A new mass transfer model for oil-containing waste water treatment by low-pressure hollow-fiber ultrafiltration (HFUF) membrane was developed

which considered the axial variation of pressure and local permeation rate since they appeared obviously along the axial distance under low-pressure conditions in practical HFUF process. The numerical simulation was performed by using the orthogonal collocation method (OCM) which was combined with MATLAB software. The predicted results and linear relationship of total permeation rate with inlet pressure

simulated by this model

were in perfect agreement with the experimental data from this study

which proved the rationality of the model and the reliability of the computing method. The simulation showed that radial Peclet number

representing the influence of membrane configuration

solution properties and fluid movement on HFUF process

affected distinctly the radial and axial profile of local or mixing-up concentration. The radial velocity inside the hollow-fiber had a maximum value because of an opposite interaction between the pressure driving force from hollow-fiber center to membrane wall and the diffusion behavior due to the reversed concentration gradient. The average permeation rate decreased with the increase of the axial distance

therefore the final hollow-fiber length would depend on UF efficiency and membrane module cost. Also

the combination algorithm of OCM and MATLAB software displayed its evident advantages of less computer memory space and CPU time. It might be said that the model and the whole simulation software could be employed to provide a suitable selection of HFUF membrane type and technological conditions in both engineering design and actual operation.