Prevention of Membrane Fouling by High-Efficient Microfiltration Accompanied With Cyclic Backwashing

Abstract

This paper presents an experimental investigation of constant rate and constant pressure microfiltration behaviors of sewage secondary effluent, pretreated with polyaluminum chloride (PAC). The microfiltration unit was tubular module with monolithic ceramic membrane. The experimental apparatus designed specially for this work is fully automated, has backwashing capability and was operated in deadend mode. Membrane fouling encountered in the microfiltration of sewage secondary effluent represents serious design and operational concem. The apparatus was designed in such a way that when the pressure drop or flux reaches a pre-set value, backwashing is initiated. Based on the intermediate blocking law, the mathematical model has been developed to explain the pore blocking behavior. This work clearly indicated that constant pressure filtration characteristics of sewage secondary effluent can be derived from the results of constant rate experiment. The energy consumption and net filtrate flux were calculated and compared with the experimentally measured data. The most interesting result of this work is that there exists an optimum pressure increment for each net filtrate volume. However, further assessment of energy consumption and product indicated that when the optimum operational conditions are determined, there should be a trade off between the energy consumption and the effective flux. Furthermore, this work also proved that constant pressure filtration with cyclic backwashing operation is desirable in industrial application. Water quality analysis showed that the filtrate is free from microorganisms and can be used as reclaimed water for toilet flushing, car washing, etc.