Technical and Economic Evaluation of the Use of Variable Speed Pumps in the Backwashing of Rapid Sand Filters (A Case Study)

Document Type : Research Paper

Authors

1 MSc Student of Civil and Water & Wastewater Eng., Faculty of Water & Environment, Abbaspour College of Technology, Shahid Beheshti University, Tehran

2 Assist. Prof. of Civil and Water & Wastewater Eng., Faculty of Water & Environment, Abbaspour College of Technology-Shahid Beheshti University, Tehran

Abstract

It is observed that physical changes in the filter as bed media size variation, nozzle breakage, or water temperature variations lead to changes in the backwash regime throughout the year. The remedy proposed in this article is to use variable speed pumps in order to maintain a constant and steady optimum regime. In this study, experiments were performed using a full-scale single-layer rapid sand filter to find the optimum bed expansions of 7-8%. In addition, previous research has shown that air and backwash water flows need to be slowly and gradually increased to the optimum design values in order to avoid sand boil. In a typical treatment plant, this is normally controlled by globe valves, which results in the waste of energy and variation in pump and blower pressures. Application of variable speed pumps has the advantage that a constant pressure can be maintained throughout to yield an optimum backwash regime. Variable speed pumps provide various backwash regimes which enable design engineers and water plant operators to determine the optimum expansion in sand bed filters. This range of optimum bed expansion was found to lead to such improvements as shorter filter ripening, reduced effluent turbidity to levels below 0.3 NTU, conservation of backwash water by up to 15‒20%, and savings in backwash pump power consumption by up to 30-50%.

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References

ABB, 2013, Application guide NO.2 using variable speed drives (VSDs) in pump applications, 1st Ed., Andrademax, Zurich.
Amburgey, J.E., 2004, "Optimization of the extended terminal subfluidization wash (ETSW) filter backwashing procedure", Water Research, 39(11), 314-330.
Amburgey, J.E., Amirtharajah, A., Brouckaert, B.M. & Spivey, N.C., 2003, "An enhanced backwashing technique for improved filter ripening", J. Am. Water Works Assoc, 95 (12), 81-94.
Amirtharajah, A. & Wetstein, D.P., 1980, "Initial degradation of effluent quality during filtration", Am. Water Works Assoc, 72 (10), 518-524.
Bhargava, D.S. & Ojha, C.S.P., 1989, "Theoretical analysis of backwashtime in rapid sand filters", Water Research, 23(5), 581-587.
Bucklin, K., Amirtharajah, A. & Cranston, K.O., 1988, The characteristics of initial effluent quality and its implications for the filter to waste procedure, 1st Ed., American Water Works Association Research Foundation, Denver.
Cleasby, J.L., Dharmarajah, A.H., Sindt, G.L. & Baumann, E.R., 1989, Design and operation guidelines for optimization of the high-rate filtration process: Plant survey results, 1st Ed., American Water Works Association Research Foundation, Denver.
Cleasby, J.L., Sindt, G.L., Watson, D.A. & Baumann, E.R., 1992, Design and operation guidelines for optimization of highrate filtration process: Plant demonstration studies, 1st Ed., American Water Works Association Research Foundation, Denver.
Colton, J.F., Hillis, P. & Fitzpatrick, C.S.B., 1996, "Filter backwash and start-up strategies for enhanced particulate removal", Water Research, 30 (10), 2502-2507.
Cranston, K.O. & Amirtharajah, A., 1987, "Improving the initial quality of a dual-media filter by coagulants in the backwash", J. Am. Water Works Assoc., 79 (12), 50-63.
Fazeli, M., 2009, Pumps and pumping station design, 1st Ed., Abbaspour, Tehran. (In Persian)
Huck, P.M., Finch, G.R., Hrudey, S.E., Peppler, M.S., Amirtharajah, A., Bouwer, E.J., Albritton, W.L. & Gammie, L., 1998, Design of biological processes for organics control, 1st Ed., American Water Works Association Research Foundation, Denver.
Iran National Standard, 2007, Guidelines for quality control in water treatment plants, No. 318. (In Persian)
Logsdon, G.S., Hess, A.F., Chipps, M.J. & Rachwal, A.J., 2002, Filter maintenance and operations guidance manual, 1st Ed., American Water Works Association Research Foundation, Denver.
Mcglohorn, G., 2003, Filter assessment manual, 1st Ed., South Carolina Department of Health and Environmental Control (DHEC), Columbia.
Mehrabadi, R. A., 2005, Coagulation and flocculation in water treatment, 1st Ed., Abbaspour University, Tehran. (In Persian)
Mehrabadi, R. A., Razeghi, N., Turabian, A. & Mobedi, I., 2004, "Effect of primary filter ripening period on efficiency of Giardia cyst removal and present a method for improving", Journal of Environmental Studies (JES), 30(33), 61-68. (In Persian)
Mehrabadi, R. A., Razeghi, N., Turabian, A. & Mobedi, I., 2004, "Need to review national standard output water turbidity from water treatment plant", Journal of Environmental Studies (JES), 30(35), 61-68. (In Persian)
Qasim, S.R., Motley, E.M. & Zhu, G., 2000, Water works engineering: Planning, design and operation, 1st Ed., Prentice Hall, New Jersey.
Susumu, K., 2000, Integrated design and operation of water treatment facilities, 2nd Ed., Wiley, New York.
Taebi, A. & Chamani, M.R., 2006, Water distribution systems, 2nd Ed., Isfahan University of Technology, Isfahan. (In Persian)
United States Environmental Protection Agency, 1998, Optimizing water treatment plant performance using the composite correction program, 1st Ed., USEPA

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