Anaerobic mesophilic digestion of sludge with extra-thermophilic and high ph pre-treatment


  • Anne Menert Linnéuniversitetet
  • Ergo Rikmann Linnéuniversitetet
  • Merje Michelis Linnéuniversitetet
  • Tarmo Vaalu Linnéuniversitetet
  • Viktoria Blonskaja Linnéuniversitetet
  • Raivo Vilu Linnéuniversitetet



Anaerobic; Digestion; Extra-thermophilic; High pH; Mesophilic; Pre-treatment; Sludge.


In this study different methods of sludge pre-treatment with elevated temperatures and
pH have been selected for investigation. Five sets of sludge samples were pretreated as
follows: heating at 70°
C for 30 min, at 80°
C for 20 min, at 90°
C for 10 min, at 100°
C for
5 min and NaOH-treatment (pH 12 for 4 hours). For comparison a sample from Tallinn
(3:1 mixture of primary (dry solids 5.2%) and activated sludge (dry solids 0.5%))
was used. Extra-thermophilic pre-treatment increased the degree of hydrolyses of sludge,
enabling the following anaerobic digestion process to proceed faster than that of raw
sludge. However, extra-thermophilic pre-treatment was insufficient for removal of
nitrogen and phosphorous. Nitrogen can be easily solubilized during extra-thermophilic
pre-treatment but solubilization of phosphorous occurs only through digestion. The
production of biogas during anaerobic digestion was also dependant on the quality of the
input of pre-treated sludge. The highest cumulative volume of biogas (124 mUg COD
added) was achieved by pre-treatment at 80°C. The percentage of mineralization of pretreated sludges on mesophilic digestion was the highest with 90°
C sample - 65.9%.


Metrics Loading ...


Vlyssides, A.G., Karlis, P.K., 2004, Thermal-alkaline solubilization of waste activated sludge as a pre-treatment stage for anaerobic digestion. Biores. Technol. 91 (2), 201-206.

Blonskaja, V., Menert, A., Vaalu, T., Vilu, R., 2002, Anaerobic mesophilic digestion of sludge with pre-treatment. 3rd International Symposium Anaerobic Digestion of Solid Wastes. 18-20 September 2002, Munich/Garching, Germany, 8 pp.

Blonskaja, V., Vaalu, T., 2002, Single and two-stage anaerobic mesophilic sludge digestion with thermal pre-treatment. ESWA 2002, World Environment Congress and Exhibition, Istanbul, Turkey, 8-11 July 2002. In: Appropriate Environmental and Solid Waste Management and Technologies for Developing Countries, vol 3, pp. 1463-1470.

Menert, A., Blonskaja, V., Vaalu, T., Sokk, O., Molder, H. (2001). Comparison of physical and chemical pre-treatment methods for excess sludge. 9th World Congress Anaerobic Digestion 2001. Anaerobic Conversion for Sustainability. Antwerpen, Belgium, 2-6 September 200 l. Conference Proceedings, part l, pp. 61-66.

Kim, J., Park, C., Kim, T.-H. , Lee, M., Kim, S., Kim, S.-W., Lee, J., 2003, Effects of various pre-treatments for enhanced anaerobic digestion with waste activated sludge. J. Bioscience and Bioengineering. 95(3), 271-275.

Gavala, H. N., Yenal, U., Skiadas, I.V., Westermann, P., Ahring, B.K., 2003, Mesophilic and thermophilic anaerobic digestion of primary and secondary sludge. Effect of pre-treatment at elevated temperature. Wat. Res. 37, 4561-4572.

Kepp, U., Machenbach, I., Weisz, N. and Solheim, O.E., 1999, Enchanced stabilization of sewage sludge through thermal hydrolysis - three years of experience with full-scale plant. Wat. Sci. Tech., 42(9), 89-96.

Lafitte-Trouque, S., Forster, C.F., 2002, The use of ultrasound and y-irradiation as pre-treatments for the anaerobic digestion of waste activated sludge at mesophilic and thermophilic temperatures. Biores. Technol. 84, 113-118

Gonze, E., Pillot, S., Valette, E., Gonthier, Y., Bemis, A., 2003, Ultrasonic treatment of an aerobic activated sludge in a batch reactor. Chem. Eng. Proc. 42, 965-975.

Rajan, R.V., Lin, J.G., Ray, B.T., 1989, Low-level chemical pre-treatment for enhanced sludge solubolization. J. Water Pollut. Contr. Fed. 61 (11/12), 1678-1683.

Standard Methods for the Examination of Water and Wastewater. American Public Health Association. 19th Edition, 1995.

Doyle, J.D. Parsons, S.A., 2002, Struvite formation, control and recovery, Wat. Res. , 36, 3925-3940.

Martins, S.I.F.S., 2003, Unravelling the Maillard reaction network by multiresponse kinetic modelling. PhD Thesis, Wageningen University, The Netherlands, 170 pp. ISBN:90-5808-823-5

Mata-Alvarez, J., Mace, S. , Llabres, P., 2000, Anaerobic digestion of organic solid wastes. An overview of research achievements and perspectives, Biores. Techno/., 74, 3-16.