[curiouscat]

I read of an idea recently that I'm somewhat skeptical about but wanted to put it out there for comments.

Effluents often have high contents of dissolved solids, and to reduce TDS (Total Dissolved Solids)  I read a proposal where a company intends to precipitate said salts out with a solvent. The idea being that the presence of a miscible solvent would reduce the solubility of the dissolved salt sufficiently to precipitate it.

As an example, say you had a 10% NaCl solution as an aq. effluent stream. Could you add enough methanol to precipitate a part of it out? Then, of course, you'd still have to distill off a substantial part of the MeOH and reuse it. Probably via distillation.

Conventional competition might be a multi effect evaporator. One selling point I might think of is that it'd cost a lot less steam to distill off a well chosen solvent as opposed to evaporating high latent heat water from  a salt solution. OTOH, any solvent losses are probably going to be a killer.

Both approaches would need something like a centrifuge to separate the solids. 

Any comments? Has potential or a dud? Would some other solvent make more sense?