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3.4 MEMBRANE AUTOPSY 51
FIGURE 3.9 Example of vessel probing results.
3.4 MEMBRANE AUTOPSY
Membrane autopsy is one of the most common methods for identifying the nature and origin of RO-membrane fouling. This method incorporates sequential completion of series of standard tests in laboratory conditions on membrane elements harvested from RO trains with compromised performance (Chesters et al., 2011). The membrane autopsy procedure includes the following activities:
1. External visual inspection of the membranes, 2. Membrane weight measurement,
3. Bubble & vacuum tests of selected membranes, 4. Standard membrane performance test,
5. Membrane cleaning test,
6. Dye test,
7. Internal inspection and testing, 8. Cell test,
9. SEM,
10. EDaX,
11. Fourier Transform Infrared (FTIR) Spectroscopy, 12. Weight loss on ignition test, and
13. Fujiwara test.
The first five tests listed above are completed with all elements in the actual condition at which they were harvested and are referred to as nondestructive tests. After completion of tests 1 through 5, the membrane elements are dissected and samples of the membrane enve- lopes are collected to perform tests 6 through 13. Because the performance of these tests requires the membrane to be destroyed, they are also referred to as destructive tests. The process of cutting of the test elements to extract samples for the destructive tests is referred to as “membrane autopsy” (Fig. 3.10) and has widely be used in practice as a term for the entire membrane test.
A brief description of each of the 13 membrane autopsy activities along with their purpose and potential outcome are described herein. Usually, the tests are completed as a minimum