Symptoms of sulfate scale include:
- Material extruding from the downstream end of the last membranes in the system.
- Foulant will not dissolve when introduced to a dilute hydrochloric acid solution.
- Poor salt rejection, low flow, and/or high pressure differential on individual test data.
- 8” x 40” element weight exceeds 40 pounds.
- Site reports interruption in the antiscalant or acid injection.
- Site reports scale in the last vessel or piping of the concentrate stream.
The recommended cleaning approach varies:
- If some of the material dissolved in a dilute hydrochloric solution, begin the clean with a low pH product such as RoClean L403.
- If none of the material dissolved in a dilute hydrochloric solution, then skip the low pH clean and use only a high pH solution, RoClean L811.
- If possible, heat the cleaning solution to the maximum temperature allowed by the membrane manufacturer.
Additional Notes:
Barium sulfate scale on a membrane, pressure vessel, or pipe feels like fine grit sandpaper. This abrasiveness can cause damage to a membrane surface during system operation. When the system is started and stopped, the vexar (feedspacer) material shifts slightly. This shifting can cause the barium sulfate scale to scratch the membrane surface causing permanent damage and resulting in a loss of rejection.
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