Symptoms of calcium carbonate scale include:
- Scale extruding out of the downstream end of the last membranes in the system.
- All of the scale dissolves when introduced to a dilute hydrochloric acid solution.
- Poor salt rejection, low flow, and or, high pressure differential on individual membrane test data.
- 8” x 40” Element weight exceeds 45 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 approaches are:
- Low pH clean with RoClean L403.
- In severe cases, add hydrochloric acid to the cleaning solution to maintain a pH of 3.0.
Testing for calcium carbonate scale:
Calcium carbonate scale is not always as white as shown in Figures 1 and 2. But, a quick test can be conducted to see if the foulant is comprised solely of calcium carbonate.
In a glass beaker, make a 1:1 dilution of HCl and DI water. Drop a small sample of the foulant into the solution. If the foulant contains calcium carbonate, it will bubble (see Figure 3). Continue adding acid until the bubbling stops or until the scale disappears.
If the beaker contains residual material after the bubbling has stopped, then the foulant consists of more than just calcium carbonate.
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