Autotrophic nitrogen removal from digested agro-wastes

A lab-scale investigation has allowed to evaluate the applicability of the anammox process to a partially nitrified supernatant coming from the anaerobic digestion of piggery and poultry manures and of agro-wastes. Two critical issues are addressed: 1) solid/liquid separation of the agriculture digestate and 2) the possibility to apply the anammox process to the liquid digestate fraction, after partial nitritation, in spite of the high variability in the characteristics of the agricultural digestate. As for the S/L separation of digested agro-wastes, results suggested that digestate conditioning (coagulants and flocculants) and the usage of a decanter centrifuge are necessary to meet TSS values in the liquid phase suitable for biological processes (~ 1 gTSS L-1). As for the applicability of the anammox process to agricultural digestates, results obtained by operating a SBR and an MBR reactor at increasing percentage of real wastewater in the feed, suggest that both reactor types allowed to support a stable anammox process and could efficiently remove the nitrogen load as soon as the percentage of real wastewater in the feed was up to 70%.