Nitrification and aerobic denitrification in solid phase denitrification systems with various biodegradable carriers for ammonium-contaminated water purification

BACKGROUND Solid phase denitrification (SPD) has achieved efficient performance mostly under anoxic conditions for nitrate reduction, while it has few applications in achieving simultaneous nitrification and denitrification (SND) for ammonium nitrogen (NH4+-N)-rich water treatment. This study attempted to develop aerobic SPD systems with three alkali-pretreated biodegradable carriers (rice husk, pomelo peel and durian peel). RESULTS The three carriers all achieved much higher average nitrogen removal rates (0.56-0.68 mg NH4+-N L-1 h(-1), 0.06-0.50 mg total nitrogen (TN) L-1 h(-1)) than those of the control reactor without carriers (0.18 mg NH4+-N L-1 h(-1), <0.01 mg TN L-1 h(-1)) at a dissolved oxygen (DO) concentration of 2.5 mg L-1, and no decline in SND efficiency occurred when the DO level increased to 7.5 mg L-1. However, the aerobic denitrification efficiency was reduced with declining organic availability of the biodegradable carrier. Durian peel carrier exhibited the most efficient TN removal performance and the longest efficiently stable stage owing to its higher carbon content, and a lower DO concentration of 2.5 mg L-1 was helpful for achieving a longer efficiently stable stage. There were significant differences in the dominant bacteria attached to the three biofilm carriers. Meanwhile, higher enrichment of nirS-type than nirK-type denitrifier diversity was found, especially at a higher DO level, and 18 new aerobic denitrifiers were identified. CONCLUSION The aerobic SPD system could achieve efficient nitrification and denitrification, which was strongly affected by the organic availability of the biodegradable carrier. Therefore, aerobic SPD could be considered as an attractive technology for nitrogen removal in ammonium-rich water and wastewater. (c) 2019 Society of Chemical Industry