Effect of increasing salinity and low C/N ratio on the performance and microbial community of a sequencing batch reactor

ABSTRACT

The purpose of this study was to investigate the effects of increasing salinity on the performance and microbial community structure in a sequencing batch reactor (SBR) treating low C/N ratio wastewater. The SBR was subjected to a gradual increased salinity from 0 wt% to3.0 wt% under low Chemical Oxygen Demand (COD)/N ratio, operating for 80 days. The study results indicated that high salinity decreased the removal efficiency of ammonium (${\mathrm{NH}}_4^{+}\text{-}\mathrm{N}$) from 77.09% (1.0 wt%) to 45.7% (3.0wt%). The organic matter removal are not significantly affected by the high salinity. Non-metric Multi-Dimensional Scaling (NMDS) analysis showed that the gradual increased salinity altered the overall bacterial community structure, and low salinity (1wt%) promoted the bacterial diversity, while high salinity (2 and 3 wt%) significantly decreased the bacterial diversity in low C/N ratio activated sludge system. Further analysis revealed that two genera related to nitrification process (unclassified-Nitrosomonadales and g-Nitrospira) were inhibited, while a genus related to organic removal (Piscicoccus) and three genera related to denitrification (Rodobacteraceae, Denitromonas and Hyphomicrobium) increased significantly at a salinity of 3 wt%. This study provides insights of shifts in the bacteria community under the stress of high salinity in low C/N ratio of activated sludge systems.

GRAPHICAL ABSTRACT

KEYWORDS:

• Activated sludge
• low COD/N ratio
• salinity influence
• sequencing batch reactor
• microbial population

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was supported by the National Key Research and Development Program of China [grant number 2016YFC0401105], the Open Research Fund Program of Key Laboratory of Cleaner Production and Integrated Resource Utilization of China National Light Industry [grant number CP-2018-YB4] and TianJin Municipal Science and Technology Project [grant number 17YFCZZC00490].