Problem with split bed DI unit

[redfishblewfish]

This has me absolutely and totally perplexed!!!


I regenerate my DI resin"¦.been doing it for some time. This is not the issue.

The biggest PIA is first separating the two resins to clean them up.


So I was fortunate to come upon an old RO setup with two canisters.

I figured I'd remove the RO membrane and polishing carbon filter and turn it into a DI unit with separate "œbeds""¦"¦.The cationic resin in one, and the anionic resin in the other. This way, when I go to regenerate, no first step of separating the two resins. I purchased two DI canisters from BRS and had plenty of resin to get this thing going.

I will tell you that in the process of taking off the RO stuff, I noticed the two canisters, that are labeled "œIN" and "œOUT," had both "œOUTs" connected. I flipped this one canister around so that the "œOUT" of the first canister entered the "œIN" of the second canister.


So here is my problem"¦.I now have attempted this three times"¦.I can't get down to zero TDS. My most recent attempt was letting the unit run for six hours, and after six hours, I can only match the TDS of the incoming water. The same result for all three separate times I've tried this.

(The number on the left is TDS before the DI resin, the number of the right is after the DI resin.)

Now, I take this same resin and mix it up and put in it a single canister and I'm now back to zero TDS within a minute of starting the water flowing.

What's going on???

 

[redfishblewfish]

So no one has any thoughts on this?

 

[shifty51008]

try switching the resins around, IIRC It makes a diffrence witch resin is 1st

 

[shifty51008]

found it. the cationic resin should be 1st and the anionic resin 2nd

 

[redfishblewfish]

Shifty, thanks for the response. I was aware of the order....as a friend told me about his Kati-Ani unit.....Kati comes first in the name, so cationic comes first. I've been running it with the cationic first, and I'm now temped to switch it around to see what I get.

This is frustrating!!!

 

[shifty51008]

Let me know what you find out as i have always thought about keeping them seperated after recharging but always just remixed it. Would deff save alot of time though not having to seperate them all the time.

 

[SpectraPure]

Separated beds are ok, especially if you are regenerating, but I would consider using a polishing cartridge for your final product water. Also, the Cat-ions will exhaust quicker, and will need to be regenerated more frequently than the Anion. Also, there are many impurities in Cat-ions, and they do have a way of contaminating the An-ion if not processed properly. Thus, your capacity will drop. 0 TDS doesn't mean much to me. DI resins are read in MOHMs. The best DI resins reach 18.3 MOHMs. Separate beds will not stay at 18.3 long, and some separate beds never even make it there. When thousands of dollars are invested into an aquarium why not just buy a good bulk resin that will last hundreds of gallons per cartridge?

 

[pufferpoison]

^ I agree with this. If you have a true 99% rejection rate membrane, your DI should last a long time for a standard 10" fill up and it's somewhere around $10.00 for that refill. It just seems like your spending a dollar to save a dime.

 

[shifty51008]

Its actually much cheaper still to recharge ime. I can recharge enough di to fill 8 canisters for about 15.00

 

[SpectraPure]

Shifty,

The capacity is reduced every time that you regenerate it. Also, every time you regenerate it loses it ability to remove as much. After a longer while, the resin becomes unusable. Also, as I stated before, the cation will exhaust first, because you have it first in order. A split bed will not perform as good as a mixed bed.

Either way, I am very glad that you are saving money, but keep an eye on algae and phosphates.

Jeremy

 

[shifty51008]

I understand completly, thanks for the info. I will prob get a hold of you guys later on finding ways to improve my unit though.

 

[SpectraPure]

Correction. The Anion will exhaust quicker than the Cation. My apologies. It was late last night.

Have a wonderful day!

Shifty,

We will be here when you need us.

=)

 

[Emmanuel75]

found it. the cationic resin should be 1st and the anionic resin 2nd

Thanks for this! This solved my problem!