Let's first understand ...

Let's first understand desired flow rate.  Then, we might consider a more passive approach: controlled evaporation/condensation.  Use Kenyan heat to evaporate clean (distilled) water from the saline water and collect the evaporate (a simple approach is the use of plastic sheets over the saline water with catch basins along the periphery (image a long tent) for the distilled water).

Just a thought.