Behavior of Membrane Scaling During Crossflow Filtration in the Anaerobic MBR System

Membrane autopsy to investigate CaCO3 scale formation in pilot‐scale, submerged membrane bioreactor treating calcium‐rich wastewater

“…The MBR typically contained higher CO 2 partial pressure than that in an aerobic MBR (about 30% vs. 0.03%), which may lead to higher potential for CaCO 3 scaling due to high concentration of carbonate ions. 2 However, in the present study, CaCO 3 scaling was also found to be significant in the submerged, aerobic MBR. These results confirmed that the rejection of calcium should be enhanced considerably (more than 90%) by the formation of CaCO 3 scaling on the MF membrane surface when applied to treat calcium-rich wastewater in which the LSI value is high and positive.…”

“…2 Based on the measurement of calcium concentration in the eluate in this study, however, the addition of citric acid solution prior to NaOCl solution was less efficient in the removal of CaCO 3 scaling than applying the sequence NaOCl-citric acid solution. These current results suggest that the order sequence of chemical cleaning needs to be evaluated to determine optimal cleaning strategies for removing membrane scaling in submerged MBR.…”

“…The importance of inorganic scaling on the surface of membranes has been investigated previously in submerged MBR treating synthetic wastewater. 2,22 However, solid evidences that calcium can contribute to internal fouling has been lacking. T-EDXA in the cross-sectional direction of fouled membrane (indicated as position 5) demonstrates that the predominant component within membranes is fluoride, not calcium, although local observations using microscopic techniques may not be representative of the full morphological characteristics inside membranes.…”

“…Calcium in the form of Ca +2 interacts with alkalinity and forms CaCO 3 leading to sludge displacement and membrane scaling. 2 Given that the concentrations of dissolved inorganic solutes increase in the direction of the feed flow, the concentrations of sparingly soluble salts exceeds their solubility limit. Crystallization may occur either directly on the membrane surface or in the bulk and subsequently deposit on the membrane.…”

“…1 Higher biomass concentration in the MBR results in a smaller footprint and excellent effluent quality, thereby enabling many wastewater treatment applications without further treatments. 2,3 Although there has been an upsurge of interest in MBRs for the treatment of wastewater, the occurrence of membrane fouling caused by deposition of foulants on the membrane surface and/or foulant adsorption within the membrane pores is a major problem of this innovative technology. Membrane fouling results in poor membrane performance by decreasing the specific permeate flux and subsequently increasing capital and operational costs.…”