Predictive models and factors affecting natural organic matter (NOM) rejection and flux decline in ultrafiltration (UF) membranes

Prediction equations for NOM rejection were formulated using parameters, including specific UV absorbance [SUVA = UV absorbance at 254 nm/dissolved organic matter (DOC)] and a f/k ratio [a ratio of water permeability (f) to the mass transfer coefficient (k)], which have been found to influence aspects of NOM and operating conditions, respectively. Attempts were made to formulate relationships between adsorption resistance (R-a) and interfacial membrane concentration (C-m), and specifically between the amount of NOM absorbed (mg C/cm(2)) and the R-a. Flux decline was also formulated in two ways: (1) by the (so-called) empirical flux-decline equation with three flux-decline coefficients, and (2) by the adsorption flux-decline model with two NOM adsorption terms between bulk, the NOM and the membrane surface and an existing NOM adsorption layer.