Thermophilic Aerobic Digestion of Activated Sludge; Reduction of Solids and Pathogenic Microorganisms

Document Type: Research Note


1 Biotechnology Group, Department of Chemical Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran, I.R. IRAN

2 Department of Biochemical Engineering and Biotechnology,Indian Institute of Technology (I.I.T.), Hauz Khas, 110016, New Delhi, INDIA


In the temperature range of 10 to 80 ºC and in a batch digester, a typical activated sludge was digested aerobically. Reaction rate constants were determined by measuring the amounts of volatiles removed from the suspended solids at different time intervals during the process. The maximum value of the reaction rate constant (0.45 d-1) occurred in the temperature range of 55-60˚C. Removal of indicator organisms (pathogens) in the sludge, during the batch digestion, was also studied. Sludge digestion at 60 ºC provided a noticeable difference in reduction of the indicator organisms as compared to digestion carried out at 55 ºC. Optimum thermophilic aerobic digestion for high rate removal of volatile suspended solids and effective inactivation of pathogens happened in temperature range of 60-65 ºC.


Main Subjects

[1] Lapara, T. M. and Alleman, J.E., Thermophilic aerobic biological wastewater treatment, Wat. Res., 33 (4), 895 (1999).
[2] Murthy, S.N., Novak, J.T., Holbrook, D.R., and Surovik, F., Mesophilic aeration of autothermal thermophilic aerobically digested biosolids to improve plant operations, Wat. Environ. Res., 72 (4), 476 (2000).
[3] Kelly, H.G., P.Eng., Dayton & Knight LTD., and Mavinic, D.S., Autothermal thermophilic aerobic digestion research, application and operational experience, Weftec Workshop W104, thermophilic digestion, Los Angeles convention center, California (2003).
[4] Kabrick, R. M. and Jewell, W. J., Fate of pathogens in thermophilic aerobic sludge digestion, Wat. Res., 16, 1051 (1982).
[5] Hamer, G., and Zwiefelhofer, H.P., Aerobic thermo-philic hygienisation: A supplement to anaerobic mesophilic waste sludge digestion. Chem. Eng. Res. Des., 64, 417 (1986).
[6] Bomio, M., Sonnleitner, B., and Fiechter, A., Growth and biocatalytic activities of aerobic thermophilic populations in sewage sludge, Appl. Microbiol. Biotech., 32, 356 (1989).
[7] Mason, C. A., Häner, A. A., and Hamer, G., Aerobic thermophilic waste sludge treatment, Wat. Sci. Tech.,  25 (1), 113 (1992).
[8] Pagilla, K. R., Crancey, K. C., and Kido, W. H., Aerobic thermophilic pretreatment of mixed sludge for pathogen reduction and Norcardia control, Wat. Environ. Res., 68, 1093 (1996).
[9] Watanabe, H., Kitamura, T., Ochi, S., and Ozaki, M., Inactivation of pathogenic of bacteria under mesophilic and thermophilic conditions, Wat. Sci. Tech., 36 (6-7), 25 (1997).
[10] Brock, T.D., “General, Molecular, and Applied Micro-biology”,Brock, T. D., Ed., John Wiley and Sons, New York, Introduction (1986).
[11] Fujio, Y. and Kume, S., Isolation and identification of thermophilic bacteria from sewage sludge compost, J. Ferment. Bioengng., 72 (5) 334 (1991).
[12] Smith, J. E., Young,  K. W.  and  Dean,  R. B., Biological oxidation and disinfection of sludge, Wat. Res., 9, 17 (1975).
[13] APHA, AWWA, WEF., “Standard Methods for the examination of water and wastewater”, American Public Health Association, 18th Ed., Washington D.C. (1992).
[14] Eckenfelder,  W. W. Jr.,  Studies on  the  oxidation kinetics of biological sludges, Sewg. Ind. Wks., 28, 983 (1956).
[15] Bhargava,  D. S.  and Datar,  M. T., Progress  and kinetics of aerobic digestion of secondary sludges, Wat. Res., 22(1), 37 (1988).
[16] Randall,  C. W., Richards, J. B.,  and  King, P. H., Temperature effects on aerobic digestion kinetics, J. Environ. Engng. Div., ASCE., 101, 795 (1975).
[17] Matsch, L.C. and Drnevich, R.F., Autothermal aerobic digestion, J. WPCF., 49 (2), 296 (1977).