Membrane bioreactors (MBRs) represent by now a well established alternative for wastewater treatment.Their increasing development is undoubtedly related to the several advantages that such technology isable to guarantee. Nevertheless, this technology is not exempt from operational problems; among themthe foaming still represents an “open challenge” of the MBR ﬁeld, due to the high complexity of phe-nomenon. Unfortunately, very little work has been done on the foaming in MBRs and further studies arerequired. Actually, there is not a distinct difference between conventional activated system and MBR: themain difference is that the MBR plants can retain most Extracellular Polymeric Substances (EPSs) in thebioreactor. For these reason, unlike conventional activated sludge systems, MBRs have experiencedfoaming in the absence of foam-forming micro-organisms. Nevertheless, the actual mechanisms of EPSproduction and the role of bacteria in producing foam in activated sludge in MBRs are still unclear. In thispaper, the authors investigated the roles of EPS and foam-forming ﬁlamentous bacteria by analyzingsamples from different pilot plants using MBRs. In particular, in order to deﬁne the macroscopic featuresand the role of EPS and ﬁlamentous bacteria, a Modiﬁed Scum Index (MSI) test was applied and pro-posed. Based on the MSI and the foam power test, the causes of biological foaming were identiﬁed interms of the potential for foaming, the quality and the quantity of the foam. The results indicated that theMBR foaming was inﬂuenced signiﬁcantly by the concentration of bound EPSs in the sludge. In addition,the quantity and stability of MBR scum increased when both bound EPSs and foam-forming ﬁlamentousbacteria were present in the activated sludge.
|Numero di pagine||9|
|Rivista||Journal of Environmental Management|
|Stato di pubblicazione||Published - 2013|
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