Harnessing indigenous quorum sensing bacteria for improved anammox bioreactor startup and nitrogen removal

Anammox bioreactors face challenges of prolonged startup times and sensitivity to environmental fluctuations. Although quorum sensing (QS) has emerged as a potential solution, most studies rely on expensive N-acyl homoserine lactones. This study explored an alternative by isolating indigenous QS bacteria from anammox granules and evaluating their impact on bioreactor performance. Four QS isolates- Ensifer sp. CH9, Brucella sp. CH10, Pseudomonas sp. CH11 and Burkholderia sp. CH12 -were immobilized and introduced into anammox bioreactors. The QS bacteria improved nitrogen removal efficiency, enhanced system stability under an increased nitrogen loading rate (NLR) during start-up. Meanwhile, the bacteria significantly increased production of extracellular polymeric substances and facilitated sludge granulation. Candidatus Brocadia dominated the microbial community in the bioreactors. Additionally, the microbial community structure dynamics were driven by NLR and time rather than QS bacteria. This study highlights indigenous QS bacteria as a cost-effective strategy to improve anammox bioreactor startup and stability.