Membrane Fouling Potential of Secondary Effluent Organic Matter (EfOM) from Conventional Activated Sludge Process

Abstract

Secondary effluent organic matter (EfOM) from a conventional activated sludge process was filtered through constant-pressure dead-end filtration tests with a sequential ultrafiltration (UF, molecular weight cut-off (MWCO) of 10k Dalton) and nanofiltration (NF, MWCO of 200 Dalton) array to investigate its membrane fouling potential. Advanced analytical methods including liquid chromatography with online carbon detection (LC-OCD) and fluorescent excitation-emission matrix (F-EEM) were employed for EfOM characterization. EfOM consisted of humic substances and building blocks, low molecular weight (LMW) neutrals, biopolymers (mainly proteins) and hydrophobic organics according to the sequence of their organic carbon fractions. The UF rejected only biopolymers and the NF rejected most humics and building blocks and a significant part of LMW neutrals. Simultaneous occurrence of cake layer and standard blocking during the filtration process of both UF and NF was identified according to constant-pressure filtration equations, which was possibly caused by the heterogeneous nature of EfOM with a wide MW distribution (several ten to several million Dalton). Thus the corresponding two fouling indices (kc for cake layer and ks for standard blocking) from UF and NF could characterize the fouling potential of macromolecular biopolymers and low to intermediate MW organics (including humics, building blocks, LMW neutrals), respectively. Compared with macromolecular biopolymers, low to intermediate MW organics exhibited a much higher fouling potential due to their lower molecular weight and higher concentration.

Practical use of standard pore blocking index as an indicator of biofouling potential in seawater desalination

“…HS is hydrophobic-DOC fraction of seawater. These compounds are mainly removed due to the potential electrostatic interaction [34]. Thus, it could not be removed by hydrophilic UF membrane.…”

Fouling Mechanisms Analysis via Combined Fouling Models for Surface Water Ultrafiltration Process

“…Therefore, the four fouling mechanisms in the UF process of the surface water could occur simultaneously in theory. Wei and Amy [ 26 ] found the simultaneous occurrence of two fouling mechanisms during the UF process of the wastewater treatment plant effluent. Corbaton et al [ 27 ] found that single models did not characterize the membrane fouling mechanism.…”

Fractionation of secondary effluents of wastewater treatment plants in view of the evaluation of membrane fouling in a further ultrafiltration step

“…Each of these components or fractions will contribute differently to membrane fouling due to individual properties, for example, hydrophobicity and charge . The success of the fractionated methodology decreases with the number of separated fractions.…”

“…Each of these components or fractions will contribute differently to membrane fouling due to individual properties, for example, hydrophobicity and charge. 19 The success of the fractionated methodology decreases with the number of separated fractions. In addition, a major problem with these techniques occurs when organic matter compounds irreversibly adsorb onto the resin and consequently these fractions cannot be recovered.…”