↓ design variants Ι process description Ι examples of use Ι technical data Ι cost of operation Ι further information
In a softening plant, alkaline earths dissolved within the water will be exchanged with neutral salts via ion exchange. Regeneration is conducted with common salt dilution, once the ion exchange resin has been depleted.
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| Picture: Softener, designed as duplex plant with diaphragm valves, brine dissolving tank. |
During the softening process, alkaline earth ions like calcium (Ca2+) or magnesium (Mg2+) are exchanged for sodium ions (Na+) at the ion exchange resin. For this purpose, the to be softened water flows through the resin bed inside the softening vessel. The actual ion exchange occurs for example according to the formula:
Ca(HCO3)2 + Na2 [resin] → Ca [resin] + 2NaHCO3
MgSO4 + Na2 [resin] → Mg [resin] + Na2SO4
The sodium ions remain within the soft water, for example as sodium bicarbonate (NaHCO3) or sodium sulphate (Na2SO4). Thus, the salt content of the water does not change due to softening. The concentration of alkaline earths can be reduced to < 0.01 mmol/l, which approximately equals a total hardness of < 0.05 °dH.
Once the ion exchange resin is depleted, it needs to be regenerated with common salt (NaCl). This does for example occur according to the formula:
Ca [resin] + 2NaCl → Na2 [resin] + CaCl2
The regeneration effluent, which includes the calcium chloride (CaCl2) and magnesium chloride (MgCl2) formed during the regeneration process, as well as surplus sodium chloride, can be discharged into the sewer system.
Regeneration is triggered and executed fully automated. Depending upon the plant size either quantity-dependant or quality-dependant, by measuring the hardness remaining in the soft water.
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| Picture: Softening plant, flow capacity 8 m³/h, commissioned 2005 in Zörbig, Germany. |
(varies depending upon design and operating conditions)
| flow rate: | 0.5 ... 200 m³/h |
| raw water pre-pressure, abs: | 2 ... 10 bar |
| raw water temperature |
8 ... 50 °C up to 120 °C for special applications |
| raw water quality: |
pre-filtrated well or surface water town water permeate condensate |
| service life: | 6 ... 24 h |
| regeneration agent: | common salt (NaCl) |
| soft water quality: |
total alkaline earths < 0.01 ... 0.1 mmol/l ≈ total hardness < 0.05 ... 0.5 °dH |
| vessel material: |
glass-reinforced plastic (grp) steel (coated) stainless steel |
| piping material: |
PVC PP stainless steel |
| ion exchange medium: | ion exchange resin, strongly acidic |
Low. Mainly caused by effluent, and salt consumption during regeneration. Accordingly depending upon the hardness of the raw water, as well as the costs of raw water and common salt.