Performance of Submerged Aerated Biofilters for Wastewater Treatment and Excess Biological Sludge Production

Document Type : Research Paper


1 PhD Student of Water Resources and Environmental Engineering, Department of Civil Engineering, Iran University of Science and Technology

2 Assistant Prof., Department of Civil Engineering, Iran University of Science and Technology


Minimizing sludge production in the treatment facility is a reasonable measure to reduce waste in sewage treatment, especially as regards excess biological sludge. In this regard, submerged aerated filters' (SAFs) have recently found increasing applications in treatment facilities. Thanks to their treatment mechanism, they have greatly contributed to reduction of waste production and, thereby, to reduced treatment costs. Biomass growths of both attached and suspended types take place in these filters. However, little attention has been paid to suspended sludge production and to its relationship with the physical properties of the filter. The design and application criterion for these filters is the organic loadings on unit of area or unit of volume of the media used in these filters. In this study, four filters with different physical properties and different specific areas were loaded with synthetic wastewater made of low-fat dry milk powder for five different hydraulic retention times to evaluate excess sludge production rates in submerged aerated filters. It was shown that increasing specific area increased SCOD removal efficiency up to a maximum level in saturated growths after which point the removal efficiency remained unchanging or decreased. The results also revealed that decreased hydraulic retention times increased sludge production rates in all the study columns and that media with higher porosity levels produced less excess sludge despite lower pollutant removal efficiency.


1-Rusten, B. (1984). “Wastewater treatment with aerated submerged biological filters.”
J. WPCF, 56 (5), 424-430.
2- Kennedy, K. J., and Droste, R. L. (1987). “Kinetics of down flow anaerobic attached growth reactors.” J. WPCF, 59 (4), 212-221.
3- Song, Ki-Ho. (1986). “Media design factors for fixed-bed filters.” J. WPCF, 58 (2), 115-121.
4- Charmot, C., and Marie, L. (1999). “Nitrification of high strength ammonium wastewater in an aerated submerged fixed-bed filters.” J. of Environmental Progress, 18(2), 123-129.
5- Martin, M.J., and Logan, B.E. (1996). “Scaling bacterial filtration rates in different sized porous media.” J. Environmental Engineering, 122 (5), 407-415.
6- Benthack, C., and Bonvin, D. (2001). “An optimal strategy for fixed-bed bioreactors used in wastewater treatment.” J. of Biotechnology and Bioengineering, 72 (1), 34-40.
7- Xing, C. H., and Wu, W. Z. (2003). “Excess sludge production in membrane bioreactors: A theoretical investigation.” J. of Environmental Engineering, 129 (4), 291-297.
8- Lin, H., Ong, S.L., and Wun, J. (2004). “Performance of a biofilm airlift suspension reactor for synthetic wastewater treatment.” J. of Environmental Engineering, 130 (1), 26-36.
9- Tchobanoglous, G. (2003). Wastewater engineering, Metcalf and Eddy, Inc., 959-961.
10- Clescerl, L. S., and Greenberg, A.E. (1999). Standard methods for the examination of water and wastewater, American Public Health Association, American Water Works Association, Water Environment Federation.