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RESEARCH PRODUCT

The role of EPS in the foaming and fouling for a MBR operated in intermittent aeration conditions

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Abstract This work investigates the causes of foaming and fouling in an Intermittent Aerated – Membrane BioReactor (IA-MBR) used for wastewater treatment. The experiment was divided into three periods with different aerated regimes expressed with different t aeration /t cycle ratio (Period I: 60 min/180 min, Period II: 80 min/180 min, Period III: 30 min/90 min). The advanced foaming tests used allow the study of the role of extracellular polymeric substances (EPSs) on foaming and fouling. In general, in the Periods I and II, good correlations between the EPSs and the Modified Scum Index without purification (MSI 0 ) and the Foam Power were observed. The results shown that the filamentous microorganisms, which mainly grew in the Period III, play also a key factor in the foaming and fouling. In particular, when a net proliferation of filamentous bacteria occurred (during period III with a higher number of cycles per day) both EPSs concentration and filamentous abundance influence the modified scum index obtained after two purification steps (MSI 2 ). Finally, the processing data show that the EPSs hampered also the membrane filtration but improve the pre-filtration action of cake layer. On the other hand, the co-presence of EPSs and filamentous bacteria reduced the effect o cake layer as pre-filter.