Simultaneous ammonium removal and methane production against nitrite inhibition by coupling anammox bacteria activity in biogas digester

Biogas fermentation is a widely used technology of commercial and environmental importance, but the presence of nitrogenous compounds can strongly impact reactor productivity. Here, we investigated methane production in the presence of nitrite inhibition. The effects of lactate, glucose, acetate, formate and maize silage were evaluated. Methane production depended on substrate type, substrate concentration, and the buffer system. Nitrite inhibited methane production, but amendment with anammox bacteria mitigated this inhibition, resulting in 81.1 % recovery of methanogenic activity. Furthermore, anammox bacteria were efficient in removing nitrogenous compounds. A microbial community analysis showed significant shifts depending on the applied conditions, suggesting that a syntrophic relationship of Anaerolinaceae with Methanosaeta, Methanoculleus or Methanospirillum played a crucial role in methanogenesis via the acetoclastic and hydrogenotrophic pathways. These findings can help with stabilizing reactors for methane production and emission reduction.