Unraveling the nitrogen removal properties and microbial characterization of "Candidatus Scalindua"-dominated consortia treating seawater-based wastewater.

"Candidatus Scalindua", as known as marine anammox bacteria (MAB), was engineered to remove nitrogen from seawater-based wastewater (SWW). In this study, "Candidatus Scalindua" was successfully enriched within 106 days with marine sediments as inoculated sludge. The operating temperature was 20 ± 2 °C, and influent pH was 7.5 ± 0.1. Ammonia (NH-N) removal rate (ARR) was 0.53 kg/(m·d) with the NH-N loading rate of 0.68 kg/(m·d), and nitrite (NO-N) removal rate (NRR) was 0.57 kg/(m·d) at 0.89 kg/(m·d) NO-N loading rate. Nitrogen removal was negatively affected at an influent NO above 224 mg/L, which decreased the ARR and NRR to 0.36 and 0.31 kg/(m·d), respectively. The genus "Ca. Scalindua" dominated the reactor, and it synergistically coexisted with Marinicella to achieve efficient nitrogen removal. This work would help to better understand the nitrogen removal properties and microbial characterization of MAB in SWW wastewater treatment under low temperature.