Startup of pilot-scale single-stage nitrogen removal using anammox and partial nitritation (SNAP) reactor for waste brine treatment using marine anammox bacteria.

This study is the first to demonstrate the startup of a pilot-scale single-stage nitrogen removal using anammox and partial nitritation (SNAP) reactor utilizing marine anammox bacteria. A complete mixing type reactor, continuously fed with waste brine obtained from a natural gas plant (salinity 3%, NH4+-N 130–180 mg/L) and having an effective volume of 2 m3, achieved stable operation at temperatures of 20–30°C with a maximum nitrogen removal rate of 1.43 kg-N/m3/day. During the startup process, along with a small amount of seed sludge, granular sludge was additionally inoculated as a biomass carrier for the enrichment of ammonia oxidizing bacteria (AOB), followed by the enrichment of anammox bacteria. A mesh screen equipped at the outlet of the reactor facilitated the successful sludge retention in the reactor. Analysis of bacterial community composition indicated that Candidatus Scalindua was successfully enriched in the pilot SNAP reactor. These methods for stable sludge retention in the reactor greatly contributed to the startup of the first pilot-scale SNAP reactor using marine anammox bacteria.