Influence of Alum Coagulant Dose and Influent Turbidity on Floc Blanket Growth Rate, Steady-State Suspended Solids Concentration, and Turbidity Removal
Publication: Journal of Environmental Engineering
Volume 143, Issue 2
Abstract
Floc blankets are concentrated, fluidized beds of particles utilized in some water treatment plants. Floc blankets occur in vertical-upflow sedimentation tank configurations and are reported to enhance removal of suspended solids. In this research, floc blankets were formed in the laboratory at an upflow velocity of and at varying alum coagulant dosages with influent turbidities of 10 nephelometric turbidity units (NTU), 100 NTU, and 500 NTU. Image analysis was utilized to quantify floc blanket suspended solids concentration and floc-water interface height over time. Blankets formed with higher influent turbidities required a lower ratio of coagulant dose to influent turbidity, formed more quickly, had higher steady-state suspended solids concentrations, and achieved better suspended solids removal efficiency. Increasing alum coagulant dose decreased steady-state floc blanket suspended solids concentration and resulted in lower effluent turbidities. At an influent turbidity of 100 NTU, effluent turbidity was strongly correlated with coagulant dose at coagulant doses of 1 to alum. Diminishing improvement in turbidity removal was observed for coagulant doses above alum for both 100 and 500 NTU. A higher ratio of coagulant dose to influent turbidity could be used by water treatment plant operators to allow floc blankets to form quickly, and after formation of the floc blanket, the coagulant dose could be reduced without significant impact on the removal of suspended particles.
Get full access to this article
View all available purchase options and get full access to this article.
References
Bache, D. H. (2010). “Model of dynamic and macroscopic features of a floc blanket.” Aqua J. Water Supply Res. Technol., 59(1), 53–65.
Casey, J. J., O’Donnel, K., and Purcell, P. J. (1984). “Uprating sludge blanket clarifiers using inclined plates.” Aqua, 2(1), 91.
Chen, L., Lee, D.-J., and Chou, S.-S. (2006). “Charge reversal effect on blanket in full-scale floc blanket clarifier.” J. Environ. Eng., 1523–1526.
Chen, L. C., et al. (2002). “Observations of blanket characteristics in full-scale floc blanket clarifiers.” Water Sci. Technol., 47(1), 197–204.
City of Ithaca. (2011). Drinking water quality report, Ithaca, New York.
Gould, B. (1969). “Sediment distribution in upflow.” Aust. Civ. Eng., 10(9), 27–29.
Gregory, R. (1979). “Floc blanket clarification.”, Water Research Centre, Swindon, U.K.
Hurst, M., Weber-Shirk, M. L., and Lion, L. W. (2010). “Parameters affecting steady-state floc blanket performance.” J. Water Supply Res. Technol. Aqua, 59(5), 312–323.
Hurst, M. W., Weber-Shirk, M. L., Charles, P., and Lion, L. W. (2014). “An apparatus for observation and analysis of floc blanket formation and performance.” J. Environ. Eng., 11–20.
Jarvis, P., Jefferson, B., Gregory, J., and Parsons, S. A. (2005). “A review of floc strength and breakage.” Water Res., 39(14), 3121–3137.
LabVIEW [Computer software]. National Instruments, Austin, TX.
Lin, W., et al. (2004). “Treating high-turbidity water using full-scale floc blanket clarifiers.” J. Environ. Eng., 1481–1487.
Miller, D. G., and West, J. T. (1968). “Pilot plant studies of floc blanket clarification.” AWWA J., 60(2), 154–164.
Mohammadi, M. S. (2002). “A generalized refractive index equation for estimating the average particle size in colloidal suspensions.” J. Dispersion Sci. Technol., 23(5), 689–697.
Reynolds, T. D., and Richards, P. A. (1996). Unit operations and processes in environmental engineering, PWS Publishing, Boston.
Schulz, C. R., and Okun, D. A. (1984). Surface water treatment for communities in developing countries, Wiley, New York.
Sung, S., Lee, J., and Wu, R. (2005). “Steady-state solid flux plot of blanket in upflow suspended bed.” J. Chin. Inst. Chem. Eng., 36(4), 385–391.
Tchobanoglous, G., Burton, F. L., and Stensel, D. H. (2003). Wastewater engineering treatment and reuse, McGraw-Hill, New York.
Tse, I. C., Swetland, K., Weber-Shirk, M. L., and Lion, L. W. (2011). “Fluid shear influences on the performance of hydraulic flocculation systems.” Water Res., 45(17), 5412–5418.
Weber-Shirk, M. L. (2008). “An automated method for testing process parameters.” 〈http://confluence.cornell.edu/display/AGUACLARA/Process+Controller+Background〉 (Apr. 5, 2012).
Zhang, Z., et al. (2006). “Performance of a novel vertical-flow settler: A comparative study.” J. Environ. Sci., 18(5), 858–863.
Information & Authors
Information
Published In
Journal of Environmental Engineering
Volume 143 • Issue 2 • February 2017
Copyright
© 2016 American Society of Civil Engineers.
History
Received: Jan 13, 2015
Accepted: Feb 22, 2016
Published online: Aug 19, 2016
Discussion open until: Jan 19, 2017
Published in print: Feb 1, 2017
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.