Page 69 - ro membanes

52 3. DIAGNOSTICS OF MEMBRANE FOULING AND SCALING
FIGURE 3.10 Membrane dissection.
on one front-membrane element, located in the first position near the entrance of the feed water to the RO vessel, and on one tail-RO element located at the last position in the RO vessel. The front RO-membrane element experiences the highest magnitude of particulate, organic, colloidal and microbial fouling while the last RO element is potentially exposed to the worst-case scaling conditions that may occur in the vessels.
Preferably, it is recommended to perform membrane autopsy on a complete set of all elements in at least one vessel within the RO train. The selected membrane set should be representative for the performance challenges of the entire RO train and of the desalination plant RO system, if possible. If the RO system is experiencing a number of different chal- lenges, it is desirable to harvest several complete sets of RO elements operating at conditions reflective of respective RO system challenges.
Membrane autopsy is typically performed by commercial or university laboratories specialized in such services, which have all the necessary instrumentation, test equipment, and skilled staff to complete the tests. It is preferable that the RO membranes sent for autopsy are accompanied with the original factory documentation for these elements, if available.
3.4.1 External Visual Inspection
Once they arrive at the test laboratory, RO membrane elements are first inspected by visual observation to identify potential physical damages of the fiberglass casting, the core tube, brine seals, and antitelescoping devices (ATDs), as well for telescoping, extrusion of the brine spacer, and discoloration of the ATDs. In addition, the surface of the front end ATD is inspected for accumulation of solids, unusual odors, and biofilm. The surface of the tail end caps is typically inspected for accumulation of crystals of mineral scale.