Comparison of the Effects of Continuous Flow Microwave Pre-treatment with Different Intensities on the Anaerobic Digestion of Sewage Sludge for Sustainable Energy Recovery from Sewage Treatment Plant

Authors: D. Hephzibah, P. Kumaran, N. M. Saifuddin

Abstract:

Anaerobic digestion is a well-known technique for sustainable energy recovery from sewage sludge. However, sewage sludge digestion is restricted due to certain factors. Pre-treatment methods have been established in various publications as a promising technique to improve the digestibility of the sewage sludge and to enhance the biogas generated which can be used for energy recovery. In this study, continuous flow microwave (MW) pre-treatment with different intensities were compared by using 5 L semi-continuous digesters at a hydraulic retention time of 27 days. We focused on the effects of MW at different intensities on the sludge solubilization, sludge digestibility, and biogas production of the untreated and MW pre-treated sludge. The MW pre-treatment demonstrated an increase in the ratio of soluble chemical oxygen demand to total chemical oxygen demand (sCOD/tCOD) and volatile fatty acid (VFA) concentration. Besides that, the total volatile solid (TVS) removal efficiency and tCOD removal efficiency also increased during the digestion of the MW pre-treated sewage sludge compared to the untreated sewage sludge. Furthermore, the biogas yield also subsequently increases due to the pre-treatment effect. A higher MW power level and irradiation time generally enhanced the biogas generation which has potential for sustainable energy recovery from sewage treatment plant. However, the net energy balance tabulation shows that the MW pre-treatment leads to negative net energy production.

Keywords: Anaerobic digestion, biogas, microwave pre-treatment, sewage sludge.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1110213

References:

[1] Yew, L. (2012) Energy and Resource Baseline Analysis of a Sewage Treatment Plant. Undergraduate. Universiti Tenaga Nasional.
[2] Montgomery, L. and Bochmann, G. (2014). Pretreatment of Feedstock for Enhanced Biogas Procution. Energy from Biogas. IEA Bioenergy.
[3] Appels, L., Baeyens, J., Degrève, J. and Dewil, R. (2008). Principles and Potential of the Anaerobic Digestion of Waste-activated Sludge. Progress in Energy and Combustion Science, 34 (6), pp. 755- 781.
[4] Carlsson, M., Lagerkvist, A. and Morgan-Sagastume, F. (2012). The Effects of Substrate Pre-treatment on Anaerobic Digestion Systems: A Review. Waste Management, 32(9), pp.1634-1650.
[5] Hephzibah, D., Kumaran, P. and Saifuddin, N. (2014). Pre-Treatment of Sewage Sludge to Enhance Biogas Production to Generate Green Energy for Reduction of Carbon Footprint in Sewage Treatment Plant (STP). In: Green Energy for Sustainable Development (ICUE), 2014 International Conference and Utility Exhibition. (online) Pattaya City: IEEE, pp.1-5. Available at: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6829007&isn umber=6828886 (Accessed 15 Jun. 2015).
[6] Bougrier, C., Delgenès, J. and Carrère, H. (2008). Effects of thermal treatments on five different waste activated sludge samples solubilisation, physical properties and anaerobic digestion. Chemical Engineering Journal, 139(2), pp.236-244.
[7] Eskicioglu, C., Kennedy, K. and Droste, R. (2006). Characterization of soluble organic matter of waste activated sludge before and after thermal pretreatment. Water Research, 40(20), pp.3725-3736.
[8] Tyagi, V. and Lo, S. (2013). Microwave irradiation: A sustainable way for sludge treatment and resource recovery. Renewable and Sustainable Energy Reviews, 18, pp.288-305.
[9] Appels, L., Houtmeyers, S., Degrève, J., Van Impe, J. and Dewil, R. (2013). Influence of microwave pre-treatment on sludge solubilization and pilot scale semi-continuous anaerobic digestion.Bioresource Technology, 128, pp.598-603.
[10] Beszédes, S., László, Z., Horváth, Z., Szabó, G. and Hodúr, C. (2011). Comparison of the effects of microwave irradiation with different intensities on the biodegradability of sludge from the dairy- and meatindustry. Bioresource Technology, 102(2), pp.814-821.
[11] Feng, X., Lei, H., Deng, J., Yu, Q. and Li, H. (2009). Physical and chemical characteristics of waste activated sludge treated ultrasonically. Chemical Engineering and Processing: Process Intensification, 48(1), pp.187-194.
[12] Eskicioglu, C., Kennedy, K. and Droste, R. (2007). Enhancement of Batch Waste Activated Sludge Digestion by Microwave Pretreatment. Water Environment Research, 79(11), pp.2304-2317.
[13] Park, W., Ahn, J., Hwang, S. and Lee, C. (2010). Effect of output power, target temperature, and solid concentration on the solubilization of waste activated sludge using microwave irradiation. Bioresource Technology, 101(1), pp.S13-S16.
[14] Yu, Q., Lei, H., Yu, G., Feng, X., Li, Z. and Wu, Z. (2009). Influence of microwave irradiation on sludge dewaterability. Chemical Engineering Journal, 155(1-2), pp.88-93.
[15] Park, W. and Ahn, J. (2011). Effects of microwave pretreatment on mesophilic anaerobic digestion for mixture of primary and secondary sludges compared with thermal pretretament. Environmental Engineering Research, 16(2), pp.103-109.
[16] Hosahalli, S. and Manguang, L. (2011). Influence of system variables on the heating characteristics of water during continuous flow microwave heating. International Journal of Microwave Science Technology, 2011.