I would suggest a ...

I would suggest a conventional method: 

1. Place the sludge in a chamber in which stirring can be done.
2. Add some water and stir to obtain slurry.
3. Add calcium chloride and stir for while. Allow calcium sulphate to settle as precipitate.
4. remove calcium sulphate as sludge is removed or decant the supernatant now rich in sodium chloride.
5. The sludge (gypsum) can be used as soil conditioner and solar salt can be obtained from supernatant by solar evaporation. The salt can be used in preparation of animal feed if no toxic matter is present.
6. Since the end products will be utilisable, the scheme may be financially viable.