Assessing the linkage between feed water quality and reverse osmosis membrane performance

The scarcity of fresh water in most of the countries in the Mediterranean Basin makes desalinated seawater a valuable alternative water source. It is therefore imperative to develop and adapt reverse osmosis (RO) methods to minimize water production expenses. Management modeling allows identifying preferable directions of implementation. Usually, desalination depends on a combination of a series of controlling parameters. These include feed water quality; required resulting qualities; and operational conditions determined by the membrane characteristics, flux and operating pressure head. Frequently it is difficult to select the best membrane for the RO process due to the complexity of the processes and the abundance of information that is provided by the membrane manufacturers. Taking available data (from RO membrane manufacturer catalogues) enables defining clusters of parameters with similar properties for improved control of the desalination process. According to the analysis, it was shown that there is a similar parameterization between the Silt Density Index (SDI) and the membrane flow rate. Other clusters were found as well. This analysis can be further developed into larger clusters leading to distinguishing two major facets: (1) the permeate and (2) RO membrane rejection; each includes several parameters. This showed that corresponding managing tools can simplify the membrane selection process and ultimately diminish production expenses.

A management model was developed, defining clusters of similar membrane operational regions. The model provides a first approximation of membrane behavior by means of facet analysis. Membrane performance is discussed in terms of measured variables, permeate flow and salt passage. The analysis provides the rational for an hypothesis concerning the interrelationships among components of water quality and membrane operational characteristics. The model predicts that permeate flow is mainly characterized by SDI while salt passage is influenced by high temperatures.