Unravelling the active microbial community in a thermophilic anaerobic digester-microbial electrolysis cell coupled system under different conditions

Thermophilic anaerobic digestion (AD) of pig slurry coupled to a microbial electrolysis cell (MEC) with a recirculation loop was studied at lab-scale as a strategy to increase AD stability when submitted to organic and nitrogen overloads. The system performance was studied, with the recirculation loop both connected and disconnected, in terms of AD methane production, chemical oxygen demand removal (COD) and volatile fatty acid (VFA) concentrations. Furthermore, the microbial population was quantitatively and qualitatively assessed through DNA and RNA-based qPCR and high throughput sequencing (MiSeq), respectively to identify the RNA-based active microbial populations from the total DNA-based microbial community composition both in the AD and MEC reactors under different operational conditions. Suppression of the recirculation loop reduced the AD COD removal efficiency (from 40% to 22%) and the methane production (from 0.32 to 0.03 m3m-3d-1). Restoring the recirculation loop led to a methane production of 0.55 m3m-3d-1concomitant with maximum MEC COD and ammonium removal efficiencies of 29% and 34%, respectively. Regarding microbial analysis, the composition of the AD and MEC anode populations differed from really active microorganisms. Desulfuromonadaceae was revealed as the most active family in the MEC (18%–19% of the RNA relative abundance), while hydrogenotrophic methanogens (Methanobacteriaceae) dominated the AD biomass.Postprint (author's final draft

Pig slurry concentration by vacuum evaporation: influence of previous mesophilic anaerobic digestion process

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Overcoming organic and nitrogen overload in thermophilic anaerobic digestion of pig slurry by coupling a microbial electrolysis cell

The combination of the anaerobic digestion (AD) process with a microbial electrolysis cell (MEC) coupled to an ammonia stripping unit as a post-treatment was assessed both in series operation, to improve the quality of the effluent, and in loop configuration recirculating the effluent, to increase the AD robustness. The MEC allowed maintaining the chemical oxygen demand removal of the whole system of 46 ± 5% despite the AD destabilization after doubling the organic and nitrogen loads, while recovering 40 ± 3% of ammonia. The AD-MEC system, in loop configuration, helped to recover the AD (55% increase in methane productivity) and attained a more stable and robust operation. The microbial population assessment revealed an enhancement of AD methanogenic archaea numbers and a shift in eubacterial population. The AD-MEC combined system is a promising strategy for stabilizing AD against organic and nitrogen overloads, while improving the quality of the effluent and recovering nutrients for their reutilization.Postprint (author's final draft

Ammonia air stripping from pig slurry: influence of previous mesophilic anaerobic digestion process

The solution to environmental problems associated with livestock wastes requires a broad integrated approachPostprint (published version

Future trends on manure processing activities in Europe

Technical Report No. V concerning “Manure Processing Activities in Europe” to the European Commission, Directorate-General Environment. Project reference: ENV.B.1/ETU/2010/0007. Publicat el 29.03.2012 a: http://ec.europa.eu/environment/water/water-nitrates/studies.htmlPreprin

Nitrogen removal in a two-chambered microbial fuel cell: Establishment of a nitrifying-denitrifying microbial community on an intermittent aerated cathode

A microbial fuel cell (MFC) was used to study nitrogen dynamics and its feasibility for high strength wastewater treatment. Intermittent aeration was applied on the cathode chamber accomplishing the establishment of a simultaneous nitrifying-denitrifying microbial community. A total of 30.4% of the N-NH4 + migrated through the ion exchange membrane being primarily nitrified at the cathode chamber. When intermittent aeration was applied in the cathode, denitrification also occurred achieving 17.8% of nitrate removal without acetate addition, and 41.2% with acetate addition. The microbial community analysis revealed that the nitrification process at the cathode chamber could be explained due to a high predominance of Nitrosomonas sp. as ammonia-oxidising bacteria and other Comamonadaceae phylotypes as potential denitrifiers. Parallel batch denitrification assays, carried out outside the MFC using the cathode effluent, confirmed the existence of heterotrophic denitrification processes with other well known denitrifying dominant phylotypes enrichment (Burkholderiadaceae, Comamonadaceae, Alcaligenaceae).Postprint (author's final draft

Técnicas de gestión de deyecciones en zonas de alta densidad ganadera

En los últimos años hemos pasado de hablar de “verter purines al campo” a “fertilizar con purines”. Este cambio de nomenclatura es indicativo de una evolución positiva en el sector, en la que además estamos aprendiendo que no debe abordarse la problemática de las deyecciones como algo independiente de la producción animal. La gestión de las deyecciones es una actividad que ha de formar parte íntegra de la producción ganadera, tan primaria como la alimentación o el control sanitario y estrechamente relacionada con estas. Actualmente el mercado ofrece a los ganaderos una gran cantidad de alternativas tecnológicas para el tratamiento de las deyecciones, pero sería un error considerar únicamente la tecnología como la solución a los problemas de contaminación ocasionados por las deyecciones. La solución es siempre una combinación de gestión y tecnología, en la que la elección de esta última ha de ser resultado de los estudios realizados para diseñar el plan de gestión de los nutrientes (PGN). En zonas de alta densidad ganadera, la gestión colectiva permite optimizar la logística de transporte y aplicación, así como la estrategia de procesado de deyecciones.Postprint (published version

Removal of volatile fatty acids and ammonia recovery from unstable anaerobic digesters with a microbial electrolysis cell

Continuous assays with a microbial electrolysis cell (MEC) fed with digested pig slurry were performed to evaluate its stability and robustness to malfunction periods of an anaerobic digestion (AD) reactor and its feasibility as a strategy to recover ammonia. When performing punctual pulses of volatile fatty acids (VFA) in the anode compartment of the MEC, simulating a malfunction of the AD process, an increase in the current density was produced (up to 14 times, reaching values of 3500 mA m-2) as a result of the added chemical oxygen demand (COD), especially when acetate was used. Furthermore, ammonium diffusion from the anode to the cathode compartment was enhanced and the removal efficiency achieved up to 60% during daily basis VFA pulses. An AD-MEC combined system has proven to be a robust and stable configuration to obtain a high quality effluent, with a lower organic and ammonium contentPeer ReviewedPostprint (published version

Improving anaerobic digestion stability, effluent quality and ammonia recovering with a microbial electrolysis cell integrated system

Anaerobic digestion (AD) is nowadays widely used for processing various kinds of wastes, as livestock manure. Despite it is considered as a robust process, when it is performed at thermophilic range, beside a number of advantages, it is more sensitive to inhibition due to diverse substances that may be present in the waste stream, as ammonia. Furthermore, the AD process does not modify the total content of N of the digestates. So, it is interesting to find new technologies that can help to maintain effluent quality within the desired limits, while recovering nutrients from the digestates.This research was funded by the Spanish Ministry of Economy and Competitiveness (INIA project RTA2012- 00096-00-00). Also financial support was received by the Catalan Government (pre-doctoral fellowship 2013FI_B 00014).Postprint (published version

Manure treatment technologies: on-farm versus centralized strategies. NE Spain case study

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