It is that time of year. You must reduce your backwash flow in the Fall or you will find your ion exchange resin in the drain or waste treatment plant.
If the backwash rate for an ion exchange system is set when the water is warm, the flow rate will be too high when the water temperature is cold. Anion resins are more susceptible to this problem because their densities are lower than cation resins. Your ion exchange supplier should have curves of each resin in their literature.
|Example of Backwash Flow Rates and Bed Expansion Chart|
For example, if a water softening system and therefore the tank are designed for a 50% bed expansion at 77F, the backwash flow rate will be about 6.5 gpm/sq ft for Purolite C-100 cation exchange resin. If the temperature of the water decreases to 41F, the bed will expand 120% at that same 6.5 gpm/sq ft sending most of the resin down the drain.
Please note, each resin will have a different backwash rate, so look in the manufacturer's bulletins for the correct value.
Some of the Numerous Flow Controls and Flow Inserts Offered by Res-Kem
|Res-Kem Manufactures Resin Traps for 2", 3" and 4" Piping to Prevent Resin and |
Other Media From Contaminating Downstream Equipment