CO2 is difficult for both RO and EDI to remove since it has no charge, or is weakly ionized. It is important to remove CO2 in the EDI pretreatment because it will lower the EDI product water quality, will compete with silica for removal, and may lead to scaling of the EDI.
Here are 3 ways to remove CO2 effectively in a system:
- Corosex II absorbant media, prior to the RO
Benefits: Passive and chemical-free
Disadvantage: increases scaling potential
- Raise pH before the RO to 8.3 (or before 2nd pass RO)
Benefit: Makes RO highly effective
Disadvantage: Uses chemicals (NaOH)
- Use GTM (Liqui-Cel®) after the RO
Benefit: Highly effective and chemical-free
Since EDI concentrate scaling is caused by the combination of 3 things: 1) Ca/Mg hardness ions, 2) CO2, and 3) high pH, scaling is prevented by removing CO2, and with SnowPure's non-scaling 'Thin Concentrate' design which also lowers the pH of the concentrate.