title: Optimisation of sewage sludge anaerobic digestion through co-digestion with OFMSW: Effect of collection system and particle size.
abstract: The effect of organic fraction of municipal solid waste (OFMSW) loading rate and particulate size on the sewage sludge (SS) mesophilic anaerobic co-digestion was assessed in continuous stirred tank reactor at hydraulic retention time of 20days. The SS-OFMSW mixture composed by 54% of the volatile solids fed (inlet-VS), at OLR of 3.1kgCODm(-3)d(-1) (1.9kgVSm(-3)d(-1)), showed the highest increment on the volumetric methane production and yield of +200% and +59% respectively, under stable conditions. The effect of particulate size was assessed with the same mixture and same operational conditions but reducing the OFMSW particulate size from 20mm to 8mm with the aim to improve the hydrolysis step, but the results showed any influence in the OFMSW particulate size range analysed. In addition, specific biomass activity was assessed at the end of each co-digestion period. Results showed that OFMSW promoted β-oxidation syntrophic acetogens and the acetoclastic methanogens activity; although the last increase of the OFMSW percentage (from 47% to 54% inlet-VS) affected negatively the specific substrate activity, but not inhibitory effect was observed. Therefore, the results obtained in the continuous experiment could be related with some inhibitory or toxic effect and not due to hydrolysis limitation. The specific biomass activity test was demonstrated to be an interesting tool to evaluate and control the co-digestion process, especially when conventional parameters did not explain the behaviour of the biological system.
authors.affiliation: IRTA, GIRO Joint Research Unit IRTA-UPC, Torre Marimon, Barcelona, Spain; Ainia, Departamento de Medio Ambiente, Bioenergía e Higiene Industrial, Paterna, Valencia, Spain.
authors.forename: Gracia
authors.initials: G
authors.lastname: Silvestre
authors.affiliation: IRTA, GIRO Joint Research Unit IRTA-UPC, Torre Marimon, Barcelona, Spain.
authors.forename: August
authors.initials: A
authors.lastname: Bonmatí
authors.affiliation: IRTA, GIRO Joint Research Unit IRTA-UPC, Torre Marimon, Barcelona, Spain. Electronic address: belen.fernandez@irta.cat.
authors.forename: Belén
authors.initials: B
authors.lastname: Fernández
mesh_terms: D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D018533:Biomass; D019149:Bioreactors; D006868:Hydrolysis; D008697:Methane / Q000737:chemistry*; D009930:Organic Chemicals / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D010316:Particle Size; D012037:Refuse Disposal / Q000379:methods; D012722:Sewage; D062611:Solid Waste / Q000032:analysis*
chemical_list: D009930:Organic Chemicals; D012722:Sewage; D062611:Solid Waste; D008697:Methane; D010100:Oxygen
keywords: Anaerobic digestion; Co-digestion; OFMSW; Particle size; Sewage sludge