If salinity is reasonably ...

If salinity is reasonably consistent and stable then you will select for a halotolerant bacterial population which will deliver the required treatment and you can use a standard wastewater treatment process (just protect from corrosion and size your aeration correctly). However, as Sean Roop says, if your conductivity and salinity swings wildly, you will not get good treatment.

I suggest you check your figures though. I assume you mean chloride and not chlorine? I would have expected that a chloride of 15,000 mg/l (almost seawater) should give you a conductivity of nearer 50,000 uS/cm.