Remove of Salts from Effluent Stream

[MikeHeggie]

I am investigating the removal of salt ions from an effluent stream in order to meet new EPA guidelines. All the experts I have spoken with have suggested that Reverse Osmosis is the only possible method to remove salts and reduce the effluent Electro Conductivity (EC). I have suggested RO to my client however they rejected this idea due to the high construction and operation costs.

Is there an alternative to RO for the removal of salts and reduction of EC?

Logic tells me that there should be a biological or chemical process which will remove this salts, is this not possible?

I will greatly appreciate any advice available.
Thanks
Mike

 

[Jlevie]

Hi Mike,

It will all depend on the type of salts, their concentrations and the levels that you wish to reach. There are a lot of methods to remove salts, but if your client is concerned about cost they may not be terribly happy with any of them.

You can do on-line searches for removal of salts at various web sites,

http://www.che.com

is one that may have a few links, as well as university research pages.

In terms of standard unit ops to remove salts, one can look at precipitation, crystallization (cryogenic or 'seeding' to create supersaturated conditions), some but not all I/X units, RO or NF depending on the salts and concentrations, for some organic salts pervaporation can be an effective but *very* expensive operation (vacuum-based membrane operation, typically used more for specific selectivity of low MW organics in aqueous streams), and for ultra-pure boiler feed and pharmaceutical waters EDI is another pricey option that is on the market.

John