title: Anaerobic co-digestion of sewage sludge and strawberry extrudate under mesophilic conditions.
abstract: The biomethanization of sewage sludge has several disadvantages such as low methane yield, poor biodegradability and nutrient imbalance. In this paper, a sewage sludge and strawberry extrudate mixture in a proportion of 40:60 (wet weight) is proposed to improve the viability of the process. The addition of an easily biodegradable co-substrate enhanced the nutrient balance and diluted the heavy metals and inhibitors from sewage sludge. Two different experimental set-ups at lab and semi-pilot scale were employed in order to ensure the reproducibility and significance of the obtained values. Co-digestion improved the stability of the process by decreasing the alkalinity to a mean value of 3215 ± 190 mg CaCO₃/L, while maintaining the pH within the optimal range for anaerobic digestion. The methane yield coefficient and biodegradability were 176 L/kg VS (total volatile solids) (0°C, 1 atm) and 81% (VS), respectively. Kinetic parameters decreased at the highest loads, suggesting the occurrence of a slowing down phenomenon. A quality organic amendment with a heavy metal content lower than the limits established under European legislation for agricultural applications was obtained from the digestate of the proposed treatment.
authors.affiliation: a Department of Inorganic Chemistry and Chemical Engineering , University of Cordoba , Cordoba , Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Serrano
authors.forename: José A
authors.initials: JA
authors.lastname: Siles
authors.forename: Arturo F
authors.initials: AF
authors.lastname: Chica
authors.forename: M Ángeles
authors.initials: MÁ
authors.lastname: Martín
mesh_terms: D000383:Agriculture; D000693:Anaerobiosis; D019149:Bioreactors; D005308:Fertilizers; D031985:Fragaria; D008697:Methane / Q000378:metabolism; D012722:Sewage; D014865:Waste Disposal, Fluid / Q000379:methods; D014866:Waste Products
chemical_list: D005308:Fertilizers; D012722:Sewage; D014866:Waste Products; D008697:Methane
keywords: digestate; mesophilic anaerobic co-digestion; sewage sludge; strawberry extrudate; volatile fatty acids