Abstract
To understand impacts of organic adhesion on membrane fouling, ultrafiltration (UF) membrane fouling by dissolved natural organic matter (NOM) was investigated in the presence of background cations (Na+ and Ca2+) at typical concentrations in surface water. Moreover, NOM adhesion on the UF membrane was investigated using atomic force microscopy (AFM) with colloidal probes and a quartz crystal microbalance with dissipation monitoring (QCM-D). The results indicated that the adhesion forces at the NOM-membrane interface increased in the presence of background cations, particularly Ca2+, and that the amount of adhered NOM increased due to reduced electrostatic repulsion. However, the membrane permeability was almost not affected by background cations in the pore blocking-dominated phase but was aggravated to some extent in the cake filtration-governed phase. More importantly, the irreversible NOM fouling was not correlated with the amount of adhered NOM. The assumption for membrane autopsies is doubtful that retained or adsorbed organic materials are necessarily a primary cause of membrane fouling, particularly the irreversible fouling.
Highlights
Because of outstanding advantages such as low-pressure running, small footprint, and high compatibility with other water purification technologies, ultrafiltration (UF) is increasingly applied in potable water treatment to meet stringent requirements for water quality
It can be observed that the hydrophobic, transphilic, and hydrophilic fractions account for 46%, 18%, and 36%, respectively, of the total organics in the dissolved natural organic matter (NOM) in terms of dissolved organic carbon (DOC)
The adhesion forces were normalized by the radius of the colloidal probe used
Summary
Because of outstanding advantages such as low-pressure running, small footprint, and high compatibility with other water purification technologies, ultrafiltration (UF) is increasingly applied in potable water treatment to meet stringent requirements for water quality. The DOC rejection was higher than that expected desorption processes, respectively, implying that the residual layer was much looser than the adhesion based on the molecular weight distribution of NOM (Figure 1b), because size exclusion as well as layer. In the presence of Na+ and Ca2+ , the absolute values of ∆D/ ∆F decreased to 0.508 and 0.474, membrane absorption and cake layer retention were involved in the removal of organics during respectively, in the adhesion process. This result indicates that the adhesion layer on the membrane filtration [24]. In the absence of cations, the membrane was severely fouled, with the flux decreasingafter by filtering mL NOM solution, and the flux decline slowed,slowed, with a specific flux of flux after100 filtering
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