中文摘要：

采用聚偏氟乙烯（PVDF）中空纤维疏水膜,利用减压膜蒸馏（VMD）技术,对天津某钢铁厂反渗透（RO）处理后的浓水进行深度浓缩处理,研究了一次絮凝-超滤集成、二次絮凝-超滤集成、分步二次絮凝-超滤集成等预处理方法对RO浓水COD的去除效果,及其对膜蒸馏性能及膜清洗效果的影响,并采用扫描电镜（SEM）和X射线能谱仪（EDS）分析膜表面形貌及污染物组成。结果表明,聚合氯化铝（PAC）絮凝-超滤预处理及PAC絮凝-超滤后再进行阴离子型聚丙烯酸钠（PAAS）二次絮凝-超滤预处理对RO浓水COD的去除效果均能达到40%。在预处理对VMD浓缩过程性能影响的试验研究中表明,经过一次絮凝-超滤集成预处理后,VMD浓缩过程中通量有所提高。浓缩至7～8倍时,较预处理前,通量衰减率降低20%以上。经过PAC絮凝-超滤预处理的RO浓水进行VMD浓缩到约8倍时再进行PAAS二次絮凝-超滤处理后,通量能够提高10%。经过预处理后的废水VMD浓缩过程膜清洗通量恢复效果较无预处理废水好。

英文摘要：

The polyvinylidene fluoride （PVDF） hollow fiber hydrophobic membrane was applied in vacuum membrane distillation （VMD） process for the treatment of reverse osmosis （RO） concentrated wastewater from a steel plant. The effects of pretreatment methods on the COD removal rate containing in the RO concentrated wastewater, on the performance and membrane fouling of VMD process and on membrane rinsing were studied. The morphology and composition of the fouling layer were studied by scanning electron microscope （SEM） and energy dispersive spectroscopy （EDS）, respectively. The reason of the flux declines in VMD process was discussed. The results showed that the COD removal rate reached 40%, and the flux of VMD process was increased after the pretreatments of coagulation and ultrafiltmtion （UF） or two times coagulation and UF. When the concentration factor （CF） reached 8, the flux of VMD process using properly pretreated solution was 20% higher than that using un-pretreated solution as the feed. The flux was increased above 10%, when the feed solution CF got 8 was treated by PAAS coagulation＋UF again. The membrane surface morphology and elemental analysis testified that the fouling of membrane surface was obviously alleviated by pretreatment. The hydrophobic character of PVDF hollow membranes used in VMD process can be easily recovered by chemical rinsing.