Organics scavenging resin used
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Purolite A860.
Purolite A502PS (Nitrate scavenger but also organics scavenger).
Regeneration of the A860:
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10% NaCl + 2% NaOH.
Best at 45-50C + constant stirring.
During regeneration the resin exchanges the absorbed organics with Cl atoms.
500 gph pump is used to circulate the brine/NaOH through the dirty A860.
The regeneration is done in the reactor. But the reactor must have fine screens or the grains will flow out.
Regenerating by pouring out the resin and stirring on a hot plate works very well but it’s too involved.
Circulate in backwash direction without removing the resin from the reactor. Mix the brine with hot water. Takes 1-2 hrs each cycle, can do 1 or 2 cycles changing the brine in between, brine volume is 2.5 gals for 1 cycle (Andrew).
Why deionize the aquarium water?
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When in the aquarium the Cl from the resin goes into the water during the organics/Cl exchange that the resin is designed for. The Cl accumulates over time (discus live in TDS 30-50 ppm water but the Cl can creep up to 120+ ppm over time (Andrew)). So removal of the Cl from the tank water is a must.
How to remove the Cl (water change vs. deionization)
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1. Smaller tanks – Cl removal from the water is done done with water change.
2. Larger tanks – large volume water changes are needed so it is more practical to deionize the water to remove Cl.
Does the DI remove other (needed) ions?
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Yes, DI resins remove Cl but also other ions – so remineralization is needed.
Remineralization is not excessive (from practical experience, Andrew).
The deionization equipment and process
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The deionization is done with separate Cation and Anion DI resins.
Using two 20″ x 4.5″ drop filter housings.
10″ housings can not be used – not enough area, outflow is a trickle (Andrew)
Color changing DI resins (cat and anion) are used inside a 20″ x 4.5″ clear refillable cartridge that fits inside the 20″ housing. Clear housing + cartridge + color changing DI resins allow to see when the DI resin is depleted.
IMPORTANT:
1. Cat must be BEFORE anion!
2. No CO2 in the incoming water! Run the DI after shutting off the CO2 and allowing some time for it to dissipate from the tank water. CO2 forms ions in the water and they are scavenged by the DI resin like any other ion – the CO2 uses up exchange sites on the resin and has no benefit from being sequestered.
Flow rate
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Pump that is rated 3,400 gph (Eheim 1262).
The water is taken from the sump (Andrew).
The outflow from the second of the two 20″ housings is approx. 500 gph outflow (Andrew).
Deionization efficiency
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In 400 gals tank TDS 110 went down to 25-27 in about 2.5 hrs. (Andrew).
The following are links to sellers of everything needed. These links will get obsolete at some point.
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DI resin recharge
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Cation – with HCl
Anion – with NaOH
Recharging will not make the color revert to the color of fresh DI resin – the color change when the resin is saturated is lost.
Anion resin:
https://airwaterice.com/collections/di-deionization/products/anion-di-resin-color-changing-bulk-media?_pos=14&_fid=1c953db41&_ss=c
Clear refillable cartridge – 20×4.5 x 2
https://www.freshwatersystems.com/products/20-x-4-5-clear-empty-refillable-water-filter-cartridge?variant=31454148689995&c1=GAW_SE_NW&source=PLA_USA_PM_TOP&cr2=pmax__-nw-__shopping_top_products&kw=31454148689995&cr5=pla&cr7=c&hsa_grp=&hsa_ad=&hsa_tgt=&hsa_kw=&hsa_mt=&gad_campaignid=22253574867
Clear water filter housing – 20×4.5 x 2
https://www.walmart.com/ip/20-Transparent-Big-Blue-Housing-for-Whole-House-Water-Filtration-System-1-Brass-Port-Mounting-Hardware/647080695?wmlspartner=wlpa&selectedSellerId=16704
Pump 3400 lph
https://www.saltwateraquarium.com/universal-pump-1262-3400-eheim/
Camino Real, 1975 