Comparison of Pre-treatment Technologies to Improve Sewage Sludge Biomethanization
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Comparison of Pre-treatment Technologies to Improve Sewage Sludge Biomethanization Antonio Serrano 1 & José Ángel Siles 1 & María del Carmen Gutiérrez 1 & María de los Ángeles Martín 1 Received: 6 October 2020 / Accepted: 8 November 2020/ # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
This research study evaluates various pre-treatments to improve sewage sludge solubilization prior to treatment by mesophilic anaerobic digestion. Microwave, thermal, and sonication pre-treatments were compared as these pre-treatments are the most commonly used for this purpose. The solubilization of sewage sludge was evaluated through the variation in soluble total organic carbon (sTOC, mg/L) and soluble total nitrogen (sTN, mg/L). Thermal and microwave pre-treatments increased sTOC/VS by 19.2% and 83.4% (VS, total volatile solids), respectively, after applying lower specific energy through (20 kJ/g TS, approximately) (TS, total solids) unlike the sonication pre-treatment, which required 136 kJ/g TS. Although sTN content did not increase significantly with the pre-treatments with respect to sTOC, both showed proportional trends. Sonication pretreatments allowed the highest increase in volatile fatty acids (VFA) with respect to the raw sewage sludge (15% ΔVFA/sTOC). Methane production with and without pre-treatment was also evaluated. Methane production increased by 95% after applying sonication pretreatment compared to the methane production of raw sewage sludge. Thermal and microwave pre-treatments entailed lower improvements (29% and 20%, respectively). Economically, thermal pre-treatments were the most viable alternative at real scale. Keywords Mesophilic anaerobic digestion . Sewage sludge . Sonication . Microwave . Thermal pre-treatment
Introduction The management, processing, and disposal of urban wastewater treatment plant (WWTP) sewage sludge has been and continues to be one of the greatest challenges of the wastewater
* María de los Ángeles Martín [email protected]
1
Department of Inorganic Chemistry and Chemical Engineering, University of Cordoba, Campus Universitario de Rabanales, Edificio Marie Curie (C-3), Ctra. N IV, km 396, 14071 Cordoba, Spain
Applied Biochemistry and Biotechnology
sector [1]. Sewage sludge is difficult to manage due to the huge volume produced and the presence of undesirable compounds such as heavy metals, organic micropollutants, and pathogens [2]. These undesirable compounds could entail high environmental impacts and limit the available methods for sewage sludge management [3]. Anaerobic digestion is a treatment technology that is being developed worldwide to treat this polluting and hazardous waste [4]. This technology has several advantages such as the reduction of mass and pathogens, the removal of odors, and, more importantly, the recovery of energy as methane [5, 6]. However, the anaerobic digestion of sewage sludge should be improved as it usually entails low biodegradability and low methane production, which could limit its industrial implementation [7]
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