title: Improving biogas production from continuous co-digestion of oily wastewater and waste-activated sludge by hydrodynamic cavitation pre-treatment.
abstract: Hydrodynamic cavitation (HC) was evaluated as a pretreatment for synthetic oily wastewater (OWW) to be co-digested with waste-activated sludge (WAS). The main objective of the present research was the enhancement of biogas production by the application of HC pretreatment. HC was applied to the OWW, and the OWW and WAS were added to a 50 L continuous digestion reactor. As a control system, an identical digestion reactor was set up for co-digestion of the WAS and the OWW without pretreatment. The reactors were initially filled with inoculum and the hydraulic retention time (HRT) was set to 22 d. The HRT was gradually reduced to 19, 16, and finally 13 d, but the substrate quality was kept constant. The loading rate, accordingly, increased from 0.86 to 1.46 g TVS/(L d). The biogas volume was recorded online and its quality was analyzed regularly. The HC improved biogas production up to 43% at 22 d of HRT. Reducing the HRT decreased biogas production from the main reactor while that of the control reactor was more or less constant. HC also increased the biogas methane content; the methane concentration of the main reactor was about 3% higher than the methane concentration of the control reactor. The main reactor experienced no clogging or accumulation of fatty materials.
authors.affiliation: a Faculty of Environment , University of Tehran , Tehran , Iran.|b Faculty of Civil and Environmental Engineering , Ostfalia University of Applied Sciences , Suderburg , Germany.
authors.forename: Nima
authors.identifier: http://orcid.org/0000-0002-4670-5677
authors.initials: N
authors.lastname: Habashi
authors.affiliation: c Faculty of Civil, Water and Environmental Engineering , Shahid Beheshti University , Tehran , Iran.
authors.forename: Abolghasem
authors.identifier: http://orcid.org/0000-0001-7913-5239
authors.initials: A
authors.lastname: Alighardashi
authors.affiliation: b Faculty of Civil and Environmental Engineering , Ostfalia University of Applied Sciences , Suderburg , Germany.
authors.forename: Artur
authors.identifier: http://orcid.org/0000-0002-2495-1770
authors.initials: A
authors.lastname: Mennerich
authors.affiliation: a Faculty of Environment , University of Tehran , Tehran , Iran.
authors.forename: Nasser
authors.initials: N
authors.lastname: Mehrdadi
authors.affiliation: a Faculty of Environment , University of Tehran , Tehran , Iran.
authors.forename: Ali
authors.initials: A
authors.lastname: Torabian
mesh_terms: D000693:Anaerobiosis; D056804:Biofuels; D019149:Bioreactors; D057446:Hydrodynamics; D008697:Methane / Q000032:analysis*; D012722:Sewage; D062065:Wastewater
chemical_list: D056804:Biofuels; D008697:Methane; D012722:Sewage; D062065:Wastewater
keywords: Co-digestion; biogas increase; emulsifying; hydrodynamic cavitation; oily wastewater; waste-activated sludge