In this study, Smiles?? sorptivity-diffusivity numerical analysis is demonstrated to offer a comprehensive description of dead-end constant-pressure compressible cake filtration for water treatment. In addition to providing an insight on filtration performance and cake behaviour in terms of cake hydraulic permeability and compressibility in good agreement with the results derived using Ruth??s conventional cake filtration theory, the sorptivity-diffusivity model can be used to gain further information on depth-dependent local cake properties and extend our knowledge on the effect of feed suspension conditions (including solution composition, coagulant dosage and mixing) on the characteristics of the particulate assemblages (including size, structure and strength). Feed suspension conditions and primary particle properties exert significant effect on the characteristics of particles in suspensions and the resultant particulate assemblages. In the non-coagulated latex systems, an increase in ionic strength resulted in a suppression of the electric double layer of latex particles as indicated by a significant drop in the zeta potential of the feed suspension which lead to a dramatic reduction in cake hydraulic permeability. In the non-coagulated montmorillonite systems, feed suspensions with high ionic strength (1 M Na+, 50 mM Ca2+ and 50 mM Fe2+) were associated with larger suspended solids which appeared to form assemblages with nematic structures that are denser yet more permeable when compared to those with low ionic strength (0.1 M Na+, 1 mM Ca2+ and 2 mM Fe2+) which appeared to form highly ??cross-linked?? voluminous honeycomb type gel of very low permeability. Pre-coagulation of latex and montmorillonite suspensions with Al-based coagulants (alum and ACH) both resulted in formation of very large flocs which subsequently formed highly permeable solid assemblages. In the latex systems, the ratio of optimal alum to ACH dose was approximately 5:1 on a total coagulant mass basis and 1.3:1 as Al while the ratio of optimal alum to ACH dose was as high as 22:1 on a total coagulant mass basis and 6:1 as Al in the montmorillonite systems. Although both alum and ACH resulted in comparable filtration performances, the distinction in Al concentration and results of local cake properties analysis indicated the presence of different cake structures presumably due to the formation of different Al species.
| Identifer | oai:union.ndltd.org:ADTP/257853 |
| Date | January 2008 |
| Creators | Santiwong, Suvinai Rensis, Civil & Environmental Engineering, Faculty of Engineering, UNSW |
| Publisher | Publisher:University of New South Wales. Civil & Environmental Engineering |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://unsworks.unsw.edu.au/copyright, http://unsworks.unsw.edu.au/copyright |
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