Density and Strength of Deposits Formed During In-line Flocculation Filtration of Secondary Effluents
The purpose of this work was to evaluate filtration efficiency by deposit characterization, applying various pretreatments during in-line flocculation filtration of secondary effluents. Shallow bed laboratory filtration columns were used. Attachment and detachment constants and deposit densities (on the basis of volume and mass of accumulated matter) of aggregates formed by effluents treated with alum, alum-anionic polymer or different cationic polymers as primary coagulants during in-line filtration, were calculated. The floc size-density relationship coefficients “a” and “b” for polydispersed primary particles were calculated and compared with some other already published coefficients which are mainly based on homogeneous particles. The calculated values for the different “a” coefficients were around 1.0. The values for the “b” coefficients were (1.15–1.45). Based on the calculated deposit densities and attachment constants, and results obtained for turbidity and TSS removal efficiencies, it was shown that filtration without any treatment caused weak deposits. 10–20 mg/l alum doses, at natural pH values of the effluents used (7.3–8.5), produced deposits of relatively low attachment strength. The deposit density for the 10 mg/l dose was higher than that for the 20 mg/l dose. High molecular weight low anionic polymers strengthened the alum-particle bond. Medium cationic, high molecular weight polymers at 0.5 mg/l and high cationic medium molecular weight polymers at 7 mg/l performed equally or better than alum as primary flocculants and formed strong deposits with low deposit densities. High cationic low molecular weight polymers were not effective at doses up to 7 mg/l probably because of the low contact time.
KeywordsPrimary Particle Effective Porosity Deposit Density Floc Size Turbidity Removal
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- Adin, A., Rebhun, M.: A Model to Predict Concentration and Head-loss Profiles in Filtration. J. AWWA. 8 (1977) 444–451.Google Scholar
- Boller, M.: Flockungfiltration zur Reinigung von Abwasser. Diss. ETH Nr. 6748, Zürich 1980.Google Scholar
- Darby, J.L.: Depth Filtration: Measurements and Predictions of Particle-particle Interactions. Ph.D. dissertation, University of Texas, 1988.Google Scholar
- Hunt, J.: The Accumulation of Solids within Deep Bed Filters. 6th World Filtration Congress, Nagoya 1993, Japan, pp. 236–239.Google Scholar
- Ives, K.J.: Theory of Filtration. IWSA Congress, Vienna 1969.Google Scholar
- Mackie, R.I.: Numerical Solution of the Filtration Equations for Polydisperse Suspensions. 6th World Filtration Congress, Nagoya 1993, Japan, pp. 244–247.Google Scholar
- Mintz, D.M.: Modern Theory of Filtration. International Water Supply Assoc, Seventh Congress Vol. 1. Special Subject No. 10, 1966.Google Scholar
- O’Melia, C.R., Ali, W.: The Role of Retained Particles in Deep Bed Filtration. Prog. Wat. Tech. 10(5/6) (1978) 167–182.Google Scholar
- Rebhun, M.: Floc Formation and Breakup in Continuous Flow Flocculation and in Contact Filtration. In: Chemical Water and Wastewater Treatment, H.H. Hahn and R. Klute (Eds.). Springer, Berlin Heidelberg New York 1990, pp. 117–126.Google Scholar
- Vigneswaran, S., Chang, J.S.: Mathematical Modeling of the Entire Cycle of Deep Bed Filtration. Wat. Air Soil Pollut. 29 (1986) 155–164.Google Scholar
- Wiesner, M.R.: Calibration et Validation d’un Model de Filtration: Application a une étude a l’echelle pilote. L’eau, L’industrie, Les Nuisances, Paris, France 112 (1987) 39–44.Google Scholar