Denitrification performance and microbial community analysis of sulfur autotrophic denitrification filter for low-temperature treatment of landfill leachate

This study investigated the denitrification performance of sulfur autotrophic denitrification filter (SADF) in five low-temperature ranges (14.0-15.0 celcius, 13.1-13.9 degrees C, 12.0-13.0 degrees C, 10.1-11.9 degrees C and 8.8-9.8 degrees C) environments and the nitrogen removal contribution along the filter cells. Results showed that the average total nitrogen removal efficiency (TNRE) of the bioreactor were 90.06%, 88.49%, 86.61%, 85.71% and 74.54%, respectively. However, when the temperature was lower than 9.8 degrees C, the process of sulfur autotrophic denitrification was obviously inhibited, but the inhibition was slowed down after low-temperature acclimation. The bottom-filter layer (0-200 mm) contributed 50.54% of the nitrogen removal, which was the greatest. The middle- filter layer (400-600 mm), which was at 35.86%, was next. And the upper- filter layer (800-1200 mm) made the least contribution, at 13.60%. It was demonstrated by high-throughput sequencing that in addition to Thiobacillus, the genus Sulfurimonas was also found and its average relative abundance was comparable to the former (24.03% for Thiobacillus and 23.10% for Sulfurimonas). The results of microbial function prediction showed that sulfur and nitrogen metabolism played a key role in nitrogen removal. The study of substrate environmental variables showed that the key bacterial groups of nitrogen removal along the process were negatively correlated with total nitrogen (TN) and positively correlated with pH value.