We have high TDS in much of ...

We have high TDS in much of our groundwater here in Saskatchewan, Canada and the most effective option that is guaranteed to remove TDS is nano filtration.  We have tried traditional methods but in the end, nano filtration will drop your TDS to nearly 5 ppm or lower every time.  Mind you, we usually have a pre-treatment process upfront depending on the water source.  For example if the water source is groundwater we have a Manganese Greensand filter in front of the NF filters and in front of the NF filter right before the high pressure pumps we always install 5 micron filters to capture any large particles that somehow found their way through.  And of course we install an ORP sensor to make sure that KMnO4 from the Greensand filters does not enter the NF filters....it is very complicated process and I can go into much more detail if you wish.  And if the water source is surface water the pre-treatment that I choose is dependant on the water chemistry and again if you want more details please let me know as my response will be very long otherwise.