In the event that you need to bond to the masonry with conventional mortar or grout after application of paraffin wax, it will be necessary to remove the wax. The wax needs to be vaporized. This could be done at lower temperatures in a lab with application of low pressure (vacuum). In an outdoor setting the best method may be to build a charcoal fire and slowly increase the oxygen supply from a metal pipe and a blower or compressor after the interior of the tank exceeds the melting point of the paraffin on all surfaces. Apply heat until no more smoke/vapor is being released. Allow to cool slowly without any water. Masonry can tolerate heat to 300C (572F) without damage and 500C (932F) before destruction is likely. Paraffin wax boils/vaporizes at 370C (698F). I suspect you will get ignition at much lower temperatures than that so basically, burn it out and limit the oxygen to keep the temperature down.
Bob Campbell said:
Just remember, once you paint with epoxy or seal with paraffin you have placed a substance on the tank that will not readily adherer to more mortar or Thoroseal. I had no problems and did nothing more than rinse. I suggest rinsing and following the directions from Thoroseal. Then test the water and determine if further action is required before committing to a second layer.