What does the term 'crossflow' refer to in reverse osmosis?

Crossflow in reverse osmosis refers specifically to the flow of solution parallel to the membrane surface. This mechanism is crucial in minimizing the buildup of concentration polarization and fouling on the membrane. In essence, as water is pushed through the membrane, it helps to sweep away the rejected solutes, promoting greater efficiency in the filtration process. This design allows for a more continuous operation, where some of the flow continues to be processed while concurrently maintaining the performance of the membrane.

In contrast, the flow of solution directly through the membrane pertains to the osmosis process itself, but not to the crossflow concept. The flow moving away from the membrane does not appropriately describe the mechanics of crossflow, and the flow from the membrane to storage does not capture the dynamics occurring during the filtration phase. Therefore, understanding crossflow as a parallel movement enhances the comprehension of optimizing reverse osmosis systems for effective water treatment.