Page 74 - ro membanes

3.4 MEMBRANE AUTOPSY 57
cleaning solutions and their sequence of implementation to achieve maximum recovery of RO-membrane productivity and salt rejection and to minimize the membrane differential pressure. As a result of this test, the laboratory completing the membrane performance anal- ysis prepares recommendations for efficient and cost-effective membrane cleaning.
3.4.6 Internal Inspection and Testing
Internal inspection and testing is completed as a part of the membrane autopsy. The anti- telescoping devices are first removed and the surface of the membranes is inspected for accu- mulation of solids, colloidal particles, biofouling, feed/brine spacer extrusion, and telescoping. Fig. 3.15 depicts the inner surface of the front ATD and the feed scroll. As seen from this figure this membrane is exposed to severe particulate fouling.
Once the membranes are opened along their length and unrolled into individual mem- brane leafs, the internal surface of the membrane leafs is visibly inspected for surface contam- ination, accumulation of debris, biofilm accumulation, and collection of scale on the RO membrane surface.
Fig. 3.16 presents membrane opened for internal membrane inspection. In this particular case, the membrane surface is covered with brown-colored biofilm, indicating heavy micro- bial membrane biofouling.
Besides the end caps and membrane surface, the membrane leafs are also inspected for the condition of their glue line integrity. As indicated in Chapter 1, membrane leafs are glued on the three sides and open to the permeate tube, forming an envelope. Glue lines of the mem- brane envelopes are inspected for failure (glue flaps, pouching, and delamination). Glue flaps are sections of unbounded (unglued) material, which could obstruct, and therefore hinder the spacer flow.
FIGURE 3.15 Accumulation of particulate debris on the front of the element and end cap.