Investigation On Deep Bed Filtration With Fibrous Bundle Media

It has been a topic of great significance so far to research the effluent quality and efficiency of depth filtration and extension of its application, due to intensification of water pollution and shortage of water resources.As a new type of filtering device, fibrous bundle media filter, with the features of high rate filtration , high quality effluent .small resistance to flow and great retaining capacity , is employed in many techniques. However, theoretical investigation have not been as successful, mainly due to the inherent complexities and the transience of filtration processes. It is, therefore, fundamental work to investigate the theories necessary for the designing and operating of filter.An experiment for comparison of suspended particles of different diameter, different superficial filtration velocity and different operation parameters was conducted. The results of experiment show the influence of diameter of suspended particles, superficial filtration velocity and operation parameters on characteristics of filtration processes. On the basis of experimental study an analysis of deposit morphology, head loss equation and dynamics model of fibrous bundle media depth filtration was established.An experimental study was conducted about the influence of diameter of suspended particles and different superficial filtration velocity on removal efficiency of particles and head loss of fibrous bundle media direct filtration. The relevant data of the experiment will contribute to the establishment of head loss equation and dynamics model.The morphology of deposits formed during filtration was photographed with scanning electron microscope and was determined by using the fractal theory. The results show that not only the pore structure of deposits is a fractal object,but also the distribution of pore sizes possesses fractal characteristics, and the surface of deposits has a self-similar structure.An equation of head loss of fibrous bundle media filter is derived on the basis of cylinder cell model, and for the first time , a new concept of direction factor is advanced and used to revise the relationship between flow direction and axes of fiber. Moreover, comparison between dimensionless permeability predicted by various equations and experimental data indicates that the new equation established agrees reasonably well with the experimental data.On the basis of experimental study, and by using unit bed element and cylinder cell model, clean bed filter coefficient was derived by correlating dimensionless groups for London, relative size and gravity. It has shown that the suspended particle removal mechanism can be described by parameters representing the interception and London--Ven der walls force, semi-empiric expression of filter coefficient was established under the assumption that filter coefficient is the function of the specific area and the interstitial velocity. Furthermore, on the basis of phenomenological model and cylinder cell porous media model, a dynamics model was developed. Moreover, comparison between the semi- empiric expression predictions and experimental data show that both agree with each other.The series method has been developed to solve the dynamics model. Results from these solutions are compared with the experimental data , and the predicted results are in good agreement with the experimental data. It is also indicated that the dynamics model is reasonable.