Application of anammox within an integrated approach to sustainable food waste management and valorization

Abstract

In this study, the anammox process was applied for the first time to the treatment of ammonium-rich liquid residues produced by the two-stage anaerobic digestion of food waste (2sAD-FW); such residues may represent a significant environmental issue if not properly managed. A granular anammox reactor was fed with a progressively increasing share of partially nitritated 2sAD-FW wastewater. An alternative operating strategy based on partial by-pass of the partial nitritation unit was tested, in order to regulate the influent NO2/NH4 molar ratio without chemical addition. High nitrogen removal efficiency (89±1%) and negligible nitrite discharge rates were achieved, together with high nitrogen removal rate / nitrogen loading rate (NRR/NLR, 97±1%) and stable specific anammox activity (0.42±0.03 gN2-N/gVSS•d). The observed NH4removed/NO2-removed/NO3-produced molar ratio was in agreement with anammox stoichiometry, as confirmed by the low contribution (< 5%) of denitrification to nitrogen removal. Moreover, the possibility of using digital color characterization of granular biomass as a novel, simple tool for the monitoring of anammox biomass enrichment and process performance was investigated under dynamic conditions, using real wastewater: changes in granule color correlated well with the increasing share of 2sAD-FW wastewater in the influent (R 2 =83%), as well as with the decrease of anammox biomass abundance in the reactor (R 2 =68%). The results suggest that anammox may be successfully integrated into a 2sAD-FW system, thus enhancing its environmental sustainability.

A Review on the Challenges and Choices for Food Waste Valorization: Environmental and Economic Impacts

“…129 However, in a two-stage AD process, the methane yield varied from 180−732 mL/g-VS depending on the conversion rate of VS. 130 A high nitrogen removal (89%) has been achieved in a two-stage AD process of FW where partially nitrated wastewater of the AD process was fed, thus enhancing the environmental sustainability of the AD process of FW. 131 In addition, codigestion for the condensate of the FW drying process and sludge from wastewater treatment plant increased the methane yield (72.5%) of activated sludge because of the increased carbon−nitrogen ratio, which resulted from the higher carbon−nitrogen ratio in the condensate. 132…”