Biological coatings on EPDM-membranes are a problem on many large wastewater treatment plants, as the oxygen supply of the micro-organisms is no longer guaranteed. Investigations prove that the pressure loss and the Shore A-hardness of the EPDM-membranes increase while on the other hand their softener content decreases accordingly. The detected coatings on the membrane surfaces and in the slits or holes of the membranes show extra-cellular organic substances (EPS), which, compared with fibrillar/filamented EPS usually found on surfaces in wastewater treatment plants, are viscous to a much greater extent. As, besides primary organic parts (carbon), the coatings on the membranes as well as in the slits or holes also consist of inorganic constituents (magnesium, silicon, and others), the authors assume that, the separating agent (and also inactive filler) talcum (magnesium silicate), used when producing the membranes, supports at least a first beginning of the coating. Superfine dust constituents and fibres, input via the compressed air, will build up inside the coating and consequently lead to a gradual clogging of the holes or slits. Besides chemical cleaning measures, the exchange of the EPDM-membranes against membranes of silicone would also be a possible measure to solve this problem. The market will decide, if, in the future, a cleaning or an exchange of the EPDM-membranes against membranes of silicone will be applied, but it has to be considered that the loss of softener is irreversible.
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Research Article| October 01 2004
Biological coating of EPDM-membranes of fine bubble diffusers
R. von Hoessle
R. von Hoessle
1Associate professor, Institut WAR, Technische Universität Darmstadt, Petersenstrasse 13, 64287 Darmstadt, Germany
*Entsorgungsbetriebe der Landeshauptstadt Wiesbaden, Unterer Zwerchweg 120, 65205 Wiesbaden, Germany
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Water Sci Technol (2004) 50 (7): 79–85.
M. Wagner, R. von Hoessle; Biological coating of EPDM-membranes of fine bubble diffusers. Water Sci Technol 1 October 2004; 50 (7): 79–85. doi: https://doi.org/10.2166/wst.2004.0421
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