Evaluation of Particles Removal Efficiency in Rapid Sand Filters by Changing Particle Concentration and Media Grain Size

Document Type : Research Paper

Authors

1 Assis. Prof. of Irrigation, College of Agriculture, Bu-Ali Sina University, Hamedan

2 Grad. Student of Irrigation and Drainage, College of Agriculture, Bu-Ali Sina University, Hamedan

3 Assis. Prof. of Soil Science, College of Agriculture, Bu-Ali Sina University, Hamedan

Abstract

Removal of particles by filter is a complex water treatment process. Several factors are involved that include shape and size of filter grains, particle concentration, filtration velocity, and filter depth. The objective of this study was to evaluate particle removal efficiency (η)  by changing particle concentration and media grain size in a rapid sand filter. Five concentrations (100, 200, 300, 400, and 500 ppm) of Kaolin particles and three mean media sizes (0.51, 1, and 1.41 mm) were used. The filter depth and the filtration velocity were 25 cm and 0.086 cmsec-1, respectively. Silica sand was used as the filter medium in all the experiments. The results showed that for the filter medium with an average grain size of 0.51 mm, removal efficiency increased with increasing influent particle concentration during the initial hours of filtration. Generally, suspended solids removal efficiency was higher at low particle concentrations. No significant differences were observed in removal efficiency for the three media sizes and particle concentrations of up to 300 mg/L, but for concentrations above 300 mg/L, removal efficiency decreased, especially for filter media with an average grain size of 1.41 mm. Removal efficiency decreased in filter media with average grain sizes of 1 and 1.41 mm at high particle concentrations from the very initial hours of filtration. The highest removal efficiency was observed in the filter medium with an average grain size of 0.51 mm. Differences in removal efficiencies between the filter media with average grain sizes of 0.51 and 1 mm were much greater than those between filter media with average grain sizes of 1 and 1.41 mm. In other words, the critical grain size for the filter medium was 1 mm. 

Keywords

References

1- Kau, S. M., and Lawler, D. F. (1995). “Dynamics of deep bed filtration: velocity, depth, and media.” Environ. Eng., 121(12), 850-859.
2- Shin, C. (2006). “Finite element simulation of deep bed filtration.” Chem. Eng. Sci., 61 (8),
2324-2329.
3- Vigneswaran, S., and Song, C. J. (1986). “Mathematical modeling of the entire cycle of deep bed filtration.” Water, Air and Soil Poll., 29 (2), 155-164.
4- Vigneswaran, S., Ngo, H. H., and Jeyaseelan, J. (1997). “Application of non-conventional filtration technologies in pollution control.” Environ. Monitoring Assess, 44 (1-3), 231-240.
5- Mackie, R. I., and Zhao, Q. (1999). “A framework for modeling removal in the filtration of poly disperse suspensions.” Wat. Res., 33(3), 794-806.
6- Vigneswaran, S., and  Thiyagaran, M. (1984). “Application of filtration theories to groundwater recharge problems.” Water, Air and Soil Poll., 22 (4), 417-428.
7- Boller, M. A., and Kavanaugh, M. C. (1995). “Particle characteristics and head loss increase in granular media filtration.” Wat. Res., 29(4), 1139-1149.
8- Han ko, C., and Elimelech, M. (2000). “The "shadow effect" in colloid transport and deposition dynamics in granular porous media: measurements and mechanisms.” Environ. Sci. Technol., 34(17), 3681-3689.
9- Jegatheesan, V., and Vigneswaran, S. (1997). “The effect of concentration on the early stages of deep bed filtration of submicron particles.” Wat. Res., 31(11), 2910-2913.
10- Qi, S. (1998). “Expression for critical suspended particle size in granular media filtration processes.” Wat. Res., 32(9), 2856-2859.
11- Chang, Y. I., and Chan, H. C. (2005). “Network simulation for deep bed filtration of Brownian particles-a supplement.” Chem. Eng. Sci., 60(10), 2827-2831.
12- Elimelech, M., and O'Melia, C. R. (1990). “Kinetics of deposition of colloidal particles in porous media.” Environ. Sci. Technol., 24(10), 1528-1536.
13- Stephan, E. A., and Chase, G. G. (2001). “A preliminary examination of zeta potential and deep bed filtration activity.” Separation and Purification Technol., 21(3), 219-226.
14- Jegatheesan, V., and Vigneswaran, S. (2000). “Transient stage deposition of submicron particles in deep bed filtration under unfavorable conditions.” Wat. Res., 34(7), 2119-2131.
15- Xu, S., Gao, B., and Saiers, J. E. (2006). “Straining of colloidal particles in saturated porous media.” Water Resource Res., 42 (12).
Journal of Water and Wastewater; Ab va Fazilab ( in persian )
Volume 19, Issue 4 - Serial Number 4
Serial number:68
January and February 2009
Pages 40-47

Files

Share

How to cite

Statistics