Autohydrolysis pretreatment of secondary sludge for anaerobic digestion |
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Affiliation: | 1. Advanced Environmental Biotechnology Centre, Nanyang Environment and Water Research Institute, Nanyang Technological University, Singapore 637141, Singapore;2. Nanyang Environment and Water Research Institute, Nanyang Technological University, Singapore 637141, Singapore;3. School of Civil and Environmental Engineering, Nanyang Technological University, Singapore 639798, Singapore;4. Public Utilities Board, Water Reclamation (Plants) Department, Singapore 628507, Singapore;1. University of Science, Vietnam National University, Ho Chi Minh City, Viet Nam;2. Université de Toulouse, Laboratoire de Génie Chimique, INP-ENSIACET, France |
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Abstract: | The increase in the number of wastewater treatment plants and the quality required for the residue produced makes it necessary to improve the efficiency of anaerobic digestion of sludge. Pretreatments of secondary sludge have shown important advantages in the elimination of volatile solids and pathogenic microorganisms from the sludge, and they have also had a positive effect on biogas production. However, such methods are associated with high operating costs. This paper shows the behavior of a autohydrolysis pretreatment, which consists of subjecting the secondary sludge to a temperature of 55 °C for 12–24 h with a limited amount of oxygen under batch operation. The pretreatment results in a high solubilization of organic matter, increasing the fluidity of the sludge and improving the biogas production. This study focuses on the evaluation of the influence of oxygen and the initial sludge concentration on the pretreatment behavior. The main results obtained showed that when autohydrolysis pretreatment was carried out for 12 h, with a high solid concentration and microaerobic conditions, the solubilization of organic matter was increased by 40%, the methane productivity was improved by 23%, and there was an overall improvement in sludge fluidity. Moreover, the energy assessment of the autohydrolysis pretreatment and anaerobic digestion system showed the energetic feasibility of this treatment method, since the increase in energy production compensates for the extra energy required to carry out the pretreatment. |
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Keywords: | Anaerobic processes Biogas Enzymes Improvement Rheology Sludge pretreatment |
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