Effects of salinity on new biological nitrogen removal technology: a review

In recent years, new biological denitrification technologies have been widely concerned in the treatment of high-salt wastewater containing nitrogen. It can tolerate certain salinity and remove nitrogen from wastewater at the same time, which overcomes the drawbacks of traditional biological denitrification, such as large floor space, long process flow and high operating cost. This paper reviews the effects of salinity on new denitrification technologies based on nitrification and denitrification biochemical processes [simultaneous nitrification-denitrification and shortcut nitrification-denitrification) and new denitrification technologies based on anaerobic ammonium oxidation (anaerobic ammonia oxidation, partial nitrification-anammox process, completely autotrophic nitrogen-removal over nitrite (CANON), oxygen-limited autotrophic nitrification-denitrification (OLAND)]. Through literature research, it is found that within the salinity tolerance range, the new technologies have little influence on the denitrification performance, even improve the denitrification performance, and when it exceeds a certain range, it significantly inhibits the nitrogen removal performance of the new technologies. This is mainly due to the influence of salinity on the interaction of multiple microorganisms and their own activities in the new technologies. Adding halophilic bacteria and microorganisms acclimated to a certain salinity in the reactor can treat nitrogen-containing wastewater with higher salinity. Finally, it is pointed out that strengthening the study on the influence of salinity on the microbial community structure and metabolic pattern in the new denitrification process, screening and applying of the salt-tolerant denitrifying microorganisms, and the response mechanism of microorganisms for salt tolerance are the fundamentals to improve the treatment performance of their own processes, which have become the research directions for treatment of high-salt wastewater containing nitrogen. © 2021, Chemical Industry Press Co., Ltd. All right reserved.