title: Evaluation of the improvement of sonication pre-treatment in the anaerobic digestion of sewage sludge.
abstract: Sewage sludge is a polluting and hazardous waste generated in wastewater treatment plants with severe management problems. The high content in heavy metal, pathogens and micropolluting compounds limit the implementation of the available management methods. Anaerobic digestion could be an interesting treatment method, but must be improved since the biomethanisation of sewage sludge entails low biodegradability and low methane production. A sonication pre-treatment at lab scale is proposed to increase the organic matter solubilisation of sewage sludge and enhance the biomethanisation yield. Sonication time was optimised by analysing the physicochemical characteristics of sewage sludge (both total and soluble fraction) at different pre-treatment times. The pre-treatment time was fixed at 45 min under the study conditions given that the solubilisation of organic matter did not increase significantly at lower sonication times, whereas the concentration of total nitrogen increased markedly at higher times. The volatile fatty acids generation rate was also evaluated for the pre-treatment conditions. The anaerobic digestion of untreated and pre-treated sewage sludge was subsequently compared and promising results were obtained for loads of 1.0 g VS/L (VS, total volatile solids). The methane yield coefficient increased from 88 to 172 mLSTP/g VS (STP, 0 °C, 1 atm) after the pre-treatment, while biodegradability was found to be around 81% (in VS). Moreover, the allowed organic loading rate and methane production rate observed for the sewage sludge reached values of up to 4.1 kg VS/m(3)·d and 1270 LSTP/m(3)·d, respectively.
authors.affiliation: 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. Electronic address: iq2masam@uco.es.
authors.forename: María Ángeles
authors.initials: MÁ
authors.lastname: Martín
authors.affiliation: 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.
authors.forename: Inmaculada
authors.initials: I
authors.lastname: González
authors.affiliation: 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.
authors.forename: Antonio
authors.initials: A
authors.lastname: Serrano
authors.affiliation: 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.
authors.forename: José Ángel
authors.initials: JÁ
authors.lastname: Siles
mesh_terms: D001421:Bacteria, Anaerobic / Q000378:metabolism*; D001673:Biodegradation, Environmental; D019149:Bioreactors; D002244:Carbon / Q000032:analysis; D005232:Fatty Acids, Volatile / Q000378:metabolism; D008697:Methane / Q000096:biosynthesis*; D009584:Nitrogen / Q000032:analysis; D012722:Sewage / Q000382:microbiology*; D013010:Sonication / Q000379:methods*
chemical_list: D005232:Fatty Acids, Volatile; D012722:Sewage; D002244:Carbon; D009584:Nitrogen; D008697:Methane
keywords: Mesophilic anaerobic digestion; Methane; Optimisation; Pre-treatment time; Sewage sludge; Sonication pre-treatment