Comparison of Denitrification Performance and Regulation Strategies of Corncob/PHBV and Sulfur in Circulation Packed-Bed Reactor

To enhance nitrogen removal in low-carbon sewage through heterotrophic and sulfur autotrophic denitrification, a corncob-sulfur circulating packed-bed reactor (CS-CPBR) and a PHBV-sulfur circulating packed-bed reactor (PS-CPBR) were constructed. The results showed that the total nitrogen (TN) and NO 3 − -N removal efficiencies of both reactors improved with increasing hydraulic retention time(HRT) and NaHCO 3 dosage. With a HRT of 2 h, a NaHCO 3 dosage of 0.4 g/L, and an influent NO 3 − -N concentration of 30 mg/L, the TN removal efficiencies were 87.9% and 94.0%, respectively. The PS-CPBR exhibited a higher nitrogen removal rate and efficiency. Mechanistic studies indicated that the lower bioavailability of corncob restricted microbial activity in the CS-CPBR, leading to the difference in denitrification efficiency between the two reactors. Metagenomic analysis revealed that, relative to the CS-CPBR, the PS-CPBR significantly enriched denitrifying bacterial genera such as Sinirhodobacter , Rhodobacter , and Brachymonas . The PS-CPBR also harbored higher abundances of denitrification genes ( nirS , norC , nosZ ), thereby strengthening the complete denitrification pathway. This study provides experimental data to guide carbon source selection and process control for solid carbon-sulfur denitrification in advanced nitrogen removal.