Performance stability of partial nitritation/anammox process in treating food waste digestate: NOB inhibition and microbial interactions

Disruption of microbial community stability induced by organic matter presents key challenges in applying the anammox process to treat food waste digestion (FWD). In this study, the proliferation of nitrite-oxidizing bacteria (NOB) led to the collapse of the partial nitritation/anammox (PN/A) process, resulting in a reduction of nitrogen removal efficiency (NRE) to 21.6% in the treatment of FWD. Treatment with in-situ free ammonia (15–20 mg/L) and ex-situ free nitrite acid (10 μg/L) slightly inhibited the activity of NOB during the first 8 days. However, NOB rapidly exhibited adaptive tolerance to the two types inhibition, accompanied by a decrease in anammox activity. qPCR results confirm that the decrease in ammonia-oxidizing bacteria (AnAOB) and the increase in denitrifying bacteria (DB) are another key factors influencing the stability of PN/A process. The anaerobic cultivation mode induced inhibition of NOB, with the abundance of Nitrospira decreasing to 0.09%. Simultaneously, AnAOB underwent significant species evolution: Ca . Brocadia increased from 0.15% to 5.76%, leading to enhanced AnAOB (including Ca . Kuenenia ) utilization of NO 2 − -N. This study provides valuable insights into overcoming the challenges associated with NOB and heterotrophic bacterial proliferation during FWD treatment in the PN/A process. • Low FA and FNA levels inhibit AnAOB and promote rapid NOB tolerance to FA and FNA. • Anaerobic cultivation induced NOB inhibition and AnAOB species evolution. • Large particle size sludge (329-508 μm) favors PN/A sludge retention during inhibition • Ecological balance between Ca. Brocadia and Ca. Kuenenia ensures stable FWD treatment.