UF followed by RO I 100% ...

UF followed by RO

I 100% agree with Mr.Murali Kochukrishnan that UF followed by RO is the best option to treat TDS.  There are ways of decreasing the cost of RO treatment as well.  For example, you could treat all of the raw water with the UF membranes to remove suspended solids and some microbiology.  A RO could be used treat a slip-stream of the UF permeate.  The RO permeate could then be blended back with the remainder of the UF permeate to create a lower TDS water.  However, a chemical characterization should be performed on the raw water and treated waters to ensure that the ionic constituents in the final water are within safe ranges.  For example, sulfate is a constituent of the TDS.  If sulfate in the final water is above 600 ppm, it can have laxative effects on infants.  I also recommend that the water then be disinfected (chlorine, ozone, UV, etc).