Elucidating salinity adaptation and shock loading on denitrification performance: Focusing on microbial community shift and carbon source evaluation

Abstract

To understand the denitrification efficiency and microbial community shift with increasing salinity in salinity adaptation and shock loading process, nitrate (NO3–-N), nitrite (NO2–-N) and chemical oxygen demand (COD) removal efficiencies were monitored feeding acetate and primary sludge fermentation liquid. During adaptation process, salinity had little effect on NO3–-N removal efficiency (>99.0%) with acetate-fed, while for fermentation liquid-fed, it decreased to around 97% at high salinity (>2.5%). Effluent NO2–-N was lower than 0.1 mg/L, though obvious fluctuation of NO2–-N was observed with fermentation liquid-fed when salinity change. During shock loading process, denitrification process all had slight decrease when the salinity abruptly increased to 5.0%. Traditional denitrifier of Thauera was the dominant genus, and a specialized microbial community of Azoarcus in salinity adaptation and Paracoccus in shock loading for denitrification showed high salinity tolerant. Meanwhile, microbial diversity was enriched with fermentation liquid-fed at high salinity condition.