Biological Short-Cut Nitrogen Removal from Anaerobic Digestate in a Demonstration Sequencing Batch Reactor

The paper deals with a demonstration study where the nitrogen biological removal from anaerobic supernatants of sewage sludge and organic fraction of the municipal solid waste (OFMSW) was carried out by short-cut nitrification denitrification. The anaerobic supernatant was fed to the demonstration sequencing batch reactor (SBR) directly from the belt press of the full scale municipal WWTP. The SBR had reaction volume of 2.7 m(3) and was engineered on the basis of control algorithms designed by the authors. It was equipped with in-situ probes for the direct ((N-NH4, N-NOx) and indirect (DO, ORP, pH, conductivity) control of biological nitrogen removal. The SBR, inoculated with activated sludge coming from the Treviso municipal wastewater treatment plant (WWTP), treated up to 1.1 kgN/m(3) d and removed more than 90% of the influent total nitrogen, when the oxygen transfer efficiency was not drastically influenced by the liquor's salinity. In spite of the different operating and environmental conditions, the effluent showed stable N-NO2/N-NOx ratio higher than 0.9.