Performance degradation in hollow fiber hemodialysis modules due to blood-induced fouling: experiments and simulations

A novel experimental method was developed to assess the impact of blood-induced fouling on the membrane hydraulic permeability L-p in hollow fiber hemodialysis modules. Fouling was induced by conducting 2-h and 4-h in vitro hemodiafiltration treatments using bovine blood. L-p was then determined in both clean and fouled modules by applying a hydraulic characterization technique recently proposed in the literature, which requires measurements of pressure at four module locations under two flow modalities. L-p was found to decrease by 42% and 57% after two and four hours, respectively, in qualitative agreement with literature results. The impact of the changes in L-p on the convective component of solute removal performance was then assessed using a purpose developed simulation model. The results showed that, for middle molecular weight solutes such as beta 2-microglobulin, the degradation of L-p due to fouling is responsible for a decrease of the delivered dialysis dose ranging from ~17% to ~23% according mainly to the blood flow rate, with a lesser influence of other quantities (module length, bundle porosity and dialysate flow rate). The performance degradation was much less significant (3-4%) for small solutes like urea.