Abundance, community structures, and nitrification inhibition on ammonia-oxidizing archaea enriched under high and low salinity

This study investigated the effect of salinity on ammonia-oxidizing archaea and bacteria (AOA and AOB) by operating two bioreactors under the salinity level of 2.5‰ and 35‰, respectively. Both bioreactors achieved more than 95% of nitrification efficiency, but distinct AOA and AOB populations were enriched in the two bioreactors. For AOB, Nitrosomonas marina-like AOB and Nitrosomonas oligotropha-like AOB were dominated in high- and low-salinity bioreactors, respectively, while two different AOAs in marine group were dominated in high- and low-salinity bioreactors, respectively. The results from the amoA gene based real-time quantitative polymerase chain reaction indicated that, after 150 days of operation, AOA was more abundant than AOB by 1.6–54 and 2.3–81.1 times in the high and low salinity bioreactors, respectively. The results of inhibitory tests for seven chemicals on AOA-enriched sludge showed that 0.5 mg/L of phenol, benzene, toluene, and pyridine caused more than 55% of nitrification inhibition on AOA-enriched sludge. In comparison with AOB, AOA, however, showed higher tolerance to dimethyl sulfide and allylthiourea. Ethylenediamine presented a similar inhibitory effect on AOA and AOB.