磁粉在磁加载混凝深度除磷中的作用机理分析

为适应天津新地(DB 12/599-2015)对出水总磷的排放需求，对天津某污水处理厂二沉池出水进行磁加载混凝工艺深度除磷实验。探讨了3种磁粉在粒径、表面电荷和磁感应强度等方面对混凝的影响；对比了磁加载混凝和常规混凝在沉降时间、絮体生长动力学的差异；分析了磁加载混凝和常规混凝对于不同形态磷的去除效果。结果表明，在磁加载混凝技术深度除磷中，磁粉的粒径、电性和磁性的协同作用是提高混凝效果的主要因素，粒径范围适中，表面带正电荷，磁感应强度越大越有利于污染物的去除。磁加载混凝技术可减少混凝剂用量、缩短沉降时间、提升去除效果，磁粉在混凝过程中起电性中和、表面吸附、絮凝成核、快速沉降的作用。

Mechanism analysis of magnetic powder function in deep phosphorus removal by magnetic coagulation

In order to meet the total phosphorus discharge demand by the new local standard (DB 12/599-2015) of Tianjin，the magnetic coagulation experiments were conducted to study the deep phosphorus removal from secondary effluent of a local sewage plant. Three kinds of magnetic powders were taken to study the effects of their particle size distribution, surface charge and magnetic induction intensity on coagulation. Then the differences in settling time, floc growth kinetics and removal performance on different phosphorus forms between magnetic coagulation and conventional coagulation were compared. Results show that the synergistic effect of particle size, electrical properties and magnetism of magnetic powder was the main factor to improve phosphorus removal effect of magnetic coagulation, and moderate particle size, positive surface charge and strong magnetic induction intensity were conducive to phosphorus removal. Magnetic coagulation technology can reduce coagulant dosage, shorten settling time and improve removal effect, and magnetic powder plays the roles of charge neutralization, surface adsorption, flocculation and nucleation, rapid sedimentation during the coagulation process.