The Effect of Mixing Rate on Performance of Anaerobic Reactor in Methane Production

Document Type : Original Article


1 Department of Mechanical Engineering, Faculty of Mechanical Engineering, University of Guilan, Rasht, Iran

2 Department of Chemical Engineering, Faculty of Engineering, University of Guilan, Rasht, Iran


In this study, a mathematical model was used to predict the dynamic behaviour of the system under conditions of imperfect mixing in an Anaerobic Digestion (AD) process. To evaluate the system performance, the effect of mixing parameters by calculating the quantities of methane gas produced, system power, and effluent quality was investigated. Numerical results showed that with an increase in the mixing rate (α) by 20%, methane production rate, power production, and the effluent COD removal efficiency of the system increased by 19%, 19% and 12%, respectively. At an equal mixing rate, the amount of methane produced in influent with a concentration of 12.1% was 4.5 times higher than the influent with a concentration of 2.5%, while no significant change was observed in the effluent quality. Additionally, it was found that the mixing rate effect is more important than the mean cell retention time in the anaerobic reactor. The best fitted correlations for methane production rate and effluent COD removal efficiency using regression analogy at different organic loads of wastewater are presented.


  1. Kumar Ghosh, S. and Mandal, S. 2018. “Evaluation of Biogas as an Alternative Driving Force of Electrically Operated Vehicles: A Case Study.” International Journal of Engineering, Transaction B: Applications, 31(5), pp.834–840.
  2. Aceleanu, M. I., Șerban, A. C., Pociovălișteanu, D. M. and Dimian, G. C. 2017. “Renewable energy: A way for a sustainable development in Romania.” Energy Sources, Part B: Economics, Planning, and Policy, 12(11), pp.958–963.
  3. Lindmark, J., Thorin, E., Bel Fdhila, R. and Dahlquist, E. 2014. “Effects of mixing on the result of anaerobic digestion: Review.” Renewable and Sustainable Energy Reviews, 40, pp.1030–1047.
  4. Colangiuli, S., Rodríguez, A., Sanromán, M. Á. and Deive, F. J. 2018. “Demonstrating the viability of halolipase production at a mechanically stirred tank biological reactor.” Bioresource Technology, 263, pp.334–339.
  5. Bello-Mendoza, R. and Sharratt, P. N. 1998. “Modelling the effects of imperfect mixing on the performance of anaerobic reactors for sewage sludge treatment.” Journal of Chemical Technology & Biotechnology, 71(2), pp.121–130.<121::AID-JCTB836>3.0.CO;2-7
  6. Ong, H. K., Greenfield, P. F. and Pullammanappallil, P. C. 2002. “Effect of Mixing on Biomethanation of Cattle-Manure Slurry.” Environmental Technology, 23(10), pp.1081–1090.
  7. Karim, K., Thomasklasson, K., Hoffmann, R., Drescher, S., Depaoli, D. and Aldahhan, M. 2005. “Anaerobic digestion of animal waste:  Effect of mixing.” Bioresource Technology, 96(14), pp. 1607–1612.
  8. Karim, K., Hoffmann, R., Thomas Klasson, K. and Al-Dahhan, M. H. 2005. “Anaerobic digestion of animal waste: Effect of mode of mixing.” Water Research, 39(15), pp.3597–3606.
  9. Syaichurrozi, I. and Sumardiono, S. 2014. “Effect of Total Solid Content to Biogas Production Rate from Vinasse.” International Journal of Engineering, Transaction B: Applications, 27(2), pp.177–184.
  10. Rea, J. 2014. “Kinetic Modelling and Experimentation of Anaerobic Digestion”. Bachelor Degree Thesis, U.S.A, MIT University, Massachusetts.
  11. Benali, M. 2019. “Experimental Investigation of Biogas Production from Cow Dung in an Anaerobic Batch Digester at Mesophilic Conditions.” Iranian ( Iranica ) Journal of Energy and Environment, 10(2), pp.121–125.
  12. Prasad Lohani, S. 2020. “Anaerobic Co-digestion of Food Waste with Cow Manure.” Iranian (Iranica) Journal of Energy and Environment, 11(1), pp.57–60.
  13. Ebrahimi, A. and Najafpour, G. D. 2016. “Biological Treatment Processes: Suspended Growth vs. Attached Growth.” Iranian (Iranica) Journal of Energy and Environment, 7(2), pp.114–123.
  14. Shanmugam, L., Ramalingam, V., Palaniyandi, S. and Subramanian, S. 2019. “Comparison of different mixing phenomena in anaerobic digestion using food waste and sewage treatment plant for green biofuel through simulations of velocity contours.” Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 41(18), pp.2233–2245.
  15. Zhang, J., Mao, L., Nithya, K., Loh, K.-C., Dai, Y., He, Y. and Wah Tong, Y. 2019. “Optimizing mixing strategy to improve the performance of an anaerobic digestion waste-to-energy system for energy recovery from food waste.” Applied Energy, 249, pp.28–36.
  16. Kolodynskij, V., Baltrėnas, P. and Dobele, G. 2020. “Experimental research of biogas production by using a three-stage semi-continuous bioreactor with modified mixer.” Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, pp.1–15.
  17. Ghovvati, M., Khayati, G., Attar, H. and Vaziri, A. 2016. “Kinetic parameters estimation of protease production using penalty function method with hybrid genetic algorithm and particle swarm optimization.” Biotechnology & Biotechnological Equipment, 30(2), pp.404–410.
  18. Pavlostathis, S. G. and Gossett, J. M. 1986. “A kinetic model for anaerobic digestion of biological sludge.” Biotechnology and Bioengineering, 28(10), pp.1519–1530.
  19. Vesvikar, M. S. and Al-Dahhan, M. 2005. “Flow pattern visualization in a mimic anaerobic digester using CFD.” Biotechnology and Bioengineering, 89(6), pp.719–732.
  20. Bersinger, T., Le Hécho, I., Bareille, G., Pigot, T. and Lecomte, A. 2015. “Continuous Monitoring of Turbidity and Conductivity in Wastewater Networks.” Revue des sciences de l’eau, 28(1), pp.9–17.
  21. Mucha, Z. and Kułakowski, P. 2016. “Turbidity measurements as a tool of monitoring and control of the SBR effluent at the small wastewater treatment plant – preliminary study.” Archives of Environmental Protection, 42(3), pp.33–36.
  22. Stafford, D. A. 1982. “The effects of mixing and volatile fatty acid concentrations on anaerobic digester performance.” Biomass, 2(1), pp.43–55.
  23. Tchobanoglous, G., F. L. Burton and H. D. Stensel, 2003. “Wastewater Engineering; Treatment and Reuse”. New York: McGraw Hill Inc.
  24. Fedailaine, M., Moussi, K., Khitous, M., Abada, S., Saber, M. and Tirichine, N. 2015. “Modeling of the Anaerobic Digestion of Organic Waste for Biogas Production.” Procedia Computer Science, 52, pp.730–737.
  25. Monteith, H. D. and Stephenson, J. P. 1981. “Mixing efficiencies in full-scale anaerobic digesters by tracer methods.” Journal (Water Pollution Control Federation), 53(1), pp.78–84. Retrieved from
  26. Jijai, S., Srisuwan, G., O-Thong, S., Norli, I. and Siripatana, C. 2016. “Effect of Substrate and Granules/Inocula Sizes on Biochemical Methane Potential and Methane Kinetics.” Iranian (Iranica) Journal of Energy and Environment, 7(2), pp.94–101.
  27. Ubaidah, M. A., Hilmi, S. M. H. S., Yunus, M. F. M. and Tahiruddin, S. 2016. “A Comparative Study on Biogas Production between Day and Night at Sime Darby’s Palm Oil Mill.” Iranian (Iranica) Journal of Energy and Environment, 7(2), pp.102–108.
  28. Khayati, G. and Barati, M. 2017. “Bioremediation of Petroleum Hydrocarbon Contaminated Soil: Optimization Strategy Using Taguchi Design of Experimental (DOE) Methodology.” Environmental Processes, 4(2), pp.451–461.