Sodium Reduction in Process Feed Water

[LWalke]

I have a process that is somewhat sensitive to sodium. The level in the feedwater must be reduced from 100ppm to 30ppm. The required feedrate is not that high - only around 1000 gallons per day. Hence, batch or continuous treatment is suitable...obviously, coninuous would be nice but cost is a major consideration.

Does anyone know of a relatively cheap way to do this? An ion exchange approach is probably preferred. Again, dumping a chemical into the water and stirring it out in a tank for a couple of hours and pumping through a polishing filter would be a perfectly suitable approach. The question is what chemical is best for this and easily obtained at a reasonable cost?

The sodium in the water is in the form of sodium chloride and sodium sulphate.

Reverse osmosis has been recommended and that is an option. However, I find it hard to believe that other, less costly solutions are not available.

Thank you very much for any suggestions.

 

[bimr]

The most cost effective method at the present time is RO. The RO process will typically reject 90% of the sodium.

Ion exchange is the second most cost effective method.

There are no other options.

 

[moltenmetal]

Ion exchange is the way to go. RO will cost less to operate if you can afford to waste a fair bit of water.

 

[LWalke]

Thank you for the information.

Any details on the preferred ion exchange reaction?

 

[moltenmetal]

Buy two cartridge-type ion exchange beds. Put them in series. Pump the water through at the manufacturer's recommended rate, into the receiver tank, once through rather than pump-around. Sample and analyze between cartridges. Replace or regenerate the first one when the ion you're worried about breaks through.

 

[bimr]

Ion exchange is a non-selective process that will remove essentially all of the sodium. The preferred resin mixture is known as mixed bed resin.

Many of these resin cartridge systems are color metric to show the user when the cartridge is exhausted.

If money is tight and you are that interested in low cost solutions, you can bypass 30% of the flow around the ion exchange cartridge and still get 30 mg/l sodium. 30% X 100 mg/l + 70% X 100 mg/l = 30 mg/l

You can also call a firm such as a Culligan and get a service exchange unit that Culligan will change on a periodic basis. You can probably arrange for a $/1000 gallon cost arrangement.