What is the flow rate? Is it ...

What is the flow rate? Is it a small stream or not? If it is not too big, then there could be solutions that can address the COD & conductivity simultaneously,, but if it is a big flow rate, then you are going to need a dedicated upfront biological process (preferentially anaerobic) to address the very high COD as it will be too expensive for the system that I have in mind. The anaerobic process will most probably have to be followed by an aerobic polishing step before you can even start considering to filter and feed a BWRO plant that will remove the dissolved salts.

In closing, do you have a better water quality?