Mixing effect on bio-methanation, settleability and dewaterability in the anaerobic digestion of sewage sludge fractions

Biomethanation and dewaterability characteristics of primary sludge (PS), secondary sludge (SS) and mixed sludge (MS) fractions were assessed after anaerobic stabilization under parallel batch and continuous mixing conditions at 35℃ in order to investigate the performance of the separate digestion system. Similar methane conversion/yield values were obtained in PS, SS and MS digestion with continuous mixing’s positive effect only in PS digestion. Continuous mixing resulted in 50% increase in the methane yield (600(+/-100) mL/g VSadd.d. SS digestion produced a comparable methane yield at 650(+/-100) mL/g VSadd.d showing no effect due to mixing pattern. Settling and dewaterability characteristics of the stabilized PS were superior to stabilized SS samples. A reverse relationship was obtained between settling and dewaterability characteristics where intermittent mixing enhanced settling ability while continuous mixing resulted in higher dewaterability of the stabilized sludges. Polyelectrolyte (PE) addition showed a negative effect on the settleability of the sludges. Low degree mixing resulted in 50% sludge volume reduction and an SVI of 64 mL/g VS compared to 25% volume reduction and 82 mL/g SVI in the continuous mixing mode for the stabilized PS. A similar trend for the stabilized SS but weaker values with 25% volume reduction and an SVI 182 mL/g in the intermittent mixing mode compared to 15% volume reduction and 200 mL/g VS SVI indicated a much lower settleability in the continuous mixing mode and compared to stabilized PS.

Keywords:

Anaerobic digestion, biosolids, dewaterability, mixing settleability, sewage sludge,

PDF

___

G. Tchobanoglous, F. L. Burton, and H. D. Stensel, “Wastewater engineering: Treatment, disposal and reuse,” (International Ed.), Mc Graw Hill Press, 2003.
G. Mininni, A. R. Blanch, F. Lucena, and S. Berselli, “EU policy on sewage sludge utilization and perspectives on new approaches of sludge management,” Environmental Science and Pollution Research, Vol. 22, pp. 7361–7374, 2015. [CrossRef]
B. Wu, X. Dai, and X. Chai, “Critical review on dewatering of sewage sludge: Influential mechanism, conditioning technologies and implications to sludge re-utilizations,” Water Research, Vol. 180, Article 115912, 2020. [CrossRef]
İ. Öztürk, “Anaerobik arıtma ve uygulamaları,” Su Vakfı Yayınları, 2007. [Turkish]
M. Kim, Y. H. Ahn, and R. E. Speece, “Comparative process stability and efficiency of anaerobic digestion; mesophilic vs. thermophilic,” Water Research, Vol. 36, pp. 4369–4385, 2002. [CrossRef]
American Public Health Association, “Standard methods for the examination of water and wastewater,” (21st ed.), American Public Health Association (APHA), American Water Works Association (AWWA) and Water Environment Federation (WEF), 2005.
D. Erdirencelebi, and M. Kucukhemek, “Diagnosis of the anaerobic reject water effects on WWTP operational characteristics as a precursor of bulking and foaming,” Water Science and Technology, Vol. 71(4), pp. 572579, 2015. [CrossRef]
P. Winter, and P. Pearce, “Parallel digestion of secondary and primary sludge,” in Proceedings of the 15th European Biosolids and Organic Resources Conference, November, Aqua Enviro, Leeds, UK, 2010.
C. M. Braguglia, A. Gianico, A. Gallipoli, and G. Mininni, “The impact of sludge pre-treatments on mesophilic and thermophilic anaerobic digestion efficiency: Role of the organic load,” Chemical Engineering Journal, Vol. 270, pp. 362–371, 2015. [CrossRef]
N. Pinto, A. Carvalho, J. Pacheco, and E. Duarte, “Study of different ratios of primary and waste activated sludges to enhance the methane yield,” Water and Environment Journal, Vol. 30, pp. 203–210, 2016. [CrossRef]
L. Appels, J. Baeyens, J. Degreve, and R. Dewil, “Principles and potential of the anaerobic digestion of waste-activated sludge,” Progress in Energy Combustion Science, Vol. 34, pp. 755–781, 2008. [CrossRef]
D. Erdirençelebi, and C. Bayhan, “Feasibility and potential of separate anaerobic digestion of municipal sewage sludge fractions,” Water SA, Vol. 46(1), pp.123130, 2020. [CrossRef]
D. Erdirençelebi, and G. M. Ebrahimi, “Enhanced sewage sludge treatment via parallel anaerobic digestion at the upper mesophilic level,” Journal of Environmental Management, Vol. 320, Article 115850, 2022. [CrossRef]
C. F. Forster, “Bound water in sewage sludges and its relationship to sludge surfaces and sludge viscosities,” Journal of Chemical Technology & Biotechnology, Vol. 33B(1), pp. 76–84, 1983. [CrossRef]
J. Wingender, K. E. Jäger, and H.-C. Flemming, Interaction between extracellular polysaccharides and enzymes, In: J. Wingender, T. R. Neu (Eds.), “Microbial Extracellular Polymeric Substances,” pp. (1–19). Springer, 1999. [CrossRef]
H.-C. Flemming, and J. Wingender, “Relevance of microbial extracellular polymeric substances (EPSs). Part I. Structural and ecological aspects,” Water Science & Technology, Vol. 43 (6), pp. 1–8, 2001. [CrossRef]
J. Schmitt, U. P. Fringeli, and H.-C. Flemming, “Structural and temporal behaviour of biofilms investigated by FTIR-ATR spectroscopy,” in Proc. 11th Conference on Fourier Transform Spectroscopy, American Institute Physics Press, 1997. [CrossRef]
A. C. Chao, and T. M. Keinath, “Influence of process loading intensity on sludge clarification and thickening characteristics,” Water Research, Vol. 13(12), pp. 12121220, 1979. [CrossRef]
E. Neyens, J. Baeyens, R. Dewil, and B. De Heyder, “Advanced sludge treatment affects extracellular polymeric substances to improve activated sludge dewatering,” Journal of Hazardous Materials, Vol. 106B, pp. 83–92, 2004. [CrossRef]