Speaker
Description
Many WWTPs utilize anaerobic digestion (AD) for primary sludge and secondary sludge because of their efficiency in reducing sludge and recovering energy from it. It is challenging to liberate biodegradable carbohydrates and organic compounds from secondary sludge due to the presence of sludge cells and extracellular polymeric substances (EPS) (Bougrier et al., 2005). A lower biodegradability than primary sludge makes secondary sludge more difficult to employ in AD, which makes it less suitable for this use (Mottet et al., 2010). This has a considerable negative influence on the efficacy of sludge reduction in addition to energy recovery from secondary sludge in AD systems.
The disintegration of sludge particles is a popular method for increasing the biodegradability of secondary sludge components. Alkaline pretreatment is commonly coupled with thermal treatment because the combined treatment can minimize the amount of alkali and energy required (Shehu et al., 2012). A co-operative impact of thermal-alkaline pretreatment on sludge degradability has been documented in several investigations (Kim et al., 2003; Valo et al., 2004). In this investigation, the biodegradability enhancement of secondary sludge with alkaline-thermal pretreatment was investigated with the BMP test. The use of alkaline-thermal pretreatment resulted in successful degradation of secondary sludge and increased CH4 generation from the waste. Amid the different temperatures (60–140 degrees Celsius) and pH values (6.9–12), a modest temperature of 60 degrees Celsius and a pH of 10 produced the greatest economic gain while also producing the most CH4. The highest CH4 yield of 215.6 mL/g COD was attained by using secondary sludge which is pretreated at 60 °C and pH 10 for 24 h. Furthermore, a maximum solubilization rate of 58.7% was achieved after alkaline-thermal pretreatment. And LB-EPS of pretreated sludge was significantly increased compared to untreated sludge. Alkaline-thermal pretreatment increased both SCOD and LB-EPS by sludge disintegration.
Therefore, the mild alkaline-thermal pretreatment of sludge would be beneficial in terms of improving the digesting performance and economic benefit of the process.
References
Bougrier, C., Carrère, H., Delgenes, J. P. (2005), Solubilisation of waste-activated sludge by ultrasonic treatment. Chem. Eng. J., 106(2), 163-169.
Cayetano, R. D. A., Oliwit, A. T., Kumar, G., Kim, J. S., Kim, S. H. (2019), Optimization of soaking in aqueous ammonia pretreatment for anaerobic digestion of African maize bran. Fuel., 253, 552-560.
Kim, J., Park, C., Kim, T.H., Lee, M., Kim, S., Kim, S.W., Lee, J. (2003), Effects of various pretreatments for enhanced anaerobic digestion with waste activated sludge. J. Biosci. Bioeng., 95, 271–275.
Mottet, A., François, E., Latrille, E., Steyer, J. P., Déléris, S., Vedrenne, F., Carrère, H. (2010), Estimating anaerobic biodegradability indicators for waste activated sludge. Chem. Eng. J., 160(2), 488-496.
Shehu, M.S., Abdul Manan, Z., Wan Alwi, S.R. (2012), Optimization of thermo-alkaline disintegration of sewage sludge for enhanced biogas yield. Bioresour. Technol., 114, 69–74.
Valo, A., Carrere, H., Delgenes, J.P. (2004), Thermal, chemical and thermo-chemical pre-treatment of waste activated sludge for anaerobic digestion. J. Chem. Technol. Biotechnol., 79, 1197–1203.
| Keywords | Anaerobic digestion, Biogas, Pretreatment |
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