Membrane fouling is a major challenge for membrane-based wastewater treatment. In this study, we investigated the integrated forward osmosis-membrane distillation (FO-MD) process for landfill leachate treatment. However, severe scaling induced by the formation of calcium sulfate happened at the FO membrane selective layer. Herein, an organic phosphonic acid scale inhibitor, hexamethylene diamine tetra (methylene phosphonic acid) (HDTMPA), was added in draw solution (DS) to control the scaling behavior. HDTMPA chelated with Ca²⁺ to prevented the nucleation and growth of gypsum scale crystals and alleviated membrane scaling. For FO membrane cleaning, the water flux recovery rate was greater than 90% after three scaling-cleaning cycles owing to the formation of deformed crystals and loose scaling layer via addition of HDTMPA. The mechanism of scaling with the existence of HDTMPA were further explored. In addition, we conducted long-term FO-MD experiment using NaCl DS with HDTMPA. The efficiency of the integrated system was much superior to that of the FO alone system with an extreme high contaminant rejection of 99%. HDTMPA not only alleviated FO scaling, but also prevented wetting of the MD membrane, and then promoted the efficiency and operation stability of the integrated FO-MD system.

膜污染是基于膜的废水处理的主要挑战。在这项研究中，我们研究了用于垃圾渗滤液处理的集成正向渗透膜蒸馏 (FO-MD) 工艺。然而，由硫酸钙的形成引起的严重结垢发生在 FO 膜选择层。在此，将有机膦酸阻垢剂六亚甲基二胺四（亚甲基膦酸）（HDTMPA）添加到汲取溶液（DS）中以控制结垢行为。与 Ca ²⁺螯合的 HDTMPA防止石膏鳞片晶体的成核和生长，减轻膜结垢。对于FO膜清洗，由于加入HDTMPA会形成变形晶体和松散的结垢层，经过三个结垢-清洗循环后，水通量恢复率大于90%。进一步探索了随着 HDTMPA 的存在而缩放的机制。此外，我们使用 NaCl DS 和 HDTMPA 进行了长期 FO-MD 实验。集成系统的效率远远优于单独使用 FO 系统的效率，具有 99% 的极高污染物去除率。HDTMPA 不仅缓解了 FO 结垢，还防止了 MD 膜的润湿，进而提高了集成 FO-MD 系统的效率和运行稳定性。