A more effective method for fouling characterization in a full-scale reverse osmosis process

Membrane fouling is customarily indicated and measured by permeate decline at constant operating conditions. Although this method has been widely used for many years, it is inadequate for characterizing fouling development in modern full-scale RO processes. It has been demonstrated that in some full-scale RO processes with highly permeable membranes, the initial development of membrane fouling may not apparently affect the permeate flux. When the permeate flux is noticeably affected, the membrane is so severely fouled that restoration to its original permeability may become impossible. In this study, the permeate flux of a full-scale RO process and its controlling mechanisms are studied with numerical simulations. Particular attention is given to the relationship between permeate flux and the change of membrane resistance. Results show that the filtration coefficient (a collective parameter related to distribution of the membrane resistance) can be a better indicator or measurement of membrane fouling in a full-scale RO process. With this new fouling indicator, the development of membrane fouling in a full-scale RO process under any conditions can be accurately characterized. The advantages of the new characterization method include early and accurate indication of fouling development and quantitative assessment on the effectiveness of membrane cleaning.