reaction. The optimum pH, considering the economics and recovery efficiency, for both calcium phosphate and struvite precipitation was found to be pH = 8.5, whereas further increase of pH will not improve the overall efficiency of the process. In the case of calcium phosphate precipitation, it was shown that possible phase transformations should be considered and controlled as they affect both process efficiency and product properties. The economic evaluation indicated that the optimized operational condition should be determined for the phosphorus recovery process and that chemical costs for the production of calcium phosphates is lower than for struvite.
强化生物除磷工艺使得从生物污泥脱水过程中回收磷成为可能。这些侧流的物理化学性质在厌氧消化前后是不同的。在本研究中，提出了通过磷酸钙回收预消化侧流中的磷，通过鸟粪石沉淀回收后消化侧流中的磷。通过热力学模型和实验测试评估了鸟粪石和磷酸钙的回收效率和产物特性。磷回收潜力、反应动力学和颗粒分布的变化强调了调整初始过饱和度和反应 pH 值的重要性。考虑到经济性和回收效率，发现钙磷酸盐和鸟粪石沉淀的最佳 pH 值均为 pH=8.5，而进一步提高 pH 值不会提高整个过程的效率。在磷酸钙沉淀的情况下，表明应考虑并控制可能的相变，因为它们会影响工艺效率和产物特性。经济评估表明，应确定磷回收工艺的优化操作条件，并且生产磷酸钙的化学成本低于鸟粪石。
