Inhibition on anammox bacteria upon exposure to digestates from biogas plants treating the organic fraction of municipal solid waste and the role of conductivity

The aim of this research was to evaluate the applicability of the anammox process for removing nitrogen from the supernatant originating from the anaerobic digestion of the organic fraction of municipal solid waste (OFMSW). The short term inhibitory potential of this concentrated wastewater was evaluated by means of batch tests in terms of maximum specific anammox activity reduction. A total of 20 real wastewater samples were tested originating from 4 different full scale anaerobic digestion plants treating OFMSW. Activity reduction between 73% and 89% was observed in the presence of undiluted real wastewaters. The specific activity remained stable for 6–7 days after the initial reduction, thus suggesting its treatability even without dilution. The inhibitory effect of both the real and synthetic saline media tested could be modelled as a function of conductivity. IC50 of 6.1 mS/cm was obtained for exposure to the tested liquid fraction of biowaste digestate.