Effect of sludge properties on the filtration characteristics of self-forming dynamic membranes (SFDMs) in aerobic bioreactors: Formation time, filtration resistance, and fouling propensity

Abstract

This study attempts to elucidate the effect of sludge properties on the formation time, filtration resistance, and fouling propensity of self-forming dynamic membranes (SFDMs), developed on coarse-pore filters in aerobic wastewater treatment bioreactors. Short-term filtration experiments were performed with twenty aerobic sludge samples having twelve sludge properties characterized. Statistical analysis showed that mean particle diameter (Dvm) associated with particle size distribution strongly affected both formation time (rp=−0.803, p=0.000) and filtration resistance (rp=−0.733, p=0.000) of SFDMs, whereas relative hydrophobicity (RH) exhibited a moderate correlation with SFDM formation time (rp=−0.487, p=0.029). In contrast, four other different sludge properties, i.e. viscosity (rp=0.811, p=0.000), extractable extracellular polymeric substances (eEPS) (rp=0.723, p=0.000), the carbohydrate content of eEPS (rp=0.766, p=0.000), and specific oxygen uptake rate (SOUR) (rp=−0.610, p=0.004), were identified as having significant impact on the fouling propensity of fresh SFDMs. Besides statistical analysis, more detailed experimental evidences were obtained by directly examining the identified important properties of fresh and initially fouled SFDMs. Sludge deposition during SFDM formation appears to be dominated by permeate drag force and hydrophobic interaction, whereas the subsequent fouling rate turns out to be controlled by the content of eEPS, particularly carbohydrates, which significantly correlated with viscosity and SOUR.