DAF Selection Criteria in SWRO Plants

Dear All,

When is it necessary to install a dissolved air flotation (DAF) system in seawater reverse osmosis (SWRO) systems? From my point of view the following parameters are critical: TSS, Turbidity, SDI, DOC and TOC. 

So the question would be which is the value of each parameter, that makes DAF system mandatory? My understanding is that with a Turbidity higher than 30 NTU, DAF is necessary.

Has anyone other guidelines or experiences?