Forschungsprojekte
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Einfluss der Flockenzerstörung durch Belüftung im Hybridprozess Flockung / Membranfiltration auf die Freisetzung organischer Wasserinhaltsstoffe
Titel (Englisch)
Effects of floc brake-up on the degree of release of organic matter due to aeration in the hybrid process coagulation / membrane filtration
Kurzbeschreibung (Deutsch)
Kurzbeschreibung (Englisch)
The interest in membrane filtration for the direct treatment of surface water increased recently due to the extremely high water quality in respect to hygiene aspects, documented by a growing number of membrane treatment facilities, research projects and pilot plant trials worldwide. A direct treatment of surface water with ultra- or microfiltration (UF and MF) requires the dosing of coagulants, e.g. iron or aluminium salts, to achieve a stable operation of the membrane process. Otherwise, the membrane process becomes inifficient by time due to considerable fouling and scaling effects on the membrane surface by adsorption and coating layer formation caused by water contaminants. The intention of the combination of an optimised coagulation and flocculation step prior to membrane filtration is that undesired water contaminants, i.e. particles and especially organic matter like humic substances etc., should be embedded into the formed flocs and retained by the subsequent membrane filtration step. Furthermore, it is assumed that those undesired water contaminants cannot adsorb onto the membrane surface, but be eliminated extensively from the membranes surface together with the flocs using an optimised backwashing procedure. In submerged capillary membrane systems, the performance limiting effects of adsorption and layer formation are further reduced by dosing air into the filtration tank during operation and backwashing, achieving a kind of fluidised bed of the flocs around the membrane capillaries. This leads to an increased shear stress in the vicinity of the membrane capillaries due to the two phase flow of air and water, inhibiting the flocs to form coating layers on the membrane surface.
However, it could be observed by floc size measurements that a drift of the floc size distribution to smaller sized flocs may take place if air is dosed during operation into the filtration tank, assuming a floc brake-up due to the increased shear stress acting on the flocs. Additionally, indications are given that this floc brake-up will lead further to a release of the prior embedded undesired water contaminants, especially to the release of dissolved organic matter, which may be of high disadvantage for following treatment steps like activated carbon processes. Furthermore, dissolved organic substances like humics are known to be precursors for the formation of noxious disinfection by products (DBP) in disinfection steps by chlorination.
However, it could be observed by floc size measurements that a drift of the floc size distribution to smaller sized flocs may take place if air is dosed during operation into the filtration tank, assuming a floc brake-up due to the increased shear stress acting on the flocs. Additionally, indications are given that this floc brake-up will lead further to a release of the prior embedded undesired water contaminants, especially to the release of dissolved organic matter, which may be of high disadvantage for following treatment steps like activated carbon processes. Furthermore, dissolved organic substances like humics are known to be precursors for the formation of noxious disinfection by products (DBP) in disinfection steps by chlorination.
Zeitraum
06/2005 - 08/2005
Art der Finanzierung
Drittmittel
Projektleiter
- Herr Prof. Dr.-Ing. Wolfgang Uhl
Projektmitarbeiter
- Frau Dipl.-Ing. Susanne Müller
- Herr Dr.-Ing. André Lerch
Weitere Mitarbeiter (außerhalb des Lehrstuhls)
Katherine Zodrow, Civil- and Environmental Engineering, Rice University, Houston, Texas, USA
Finanzierungseinrichtungen
- DAAD Programm: - Research Internships in Science and Engineering (Rise)
Kooperationspartnerschaft
international
Website zum Projekt
Relevant für den Umweltschutz
Nein
Relevant für Multimedia
Nein
Relevant für den Technologietransfer
Nein
Berichtsjahr
2005