This study evaluates various options for full-scale modular configuration of forward osmosis (FO) process for osmotic dilution of seawater using wastewater for simultaneous desalination and water reuse through FO-reverse osmosis (RO) hybrid system. Empirical relationship obtained from one FO membrane element operation was used to simulate the operational performances of different FO module configurations. The main limiting criteria for module operation is to always maintain the feed pressure higher than the draw pressure throughout the housing module for safe operation without affecting membrane integrity. Experimental studies under the conditions tested in this study show that a single membrane housing cannot accommodate more than four elements as the draw pressure exceeds the feed pressure. This then indicates that a single stage housing with eight elements is not likely to be practical for safe FO operation. Hence, six different FO modular configurations were proposed and simulated. A two-stage FO configuration with multiple housings (in parallel) in the second stage using same or larger spacer thickness reduces draw pressure build-up as the draw flow rates are reduced to half in the second stage thereby allowing more than four elements in the second stage housing. The loss of feed pressure (pressure drop) and osmotic driving force in the second stage are compensated by operating under the pressure assisted osmosis (PAO) mode, which helps enhance permeate flux and maintains positive pressure differences between the feed and draw chamber. The PAO energy penalty is compensated by enhanced permeate throughput, reduced membrane area, and plant footprint. The contribution of FO/PAO to total energy consumption was not significant compared to post RO desalination (90%) indicating that the proposed two-stage FO modular configuration is one way of making the FO full-scale operation practical for FO-RO hybrid system.

中文翻译：

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通过正向渗透和反渗透混合系统对海水进行渗透稀释的正向渗透膜模块化结构

这项研究评估了正向渗透（FO）工艺的完整模块配置的各种选项，这些正渗透用于利用海水进行海水的渗透稀释，同时通过FO-反渗透（RO）混合系统进行脱盐和水回用。从一个FO膜元件操作获得的经验关系用于模拟不同FO模块配置的操作性能。模块操作的主要限制标准是始终保持进料压力高于整个外壳模块的进料压力，以确保安全操作而不影响膜的完整性。在此研究中测试的条件下进行的实验研究表明，当拉伸压力超过进料压力时，单个膜壳不能容纳四个以上的元件。然后，这表明具有8个元件的单级壳体对于安全的FO操作不太可能实用。因此，提出并仿真了六个不同的FO模块化配置。两阶段FO配置在第二阶段使用多个相同或更大的垫片厚度（并联）的多个壳体，可减少拉拔压力的积累，因为在第二阶段将拉拔流速降低到一半，从而允许在第二个阶段中使用四个以上的元件第二阶段的住房。通过在压力辅助渗透（PAO）模式下进行操作，可以补偿第二阶段的进料压力损失（压降）和渗透驱动力，这有助于提高渗透通量并维持进料室和汲取室之间的正压差。PAO能量损失可通过提高渗透量，减少膜面积来补偿，和工厂的足迹。与后海水淡化后（90％）相比，FO / PAO对总能耗的贡献不显着，这表明拟议的两阶段FO模块化配置是使FO-RO混合系统实际运行FO的一种方法。