Comparison of nitrogen removal and microbial properties in solid-phase denitrification systems for water purification with various pretreated lignocellulosic carriers

•Denitrification efficiency largely affected via various materials and pretreatments.•Acid treatment favored sustainable denitrification and declined effluent NH4+-N.•Higher abundant denitrifiers and fermentative bacteria in pretreated SPD system.

This study explored the water purification performances of solid-phase denitrification systems filled with either untreated, acid and alkali pretreated corncob, rice straw and rice hulls. Nitrate reduction improved via pretreatments was found in ascending order from corncob, rice straw and rice hulls systems due to their various chemical compositions, while the pretreated rice hull systems still had the lowest nitrate reduction efficiencies (<90%). Besides, nitrite accumulation only frequently detected (<0.5 mg L−1) in rice hulls system especially in untreated system, while ammonium occurrences in effluent were much more prevalent in corncob and rice straw systems than those of rice hulls system, and could be impaired via acid pretreatment. Miseq sequencing analysis showed that the higher abundances of dominant denitrifiers (Bosea, Acidovorax, Simplicispira, Dechloromonas, etc.) and fermentative anaerobic bacteria (Actinotalea, Cellulomonas, Opitutus, etc.) co-existed in the pretreated systems than those of none pretreatment, which was vital for efficiently sustainable nitrogen removal.