Baffled microfiltration membrane and its fouling control for feed water of desalination

Pretreatment process is a significant factor in the success of desalination process. It plays a key role in enhancing the lifetime of RO membranes in desalination process. Microfiltration process is emerging as an alternative solution for desalination pretreatment process. The baffled microfiltration membrane has its attractive features in fouling control and flux improvement for the feed water for desalination. Turbulence promoters such as helical baffles have distinct possibilities to enhance permeate flux during crossflow microfiltration. Helical inserts reduce hold-up in the feed channel; increase fluid velocity and wall shear rates and produce secondary flows or instabilities. The overall objective of this work was to investigate the influence of helical baffles on permeate flux during the microfiltration process. TiO2 dispersion was used to represent the microfiltration particle. Tubular, single channel ceramic membranes with nominal pore size of 0.2 µm were used. Variations of the helical baffle geometries, which are the number of turns per baffle length, were investigated. It was found that the insertion of helical baffles had increased the permeate flux. In some cases, the increase was more than 100%. The effect of a number of turns per baffle length showed that the permeate flux increased with the number of turns but decreased when the number of turns was more than 4 turns per 50 mm baffle length. Thus, the optimum number of turns was 4 turns per 50 mm.

The results of the current research show that microfiltration can be used as pretreatment for feedwater prior to reverse osmosis membranes to reduce the fouling phenomena in desalination process. The use of helical baffle inserted in the MF can further enhance and control the fouling in the MF itself. The effect of different helical baffle geometries and shape has been explored and the optimum baffle was identified. Baffled microfiltration can enhance the average flux up to 104.9% compared to a run without baffle using optimum baffle geometries of 4 turns/50 mm baffle length. The feasibility of the current study was investigated using TiO2 particle which very seldom exists in the feedwater of desalination process. However, TiO2 can represent any type of inorganic micro particles, suspensions or dispersions which may exist in feedwater of a desalination plant.