AWWA ACE68820

This powerpoint presentation begins by providing a brief overview of the project objective of examining the effect of algogenic organic matter (AOM) on reverse osmosis (RO) membranes during desalination. RO experiments were performed on a semi-automated bench-scale system. A test of algal-laden "red tide" seawater resulted in significant flux decline. It was determined that unicellular marine dinoflagellate algae are the cause of red tide events. Fluorescence microscopy can be used to evaluate and count algal cells. A set of AOM fractionation experiments was performed. Experimental results have the following implications for full-scale operation, including: fairly high levels of organic matter cause only minor short-term flux decline; AOM does accumulate in thick layers; membrane resistance is much higher than cake-layer resistance; bench-scale tests should include autopsy; frequent cleanings are suggested even when performance is steady; shearing of algal cells releases dissolved AOM; and, inlet structures and pretreatment technologies should be designed for low shear if possible. Techniques developed during this research could be valuable for future work, including the following: fluorescence measurements of foulants could help distinguish between algogenic and bacterial fouling; the dichotomy of algae and bacteria can be explored; and, pretreatment strategies can be developed to remove algal cells and minimize AOM release. Includes figures.