Ferric salt was used as precipitator for phosphorus removal from supernatant of a SBR at anaerobic stage to recovery phosphorus source. To reduce adverse effect of chemical residue on the microorganism and reclaim phosphorus resources as much as possible, Box-Benhnken center combination experimental principle and response surface methodology were adopted, rations of dosage of ferric salt to that of phosphate, agitation speed, flocculation reaction time were chosen as independent variable and residual ferric ion concentration for response value to explore the interaction among those parameters in this study. With the aid of Design-Expert 8.0 software, a quadratic curved surface model was obtained. The result showed that the optimum conditions to be a dose of 1.40:1molar ratio of ferric ion to phosphate, stirring intensity for 275r/min with 30s in coagulation and 60r/min with 18min in flocculation, and precipitation time of 20min. The residual iron ion concentration could be kept at 0.37mg/L, and the efficiency of phosphorus removal could be achieved more than 97.66%.%在用铁盐对厌氧段富磷上清液进行化学磷沉淀以实现磷的回收和达标排放的 SBR 系统中,为了减少铁盐化学除磷残余物可能对生物处理系统的影响,采用Box-Benhnken中心组合试验原理和响应面分析法,选择Fe：P、混凝搅拌强度、絮凝搅拌强度、搅拌时间等为自变量,残余铁离子为响应值,研究自变量之间的交互作用,以期优化化学除磷条件.通过Design-Expert 8.0软件得到1个二次响应曲面模型.得出最佳除磷条件：Fe：P比为1.40：1,搅拌强度为275r/min,快速搅拌时间为30s,絮凝搅拌强度为60r/min,絮凝时间为18min,沉淀时间为20min.在此条件下,化学混凝后残余铁离子浓度为0.37mg/L,化学除磷率大于97.66%.
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