Hi Henrique,  this is our ...

Hi Henrique,  this is our very old experience, but you may find something of use from it.  We ran a SWRO pilot facility on the coast of Namibia in the early 1980s.  Drawing sea water from the very organically rich Benguella Current of the Atlantic Ocean coming up from Antartica. We struggled a lot initially trying to achieve an acceptable SDI to put the water onto the RO membranes.  We then (by accident) found that if we stored the water chlorinated in open ponds for 48 hours we were able to achieve good SDI results using conventional treatment (coagulation, flocculation and diatomaceous earth cartridge filtration).  At that time we put the improvement down to UV oxidation linked to the chlorination and exposure to the sunlight.  Today you can probably achieve the same effect using advanced oxidation techniques (UV with ozone or hydrogen peroxide).  

When the full scale plant was constructed some years later, they chose UF/RO configuration.