Microfiltration with silicon nitride microsieves and high frequency backpulsing

Abstract

Silicon nitride microsieves are microfiltration membranes manufactured with techniques commonly used in the semi-conductor industry for wafer production. These membranes are characterised by the uniform pore size and the high porosity. Furthermore, due to their extremely thin selective layer and the relative open support structure, the clean water fluxes are usually very much higher (an order of magnitude of at least 100 times higher) than the conventional microfiltration. This extremely high fluxes causes the microsieves to be extremely susceptible to fouling and flux decline during filtration. As such, a new operating technique, i.e. high frequency backpulsing is introduced to keep the microsieve surface cleaned and to maintain the high fluxes. This paper discussed the mechanism used to create backpulses at very high frequency and the impact of such high frequency backpulses on particulate and nonparticulate fouling of the microsieves were studied with different model solutions.