Role of Surface Pores on Fouling of Polyvinylidene Fluoride Membranes in Submerged Membrane Bioreactors

Abstract

Abstract. In this study, the roles of surface pores on membrane fouling was investigated using three membranes in two lab-scale membrane bioreactors. Characterization of the pristine membranes revealed that increasing polymer concentration decreases pore sizes and porosity. Critical flux was found to decrease with decreasing pore sizes. The finding was consistent for both MBRs. The results of the long-term filtration were in agreement with the flux-stepping test. The fouling layer was easily removed and only a few small particles remained as were observed with scanning electron microscopy. Surface pore sizes and porosity declined for all cleaned membranes, indicating permanent pore blocking, and the effect was higher for membranes with larger pore size. IntroductionMembrane bioreactors (MBRs) improve the conventional activated sludge process (CASP) by replacing the settling tank with a membrane separation. Implementation of MBRs offers advantages, such as reduced plant footprint, lower sludge production, increased process control and improved effluent quality leading to a higher economical value of the effluent. Applications of MBRs gains favorability due to a more stringent effluent standard and the need of effluent reuse. However, the attempts to further decrease operating costs are still being developed, mainly acting on reducing fouling and so increasing process efficiency [1,2].Membrane fouling is the main drawback of MBR operation. It diminishes permeance reflected by an increase in the transmembrane pressure (TMP) when operating under constant flux or a decrease in fluxes when operating under constant TMP. To control fouling, three main approaches are generally followed: exploiting hydrodynamic conditions, improving favourable sludge properties and improving membrane properties. Fouling cannot be completely eliminated, so after a certain period of filtration (weeks, months) extensive cleaning of the membranes is still required and accumulation of permanent fouling will eventually lead to membrane replacement [3,4]. In this study, the effects surface pores of polyvinylidene fluoride (PVDF) membranes on the filtration performance and membrane fouling are investigated. The filterability was evaluated using critical flux methods and long-term filtration.

Cannabinoids and Terpenes as an Antibacterial and Antibiofouling Promotor for PES Water Filtration Membranes

“…Our purpose was to obtain smaller pore sizes in the membranes as irreversible pore fouling is least favorable in membranes with smaller pores, making them convenient for long-term water treatment operation. Conversely, membranes with a higher pore size are prone to blockage by organic materials and would require multiple chemical cleanings for long-term operations [23]. In addition, a smaller pore size of the membrane makes it selectively permeable, hence preventing smaller particles such as bacteria to move across the membrane.…”