Membrane Filtration Characteristics in Membrane-Coupled Activated Sludge System: The Effect of Floc Structure on Membrane Fouling

Abstract

The membrane-coupled activated sludge (MCAS) process has many advantages over the conventional activated sludge system, but the inherent membrane fouling problem still remains to be solved. However, it is not yet advanced enough to understand the reliable fouling mechanism. The strength of the MCAS process lies in the almost complete removal of suspended solids from the activated sludge broth. But it has made us overlook the effect of sludge morphology and physiology on membrane flux which is one of the key factors in deciding the economical feasibility of the MCAS system. The aim of this study was to investigate membrane filtration characteristics in the MCAS process, especially to correlate floc structures of the activated sludge with membrane fouling. A series of ultrafiltrations with both hydrophilic and hydrophobic membranes using the stirred batch cell system was performed to assess flux behavior according to the floc structures of the activated sludges (normal, pinpoint, and bulking activated sludge). The order of fouling tendency was found to be normal sludge Ͻ pinpoint sludge Ͻ bulking sludge. Also, all the membranes behaved in the same way. The cake layer resistance (R c ) made up most of the total resistance (R t ), but the fouling resistance (R f ) was negligible in any floc structure. The key factors controlling the R c were the shape and size of the activated sludge flocs and the porosity of the cake layer accumulated on the membrane surface. ORDER REPRINTSmembrane showed a greater fouling tendency than the hydrophilic membrane regardless of the microbial floc structures. The difference in fouling tendency between the two membranes was attributed to the hydrophobic interactions between the membrane and floc surfaces.

The effect of polymer concentration on flux stability of polysulfone membrane

“…It has been known that fouling on a membrane surface alters the separation characteristic of the membrane [38,39]. Low cross flow velocity and transmembrane pressure lead to higher concentration of the rejected solute on the membrane surface, due to the longer time of membrane exposure to the raw water.…”

Biomass Characteristics, Aeration and Oxygen Transfer in Membrane Bioreactors: Their Interrelations Explained by a Review of Aerobic Biological Processes

“…Many correlations linking oxygen transfer and aerobic biological system characteristics are found in the literature, simple or complex, depending on the parameters considered (Fujie et al 1992;Van Weert et al 1995;Boumansour & Vasel 1998;Abbassi et al 1999;Chang et al 1999;Chang & Fane 2000;Garcı´a-Ochoa et al 2000;Hebrard et al 2000;Badino et al 2001Badino et al , 2001Chern et al 2001;Lu et al 2001;Ozbek & Gayik 2001;Ozaki & Yamamoto 2001;Chisti & Jauregui-Haza 2002;Garrido Hoyos et al 2002). However, these correlations are difficult to apply to other systems than the one they are characterising.…”

État actuel des connaissances des procédés de bioréacteur à membrane pour le traitement et la réutilisation des eaux usées industrielles et urbaines

“…Le choix des produits chimiques se fait en fonction de la nature du matériau membranaire, afin de respecter les limites de pH et de température ainsi que la tolérance au chlore, aux autres désinfectants et acides. Dans les conditions normales, les solutions généralement utilisées pour le nettoyage chimique sont l'hypochlorite de sodium (NaOCl) pour détacher les matières organiques et l'acide citrique (C 6 H 8 O 7 ) pour les inorganiques (CHANG et KIM, 2005;CHANG et al, 1999;LE-CLECH et al, 2006;LEE et al, 2003). Il est fréquent que les fabricants de membranes proposent des protocoles spécifiques pour le nettoyage chimique.…”