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Anaerobic ammonium oxidation (anammox), as an efficient and low-carbon method for nitrogen removal from wastewater, faces the challenge of slow enrichment of functional bacteria. In this study, the enrichment of anammox bacteria Candidatus Brocadia was successfully accelerated by co-culturing with the quorum-sensing strain Pseudomonas aeruginosa and anoxic sludge from a pig farm. Experimental results showed that the R2, which had Pseudomonas aeruginosa added, exhibited chemical reaction ratios RS (NO2−-N consumption/NH4+-N consumption) and RP (NO3−-N production/NH4+-N consumption) closer to the theoretical values of the anammox reaction since Phase Ⅱ. Bacterial community analysis indicated that the abundance of Candidatus Brocadia in R2 reached 1.63% in cycle 20, significantly higher than the 0.45% in R1. More quorum-sensing signaling molecules, primarily C6-HSL, were detected in R2. C6-HSL was positively correlated with processes such as the secretion of anammox extracellular polymers (EPS) and the regulation of nitric oxide reductase (Nir), which may explain the reason behind the accelerated increase in the abundance of Candidatus Brocadia through co-culturing. Moreover, the metabolism of the dominant genus Paracoccus within the two groups of reactors also showed positive regulation by C6-HSL, with its abundance trend similar to that of Candidatus Brocadia, jointly completing the nitrogen removal process in the reactors. However, it is still unknown which genera secrete large amounts of C6-HSL after inoculation with Pseudomonas aeruginosa. This research provides a novel and low-cost method for the enrichment of anammox bacteria. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N2O) is not only recognized as a potent greenhouse gas, but it is also used in industry as a clean energy source. In this study, different electrode materials of carbon felt and graphite were equipped in the ΔnosZ P. aeruginosa/microbial electrolysis cell (MEC) systems to explore the optimization mechanism for long-term N2O recovery during incineration leachate treatment. The carbon felt group showed a better performance in N2O recovery across 45 days of operation. The N2O conversion efficiency was above 80% and the proportion of N2O in biogas accounted for 80.6% in the carbon felt group. qRT-PCR analysis was conducted to evaluate the expression of genes involved in denitrification (norB) and electroactivity (phzG, phzM, and phzH) of ΔnosZ P. aeruginosa. The results showed a significant upregulation in the suspended biomass (day 21) and the electron-attached biomass (day 45) from the carbon felt-equipped reactor, which was highly related to the opportunity of biomass exposed to the phenazine derivatives. By the carbon felt optimization in the system, 82.6% of the Pseudomonas genus survived after 45 days of operation. These results indicate that the carbon felt electrode has a more sustainable performance for N2O recovery in the ΔnosZ P. aeruginosa/MEC system. [ABSTRACT FROM AUTHOR]