Optimal design of spacers in reverse osmosis

Spiral-wound membrane (SWM) modules are the most common membrane configuration utilized in reverse osmosis (RO) and nanofiltration. The enhancement of SWM module design, particularly in the geometric design of the feed spacer, can play a crucial role in the cost and the potential for wider application of these modules. The feed spacer influences the flux, pressure losses and fouling in the membrane process and consequently the product water unit cost. Despite the shift in the application of SWM modules of RO toward low salinity sources and the resulting higher sensitivity performance using these waters, the configuration and orientation of feed spacers have not significantly changed since the original design. A wider use of SWM modules, therefore, requires the adaptation of geometric parameters of the feed spacer to the water source. Improving the feed spacer's design according to the feed water type requires the knowledge of previous studies conducted in spacer-filled channels as well as further needed investigations in future. This paper reviews the role of the feed spacer in SWM modules and provides an overview of studies conducted in narrow spacer-filled channels to determine the effect of different geometric characteristics of the feed spacer on hydraulic conditions.