Membrane distillation (MD) has shown strong promise for treating hypersaline produced water (PW) streams. Scaling and fouling on the membrane surface, however, have been identified as major challenges for commercialization and widespread application. The focus of this study was to first identify the nature of foulants and scalants on the membrane surface and then investigate the pretreatment strategies that mitigate the extent of fouling and scaling on the membrane surface. Vacuum MD (VMD) was selected for this study because of its higher flux at more moderate feed temperatures that eventually leads better assessment of fouling and scaling on the membrane surface. VMD flux tests were carried out with three different real PW samples at total dissolved solids concentrations in the range of 120–160 g/L. It was found that an efficient pretreatment prior to MD is required to mitigate the fouling potential of the organic matter, mostly suspended constituents, in PW samples. Suspended organics fouled and quickly wetted the MD membrane. Major conventional treatments, including filtration, oxidation, coagulation, air floatation, and aeration were investigated to pretreat the PW before VMD tests. A comprehensive comparative analysis is presented showing that the ultrafiltration and coagulation pretreatments displayed the best performance in mitigating the fouling and scaling, while oxidative pretreatment was found to be effective in reducing the iron concentration to less than 5 ppm. The surface of scaled membranes was carefully characterized to further evaluate the performance of each pretreatment. The components that had the highest tendency to precipitate on the membrane surface were identified as strontium sulfate, calcium carbonate, sodium chloride, iron oxide, and silica. These findings are supported by thermodynamic estimation of the saturation index.

膜蒸馏（MD）在处理高盐度采出水（PW）流方面显示出强大的前景。然而，膜表面上的结垢和结垢已被认为是商业化和广泛应用的主要挑战。这项研究的重点是首先确定膜表面污垢和污垢的性质，然后研究减轻膜表面污垢和结垢程度的预处理策略。选择真空MD（VMD）进行此项研究是因为它在较适度的进料温度下具有较高的通量，最终可以更好地评估膜表面的结垢和结垢。对三种不同的实际PW样品进行了VMD通量测试，总溶解固体浓度在120-160 g / L范围内。发现在MD之前需要进行有效的预处理以减轻PW样品中有机物（大部分为悬浮成分）的结垢潜力。悬浮的有机物结垢并迅速润湿MD膜。在进行VMD测试之前，已对主要的常规处理方法进行了研究，包括过滤，氧化，凝聚，气浮和曝气，以对PW进行预处理。进行了全面的比较分析，结果表明，超滤和混凝预处理在减轻结垢和结垢方面表现出最佳性能，而氧化预处理可有效降低铁浓度至5 ppm以下。仔细表征了结垢膜的表面，以进一步评估每种预处理的性能。在膜表面上具有最高沉淀趋势的组分被鉴定为硫酸锶，碳酸钙，氯化钠，氧化铁和二氧化硅。这些发现得到饱和指数的热力学估算的支持。