Two-phase (acidogenic-methanogenic) anaerobic fixed bed biofilm reactor enhances the biological domestic sewage treatment: Perspectives for recovering bioenergy and value-added by-products. (1st September 2022)

• Record Type: Journal Article
• Authors: Carneiro, Rodrigo B.; Gomes, Gisele M.; Zaiat, Marcelo; Santos-Neto, Álvaro J.
• Is Part Of: Journal of environmental management. Volume 317(2022)
• Publication Date: 2022-09-01
• Subjects: Anaerobic digestion -- Biomethane -- Fermentation -- Kinetics -- Methanoregula -- Volatile organic acids; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2022.115388
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: The organic matter bioconversion into methane during anaerobic digestion (AD) comprises different steps, the acidogenic and methanogenic phases being clearly distinct in terms of metabolic activities. In this work, new configurations of anaerobic fixed bed biofilm reactors (AFBBR) were operated under conventional methanogenic conditions (single phase – SP-AFBBR, M1 R), and in a sequential two-phase system, acidogenic reactor followed by methanogenic reactor (TP-AFBBR, AcR + M2 R), in order to verify the impact of the AD phase separation on the overall system performance in operational, kinetics and microbiological aspects. The results indicated that feeding the methanogenic reactor with the acidogenic effluent stream provided a shorter operating start-up period (11 and 32 days for SP and TP-AFBBR, respectively), a greater alkalinity generation (0.14 and 0.41 g-CaCO3 ·g-CODremoved −1 for M1 R and M2 R, respectively), and the optimization of biomethane production (methane yield of 95 and 154 N-mLCH4 ·g-CODremoved −1 for M1 R and M2 R, respectively). The COD removal kinetics was also favored in the TP-AFBBR (k1-COD = 1.4 and 2.9 h −1 for M1 R and M2 R, respectively), since the soluble fermentation products were readily bioavailable to the biomass in the reactor. Hydrogenotrophic methanogenesis was the predominant pathway in the M2 R, while the Methanosaeta -driven acetoclastic pathway predominated in the M1 R. The greater diversity of Bacteria and Archaea in M2 R denotes a better balance between the species that degrade volatile organic acids from AcR (i.e. Syntrophorhabdus, Syntrophus and Syntrophobacter ) and the hydrogenotrophic methanogens ( Methanoregula, Methanolinea and Methanospirillum ) that consume the biodegradation products. The estimated bioenergy generation potential (range of 0.39–0.64 kWh·m −3 -sewage considering the COD removed) for full-scale TP-sewage treatment plants evidences the feasibility of energetic recovery in the domestic sewage anaerobic treatment. Graphical abstract: Image 1 Highlights: Two-phase reactor enhances the biomethanation during sewage anaerobic digestion. Organic matter removal kinetics was favored in the two-phase anaerobic reactor. Acidogenic reactor shifts the methanogenic phase to the hydrogenotrophic pathway. Lactococcus and Clostridium are the key-players in the organic acids production. Phases separation makes it feasible the bioenergy recovery in the sewage treatment.