Revision history [back]
Just to add TDS is by definition dissolved and capable of passing through a 2 micron filter. Pretty much anything that will go through a 2 micron filter will go straight through a slow sand filter too, so I wouldn't bank on any decrease in TDS with slow sand or bone char.
You generally need desalination for TDS removal. Blending with a low TDS source may be more economical if one is available.