Nitrogen recovery from sludge centrate by membrane contactor: Influence of operating parameters and cleaning conditions

• Published in: Journal of environmental management Vol. 341; p. 118051
• Main Authors: Cifuentes-Cabezas, Magdalena, Luján-Facundo, María-José, Cuartas-Uribe, Beatriz, Iborra-Clar, Alicia, Mendoza-Roca, José-Antonio
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.09.2023
• Subjects: Ammonia; Ammonium Compounds; Ammonium recovery; Liquid-liquid membrane contactor; Nitrogen; Sewage - chemistry; Sludge centrate; Wastewater; Ammonium recovery; Liquid-liquid membrane contactor; Sludge centrate
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2023.118051

In urban wastewater treatment, the sludge generated is treated by anaerobic digestion, to be subsequently dehydrated by centrifuges. Currently, the liquid fraction obtained in this dehydration process is recirculated at the head of the treatment plant. However, its high nitrogen and phosphorus content makes it an effluent with high added value. The recovery of these nutrients could be an excellent alternative for the production of fertilizers or other industrial applications. In this study, the use of a liquid-liquid phase membrane contactor is presented as a favorable solution for the recovery of ammoniacal nitrogen from sludge centrated. The polypropylene hollow fiber membrane was evaluated considering its ammonia removal and recovery capacity. For this, different parameters were evaluated: the influence of the type and concentration of the acid solution, the wastewater pH, the flow rates of feeding and the acid stripping solution, and the contact time. Results showed that with a contact time of 65 min, ammonia removal and recovery percentages of the order of 90% were achieved. The flow rates of the stripping and feed solutions together with the acid concentration did not have a significant influence on the removal but on the recovery. Concerning used acid, sulphuric and phosphoric acid solutions achieved better results than nitric acid solution. The most critical parameter was the pH, obtaining the highest removal and recovery of ammonium at the highest pH. Finally, a stable cleaning protocol was obtained, between preventive and moderate cleanings to avoid severe cleanings, keeping the membrane at its maximum capacity. •Recovery of ammonium from sludge centrate with liquid-liquid membrane contactor.•Approximately 90% removal and recovery were achieved with a contact time of 65 min.•H2SO4 and H3PO4 were better extraction solution than HNO3, and pH was the most critical parameter.•Preventive and moderate cleanings manage to keep the membrane at its maximum capacity.