Improved removal of particles during the treatment of natural aquatic suspensions has been achieved by pre-ozonation and the addition of small quantities of iron salts (βFe ≤ 0.1 mg.L-1; “Fe(III)-assisted filtration”) followed by rapid filtration. As shown by investigations on a large-scale installation at Lake Constance Water Supply, this procedure reliably reduces suspended solids by at least 2-3 powers of ten in long-term use. However, the high efficacy of Fe(III)-assisted filtration cannot be explained on the basis of known coagulation mechanisms (like adsorption-charge neutralization, co-precipitation). Instead, the essential step was found to be the conditioning of the filter medium by coating it with colloids containing Fe(OH)3, and this “Fe coating” process occurs only in the presence of alkaline earths (especially Ca2+). According to further experiments, the enhanced solid-liquid separation was ultimately traced to chemical interactions such as the formation of calcium-organic association structures between the iron hydroxides and other solids. For design of Fe(III)-assisted filtration steps, finally, a βCa/DOC ratio above 40 mg.mg-1 and pre-oxidation with ozone dosages not exceeding 2 mg O3/mg DOC was recommended.
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April 01 2002
Investigations on the filtration of natural aquatic suspensions supported by dosing small amounts of Fe(III)-salts (βFe ≤ 0.1 mg.L-1): mode of action and basic design criteria Available to Purchase
R. Winzenbacher;
*GELSENWASSER AG, Department of Planning, Maintenance, Plant Construction, Willy-Brandt-Allee 26, D-45891 Gelsenkirchen, Germany. (at present: Zweckverband Landeswasserversorgung, Water Control and Research Laboratory, D-89123 Langenau, Germany. (E-mail: [email protected]))
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R. Schick;
R. Schick
**Zweckverband Bodensee-Wasserversorgung, Water Control and Research Laboratory, Süflenmühle, D-78354 Sipplingen, Germany. (E-mail: [email protected]; [email protected])
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H.-H. Stabel;
H.-H. Stabel
**Zweckverband Bodensee-Wasserversorgung, Water Control and Research Laboratory, Süflenmühle, D-78354 Sipplingen, Germany. (E-mail: [email protected]; [email protected])
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M. Jekel
M. Jekel
***Technical University of Berlin, Institute of Environmental Technology, Department of Water Quality Control, Strafle des 17. Juni 137, D-10623 Berlin, Germany. (E-mail: [email protected])
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Water Supply (2002) 2 (2): 91–98.
Citation
R. Winzenbacher, R. Schick, H.-H. Stabel, M. Jekel; Investigations on the filtration of natural aquatic suspensions supported by dosing small amounts of Fe(III)-salts (βFe ≤ 0.1 mg.L-1): mode of action and basic design criteria. Water Supply 1 April 2002; 2 (2): 91–98. doi: https://doi.org/10.2166/ws.2002.0050
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