The International Desalination Association World Congress on Desalination and Water Reuse 2013 / Tianjin, China REF: IDAWC/TIAN13-117 ULTRAFILTRATION AS PRETREATMENT TO REDUCE ALGAL BLOOM IN REVERSE OSMOSIS PLANTS Authors: R. Sandín, B. Corzo, E. Ferrero, J. Bacardit, J. J. Malfeito Presenter: Jorge J. Malfeito R&D Director- Acciona Agua - Spain e-mail: jorgejuan.malfeito.sanchez@acciona.com Abstract Pretreatment of seawater for desalination can be accomplished by microporours membranes such as microfiltration (MF) or ultrafiltration (UF). One problem with microporous membranes pretreatment is fouling by marine algae, which is most prevalent during algal blooms. Algal cells quickly block MF and UF pores and decrease permeability. The cells attached to the membrane secrete and produce extracellular polymeric substances (EPS) which accumulate on the surface and cause the flux decline. In this study, Scenedesmus algae specie was cultured by Acciona Energia in a tubular reactor with a capacity of 700 liters. These algae are approximately 10 μm of size and are ellipsoidal in shape. EPS attached to the cell surface and secreted into its growth medium were analyzed with different analytical tools such as Liquid Chromatography-Organic Carbon Detection and Organic Nitrogen Detection (LC- OCD-OND), Excitation–Emission Matrices fluorescence spectroscopy (EEM), Fourier Transform Infrared-Attenuated Total Reflectance (ATR-FTIR), carbohydrate concentration and protein concentration. In this research, a pilot test was performed to evaluate the operational parameters during algal blooms. An UF membrane was tested in several trials with a constant flux of 54 l/m 2 h as a pretreatment process to Seawater Reverse Osmosis Desalination. The membrane area was 0.92 m 2 and the pore size 100,000 Nominal Molecular Weight Cutoff (NMWC). Filtration process was evaluated with three different concentrations of algae to simulate an algal bloom; 5.72•10 8 cell/L, 3.15•10 9 cell/L and 5.72•10 9 cell/L. By the statistical analysis carried out by Statgraphics it is possible to conclude that algae concentration is more critical parameter than the filtration conditions during algal blooms. At the beginning of the filtration run, only algal concentration must be considered. However, once a filtration run went ahead, other variables (filtration time and backwash (BW) duration) showed influence on the trans-membrane pressure (TMP) although in minor way than algal concentration.