Abstract: Different seawater pretreatment processes were studied in terms of comparative analysis of turbidity, chemical oxygen demand (COD_Mn), pollution density index (SDI₁₅), etc and the effects on ultrafiltration membrane flux of different pretreatment processes. Coagulation-sedimentation or air flotation process can reduce seawater turbidity effectively. With sand filtration or fibre filtration, turbidity can be reduced to around 0.3NTU. When seawater was treated by the ultrafiltration, regardless of the method, the turbidity of the water and SDI₁₅ can meet the requirement of reverse osmosis. When ultrafiltration is adopted directly, the removal effect of COD_Mn was very bad. When ultrafiltration combines with coagulation-sedimentation or air flotation, the removal rate of COD_Mn was enhanced. Pretreament methods have a great influence on ultrafiltration membrane flux. Ultrafiltration membrane flux declined rapidly by ultrafiltration directly. Membrane flux attenuation slows by coagulation-sedimentation or air flotation. Membrane flux attenuation was well controlled after sand filtration or fibre filtration. Membrane flux attenuation is lowest by using coagulation-sedimentation/ fibre filtration.

Key words: reverse osmosis pretreatment, coagulation-sedimentation, air flotation, sand filtration, fibre filtration, ultrafiltration

摘要： 对不同海水预处理工艺进行了研究，对比分析了不同工艺产水浊度、化学需氧量（COD_Mn）、污染密度指数（SDI₁₅）等参数及不同预处理工艺对超滤膜膜比通量的影响。混凝-沉淀或气浮处理能够有效降低海水浊度，配合砂滤或纤维过滤，浊度可以降低到0.3NTU左右。当超滤处理海水时，无论采用何种预处理方法，其产水浊度和SDI₁₅都可以满足反渗透进水要求。直接超滤时，COD_Mn去除效果较差，超滤结合混凝-沉淀或气浮处理时，COD_Mn去除率有了较大的提高。预处理方法对超滤膜膜比通量影响较大，直接采用超滤进行处理时，超滤膜膜比通量衰减较快，经混凝-沉淀或气浮处理后，膜比通量衰减有所减缓，进一步经砂滤或纤维过滤后，膜比通量的衰减得到了较好的控制。采用混凝-沉淀/纤维过滤预处理工艺时超滤膜膜比通量衰减最低。

关键词: 反渗透预处理, 混凝-沉淀, 气浮, 砂滤, 纤维过滤, 超滤