An alternative method for removing nitrogen
The anaerobic digestion of sludge from wastewater treatment plants is currently seeing high demand as it reduces the organic fraction of sludge and enables the biogas to be recovered in the form of renewable energy. The dewatering liquor of the digested sludge, however, has a very high ammonia content and comprises between 15 to 35% of the nitrogen to be treated in the water line.
To comply with the discharge standards imposed by water directives, a new effluent treatment technique, which uses the nitrate-shunt method, has been jointly developed by the research teams of CERDEG and CIRSEE. By stopping nitrification at the nitrite stage, this alternative process, which uses the Degrémont Cyclor® SBR reactor, eliminates the nitrogen and achieves savings of approximately 25% on aeration energy, 40% on the addition of assimilable carbon and 30% on the quantity of sludge produced. The patented nitrate-shunt process significantly improves the overall operation of the installation and contributes to the near 40% reduction of its environmental impact.
Applications :
To date, this process of removing the nitrogen from high nitrogen content effluents using the nitrate-shunt method is being used at the Bilten wastewater treatment plant (Switzerland) and an industrial prototype is operational at the Creil plant (France), operated by Lyonnaise des Eaux. Other installations of the Group will benefit from this process in the months to come.
