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Monitoring of softening process

In the animation, the mode of operation of a double softening system on which an OFS residual hardness monitoring device is connected is shown schematically.
At the bottom right, the curve of the corresponding sensor voltage is displayed in parallel.

At the starting point of the animation, the resin of the softening column I is regenerated and ready for use. Softening column II is in readiness. Raw water flows into column I. In the process, the sodium ions shown as red dots are replaced by the calcium and magnesium ions shown as blue dots. The softened and enriched with sodium ions (= red dots) water flows from the softener to the consumer. The water meter installed on the soft water line activates the OFS device for cyclic measurement. The soft water valve opens and soft water samples flow cyclically through the bypass line into the device. The samples are evaluated and then drained off without pressure.

With decreasing exchange capacity of the resin, the residual water hardness rises slightly analogously to the sensor voltage, since less calcium and magnesium ions are exchanged in the soft water. With continuous flow and increasing resin exhaustion, the soft water hardness in flowing soft water increases strongly exponentially. If the flow at the water softening plant is stopped, there is a "counter-ion effect", which results in a reduced residual hardness compared to the last flow measurement. The sensor voltage decreases accordingly. But as soon as soft water is removed again, the sensor voltage rises again analogously to the concentrations of the calcium and magnesium ions in the soft water.

If the threshold value is exceeded, a counter-measurement in the raw water is carried out to calibrate the sensor. If the subsequent measurement in soft water continues to exceed the specified threshold, external regeneration is started and softener I is switched to softener II. The following tension measurements in soft water from softening column II are, in trouble-free condition, below the threshold value and the softening process continues to be monitored analogously to the procedure described for softening column I.