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 NO3−-N removal efficiencies of both reactors improved with increasing hydraulic retention time(HRT) and NaHCO3 dosage. With a HRT of 2 h, a NaHCO3 dosage of 0.4 g/L, and an influent NO3−-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.
Gao et al. (Tue,) studied this question.