Thermodynamic analysis of membrane fouling in a submerged membrane bioreactor and its implications

Membrane fouling in a submerged membrane bioreactor: Impacts of floc size

“…Pore clogging fouling highly depends on the match of particle size and membrane pore size [6]. Recent studies suggested that adhesion of flocs to membrane surface in MBRs is a thermodynamic process [23][24][25]. While hydrodynamic forces forward the flocs close to the membrane surface, it is the thermodynamic forces (thermodynamic interactions) that cause binding (adhesion) of the flocs to the membrane.…”

“…The former stems from permeate flux, and the latter consists of Brownian diffusion, inertial lift and shear induced diffusion [22]. From the hydrodynamic viewpoint, hydrodynamic forces just take the roles of bringing the flocs close to the membrane surface, but are not responsible for the actual binding (adhesion) of flocs on the membrane surface [23,24]. Both small and large flocs can be forwarded to the vicinity of membrane surface by hydrodynamic forces.…”

Influence of membrane surface roughness on interfacial interactions with sludge flocs in a submerged membrane bioreactor

“…By using XDLVO analysis, Feng et al [9] found that a dominating strain (Klebsiella oxytoca) in cake layer had stronger attractive interactions with polypropylene (PP) membrane than polyvinylidenefluoride (PVDF) membrane in a MBR. Hong et al [13] reported that, as compared to large floc, small floc would adhere to membrane more easily in a MBR due to its higher attractive specific interaction energy (interaction energy per unit mass). Zhang et al [14] found that, by adding polyvinyl alcohol (PVA) into membrane casting solution, the prepared modified PVDF/polyethersulfone (PES) blend membrane possessed enhanced energy barrier with SMP, which therefore reduced the adsorption of foulants in a MBR.…”

Effects of surface charge on interfacial interactions related to membrane fouling in a submerged membrane bioreactor based on thermodynamic analysis

“…The interfacial interactions consist of three types of interactions: Lifshitz-van der Waals (LW), acid-base (AB), and electrostatic double layer (EL) interaction which surface charge is pertained to. A lot of studies have evidenced the feasibility of XDLVO in predicting and interpreting some membrane fouling phenomena in MBRs [11,12,19]. Therefore, XDLVO theory may provide a useful tool to explore the exact roles of surface charge in membrane fouling, and explain the conflicting conclusions in literature as well.…”

“…Foulant adhesion in MBRs is a complicated process which depends on both of bioreactor hydrodynamic and thermodynamic conditions regarding foulants and membrane [3]. It is generally believed that hydrodynamic conditions take roles of bringing foulants to the vicinity of membrane surface, whereas, thermodynamic conditions indicated by interfacial interactions between foulants and membrane directly determined the eventually binding the foulants to membrane surface [11,12]. Surface charge is one of the primary surface parameters of a substance, and no doubt plays important roles in the interfacial interactions and membrane fouling in MBRs.…”