Microbial electrolysis cells for return flow: Simultaneous nitrogen and carbon removal

• Published in: Journal of environmental management 2021-07, Vol.289, p.112499-112499, Article 112499
• Main Authors: San-Martín, María Isabel, Pelaz, Guillermo, Escapa, Adrián, Morán, Antonio
• Format: Article
• Language: English
• Subjects: Bioreactors; Carbon; Electrolysis; Nitrogen; Sewage; Waste Disposal, Fluid; Waste Water; Water Purification
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2021.112499

The concentration of solids in secondary sludge before anaerobic digestion in a wastewater treatment plant, bring about the production of a return flow, which contains high concentrations of all the common pollutant parameters. This return flow could unfavourably affect the performance of the processes and effluent quality of the waterline. Here, we report the utilisation of three similar microbial electrolysis cells reactors that performs simultaneous carbon and nitrogen removal to reduce the impact of the return flow in the plant. The result of the batch-fed (72 h) experiment showed COD and total nitrogen removal efficiencies that reached 90% and 80%, respectively, supporting the premise that return flows are suitable substrates for a bioelectrochemical treatment. The three reactors followed similar trends, showing good replicability and confirming the potential of MECs as a feasible technology for return flow treatment. Furthermore, when cathodic conversion efficiency was higher than 80%, the pure hydrogen production allows to recover the electric energy consumption, indicating that the system could be theoretically energy neutral. •90% of COD and 80% of TN could be effectively removal.•Organic matter in return flow was easily degradable substrate for exoelectrogens.•A purity of H2 of more than 97% was obtained in the cathode.•Cathodic conversion efficiency >80% would provide energy self-sufficiency.