title: Synergistic co-digestion of solid-organic-waste and municipal-sewage-sludge: 1 plus 1 equals more than 2 in terms of biogas production and solids reduction.
abstract: Making good use of existing water infrastructure by adding organic wastes to anaerobic digesters improves the energy balance of a wastewater treatment plant (WWTP) substantially. This paper explores co-digestion load limits targeting a good trade-off for boosting methane production, and limiting process-drawbacks on nitrogen-return loads, cake-production, solids-viscosity and polymer demand. Bio-methane potential tests using whey as a model co-substrate showed diversification and intensification of the anaerobic digestion process resulting in a synergistical enhancement in sewage sludge methanization. Full-scale case-studies demonstrate organic co-substrate addition of up to 94% of the organic sludge load resulted in tripling of the biogas production. At organic co-substrate addition of up to 25% no significant increase in cake production and only a minor increase in ammonia release of ca. 20% have been observed. Similar impacts were measured at a high-solids digester pilot with up-stream thermal hydrolyses where the organic loading rate was increased by 25% using co-substrate. Dynamic simulations were used to validate the synergistic impact of co-substrate addition on sludge methanization, and an increase in hydrolysis rate from 1.5 d(-1) to 2.5 d(-1) was identified for simulating measured gas production rate. This study demonstrates co-digestion for maximizing synergy as a step towards energy efficiency and ultimately towards carbon neutrality.
authors.affiliation: University of Innsbruck, 6020 Innsbruck, Austria; alpS - Centre for Climate Change Adaptation, 6020 Innsbruck, Austria.
authors.forename: Peter
authors.initials: P
authors.lastname: Aichinger
authors.affiliation: Dynamita SARL, Nyons, France; DC WATER, 5000 Overlook Ave., SW Washington, DC 20032, USA.
authors.forename: Tanush
authors.initials: T
authors.lastname: Wadhawan
authors.affiliation: University of Innsbruck, 6020 Innsbruck, Austria; alpS - Centre for Climate Change Adaptation, 6020 Innsbruck, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Kuprian
authors.affiliation: Bucknell University, Lewisburg, PA 17837, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Higgins
authors.affiliation: alpS - Centre for Climate Change Adaptation, 6020 Innsbruck, Austria; Abwasserverband Zirl u.U., 6170 Zirl, Austria.
authors.forename: Christian
authors.initials: C
authors.lastname: Ebner
authors.affiliation: Abwasserverband AIZ, 6261 Strass i. Z, Austria.
authors.forename: Christian
authors.initials: C
authors.lastname: Fimml
authors.affiliation: DC WATER, 5000 Overlook Ave., SW Washington, DC 20032, USA.
authors.forename: Sudhir
authors.initials: S
authors.lastname: Murthy
authors.affiliation: ARAconsult GmbH, 6020 Innsbruck, Austria. Electronic address: wett@araconsult.at.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Wett
mesh_terms: D000641:Ammonia / Q000032:analysis; D056804:Biofuels / Q000032:analysis*; D008697:Methane / Q000032:analysis*; D012037:Refuse Disposal / Q000379:methods*; D012722:Sewage / Q000032:analysis*; D062611:Solid Waste / Q000032:analysis*; D014865:Waste Disposal, Fluid / Q000379:methods*; D018505:Waste Management
chemical_list: D056804:Biofuels; D012722:Sewage; D062611:Solid Waste; D000641:Ammonia; D008697:Methane
keywords: Co-substrate; Methane yield; Sludge reduction; Wastewater; Whey