Membrane fouling in seawater desalination processes caused by harmful dinoflagellate Cochlodinium polykrikoides

Abstract

Eutrophication of the world’s marine environment has been exacerbated due to discharge of a large volume of wastewater from rapidly growing cities. Between 2008 and 2009, a serious red tide appeared in the Gulf that brought about a temporary shutdown of water desalination plants in Oman and the UAE. In this study, a harmful dinoflagellate Cochlodinium polykrikoides known to be the cause of many red tides, including the one in the Gulf between 2008 and 2009, was cultured in the laboratory to investigate its impacts on a coagulation-microfiltration/ultrafiltration (MF/UF)-reverse osmosis (RO) desalination process. The culture medium for C. polykrikoides contained high amounts of dissolved organic matter that possessed fluorophores for fulvic-like, humic-like, and protein-like organic matter that can be detected by excitation-emission matrix (EEM). Although EEM peaks were diminished by coagulation-MF/UF, the reduction in dissolved organic carbon concentrations was not significant by MF and was small by UF. Both MF and UF filtrates showed strong RO filtration resistance, so that they have to be diluted 10 times to be able to be filtered by RO membranes. RO membrane fouling was more serious with MF filtrate than with UF filtrate possibly because of the difference in quantity and quality of organic contents in MF and UF filtrates. However, the RO membrane could reject most of the organic matter in both MF and UF filtrates.