Investigation of Seawater Desalination Reverse Osmosis Membrane Biofouling

One of the challenges the seawater desalination industry faces today is reverse osmosis (RO) membrane biofouling. Currently, Seawater pretreatment methods such as oxidant-based disinfection, ultraviolet irradiation, and coagulation followed by granular media or membrane filtration could reduce the number of bacteria in feed seawater, but would typically not eliminate biofilm formation on the RO membranes. Traditional water quality parameters recommended by the membrane manufacturers are often inadequate at protecting the membrane from biofouling. This research investigated alternative seawater desalination RO membrane biofouling indicators in a Southern California desalination plant. Environmental and water quality parameters were collected onsite over two years and were analyzed statistically. The results of this study indicated that biofouling was significantly correlated with changes of water quality parameters including TOC, UV254, chlorophyll fluorescence in raw seawater, and suggest that they can be used to predict the membrane biofouling events. In an effort to mitigate SWRO membrane biofouling, different concepts of alternative pretreatment strategies are explored and evaluated. The concept of balancing the carbon, nitrogen and phosphate concentration in RO feed water was explored and showed to reduce biofilm formation during the period of high fouling potential. In-situ assessment of biofouling potential of subsurface intake seawater also demonstrated the feasibility of the intake design to reduce membrane biofouling.