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Membrane fouling is one of the main factors that hinders the wide application of ultrafiltration (UF) processes. Limited research on the influence of temperature condition on reversible and irreversible natural organic matter (NOM) fouling has been conducted. Fouling and cleaning of a submerged polymeric UF with different NOM components were examined at 5°C, 20°C, and 35°C. Fouling was evaluated using the modified fouling index-UF (MFI-UF) and unified membrane fouling index (UMFI) indices, analysis of cake layer properties, and specific flux recovery. Results showed that fouling increased by 15%–35% when water temperature decreased from 20°C to 5°C, whereas fouling decreased by 15%–25% when the temperature increased to 35°C. The UMFIf fouling order was consistent across all temperature conditions with the NOM mixture and bovine serum albumin (BSA) fouling more severely than the alginate and humic acid. The UMFI and MFI-UF exhibited the same fouling order and can be used in complement to each other. BSA was found to be more sensitive to temperature changes and irreversibly fouling more than humic acid and alginate. The ratio of irreversible to reversible fouling (UMFIhir/UMFIhr) increased by 15%–25% from 35°C to 20°C and by 30%– 40% from 20°C to 5°C indicating the need for altered cleaning strategies at cold water conditions. [ABSTRACT FROM AUTHOR]

Highlights • Ceramic and polymeric UF fouling experiments were performed using five NOM models. • NOM fouling order was a NOM mixture ≈ BSA > sodium alginate ±Ca+2 > humic acids. • Backwash efficiency was 2× higher for the ceramic UF compared to the polymeric UF. • Hydraulic irreversibility was the dominant fouling resistance during NOM filtration. • Chemical cleaning was found to be effective for both membrane types. Abstract This research examines the effect of various NOM fractions on ceramic and polymeric UF membranes performance in terms of fouling and cleaning. Fouling experiments were performed using five model solutions, humic acid, protein as bovine serum albumin (BSA), alginate with and without calcium, and a combined NOM mixture. Two chemical agents were selected: an oxidant (NaOCl) and caustic (NaOH). Fouling and cleaning behavior were assessed using the resistance in series (RIS) model, membrane permeability, carbon mass balance, and fluorescence excitation and emission matrix (FEEM) analysis. The results demonstrated that NOM fouling order of the ceramic UF was similar to polymeric UF with the following trend: NOM mixture ≈BSA > alginate ±Ca+2 > humic acid. However, the backwash efficiency was 1.5×–2× higher for the ceramic UF in comparison to the polymeric UF, indicating a much higher hydraulic reversibility for the ceramic UF. A carbon mass balance in compliment with FEEM plots determined that NOM removal by the ceramic UF was ≈ 10% higher than the polymeric UF. Chemical cleaning was found to be effective for both membrane types. Thus, it was not possible to conclude, that the ceramic membrane demonstrated an advantage for chemical cleaning under the conditions studied. [ABSTRACT FROM AUTHOR]

Fouling research with polymeric membranes has demonstrated that various natural organic matter (NOM) fractions contribute differentially to membrane fouling behavior. However, limited studies exist analyzing the sensitivity of the MFI-UF to be used as a tool to differentiate NOM fouling components. The results here indicate that MFI-UF is a suitable tool for assessing NOM fouling. Specifically, NOM fouling potential was in the order of organic proteins (as BSA), polymers (alginate), and humic acid, respectively. Further, a mixed solution containing BSA, alginate and humic acid fouled similarly to the BSA solution indicating the high fouling potential of organic proteins in membrane systems. The MFI-UF value was found to increase by > 30% with increasing pressure (1–3 bar) and decreasing temperature (35°C–5°C). The filtered water volume was found to correlate with the MFI-UF values indicating the dependency of the method on testing conditions. Incorporating water viscosity and pressure values against normalized conditions (20°C and 2 bar) with the standard MFI-UF equation was found to be useful to estimate MFI-UF values at variable operating conditions, thus, enhances the potential application range of MFI-UF as a fouling index for NOM. [ABSTRACT FROM AUTHOR]