Appendix 5. Autopsy and cleaning of reverse osmosis elements affected by harmful algal bloom-contaminated seawater.

Abstract

Following an algal bloom, if a change is observed in the reverse osmosis (RO) performance, an initial visual plant inspection should be carried out, including looking at and removing cartridge filters and membrane elements from different positions in the pressure vessel. Fouling may be a combination of organic, biofouling, particulate, and metal hydroxide. Biofouling is often slimy or gelatinous which may be accompanied by a bad smell while iron fouling is a reddish brown deposit. Figure 1 shows evidence of biological fouling on a cartridge filter and inside a pressure vessel following an algal bloom event. If it is obvious that there is severe fouling, membrane autopsy would be the most appropriate tool for identifying the nature of the foulant, and the best cleaning protocol for removal of the foulant. Autopsy results would be interpreted in conjunction with an analysis of plant performance data.