Mutual Influences between Natural Organic Matter and Inorganic Particles and Their Combined Effect on Ultrafiltration Membrane Fouling

Abstract

Fouling is one of the most critical aspects of membrane technology and is strongly influenced by natural water characteristics.This studyfocuses on a mechanistic understanding of the impact of interactions between natural organic matter (NOM) and particles on fouling. The model substances used were humic acid, alginate (polysaccharide), and kaolinite. NOM-kaolinite adsorption experiments, particle characterization, and dead-end ultrafiltration (UF) batch experiments were performed. The adsorption experiments indicated particle stabilization at low NOM equilibrium concentrations, whereas calcium induced significant aggregation, especially with alginate. UF experiments implicated a synergistic fouling effect of particle-NOM combinations, which was greatly reduced by calcium. Moreover, irreversible NOM fouling was only prevented by particles in the presence of calcium. On the basis of our results, we present a mechanistic model suggesting that synergistic fouling effects occur due to particle stabilization by NOM adsorption, especially shown for HA, and antagonistic effects due to particle destabilization by calcium. However, synergistic fouling can also be based on sterical interferences between larger NOM in the form of polysaccharides and particles during simultaneous pore blocking and cake formation. A heterogeneous NOM-particle fouling layer is ultimately formed with membrane associations dominated by NOM. The combined fouling is conclusively determined bythe type of NOM, its specific fouling mechanisms, and its particle interactions prior to and during the filtration process.

Investigation of organic foulants behavior on hollow-fiber UF membranes in a drinking water treatment plant

“…Varbanets et al [10] found that hydrophobic humic acids made an increase in resistance at ultra-low pressure UF membrane system by investigating seven types of water. Jermann et al [11] set up a series of dead-end UF batch experiments to observe the fouling of humic acid, alginate and kaoline. They reported that humic substances caused severe irreversible fouling due to adsorption, while alginate should have a most detrimental effect on membrane fouling, but mostly reversible.…”

Insight into the combined colloidal-humic acid fouling on the hybrid coagulation microfiltration membrane process: The importance of aluminum

“…Previous research suggested that NOMs especially humic substances could improve the stability of particle suspension, and that divalent cations would destabilize them [16,17]. More recently, some specific fractions of NOMs were found to be effectively destabilized in the presence of particles [18].…”

“…Other researches [27] also reported the addition of coagulants aggravated fouling in coagulation-membrane filtration process. Researches on combined fouling of NOM-particle on membrane filtration process have been published in the past few decades [18,28,29]. These contradictory results might be attributed to the fact that the mutual interaction among colloidal-NOM has important effect on membrane fouling.…”

Assessing Synergistic Ultrafiltration Membrane Fouling by TiO2 Nanoparticles and Humic Acid Using Interaction Energy Analysis

“…Therefore, the presence of NOM is expected to influence the membrane fouling mechanism. Earlier studies have observed a synergistic effect between NOM and common inorganic colloids on membrane fouling [14][15][16]. Jermann et al [15] found a significant stronger flux decline during the filtration of mixed solutions consisting of humic acid and kaolinite particles, in comparison with individual foulants.…”

“…Earlier studies have observed a synergistic effect between NOM and common inorganic colloids on membrane fouling [14][15][16]. Jermann et al [15] found a significant stronger flux decline during the filtration of mixed solutions consisting of humic acid and kaolinite particles, in comparison with individual foulants. Compared with common inorganic particles, the high surface-area-to-volume ratio makes the behavior of nanoparticles during membrane filtration significantly different.…”