Denitrification performance and mechanism of a novel sulfur-based fiber carrier fixed-bed reactor: Co-existence of sulfur-based autotrophic denitrification and endogenous denitrification

Sulfur autotrophic denitrification becomes a research hotspot in recent years, but traditional packed bed reactor has several disadvantages, including small sulfur specific surface area, easy blockage, and sulfur loss when using small sulfur grains. A sulfur-based fiber carrier fixed-bed reactor (SFFR) was developed in the study, which had the advantage of higher denitrification efficiency due to the large sulfur specific surface area, and the nitrogen removal rate (NRR) of it could reach 0.304 kg (NO3-N)/m(3)center dot d. Meanwhile, the sulfur-based fiber filler that used in SFFR had characteristics of high surface roughness and suitable for microbial attachment growth, which promoted the endogenous denitrification in the reactor. Therefore, SAD and endogenous denitrification were jointly involved in nitrate removal in SFFR, and the sulfate productivity gradual decreased to 5.58 mgSO(4)(2-) /mgNO(3)(-)N in this study, which decreased by 26 % compared with the theoretical value (7.54 mgSO(4)(2-) /mgNO(3)(-) -N). The result of this research showed that compared with the traditional SAD process, the electron utilization rate of SFFR increased from 75.76 % to 91.8 %. Meanwhile, the higher electron utilization rate of SFFR indicated that the advantages of SFFR included lower elemental sulfur consumption, lower acid production and smaller sludge production. In addition, the maximum NRR of SFFR was further increased to 0.528 kg (NO3--N)/m(3)center dot d with the assist of vibrating device because it could enhance the mass transfer during the process of wastewater treatment. Microbial analysis suggested that several autotrophic denitrifiers along with heterotrophs and endogenous denitrifiers, co-existed in the biofilm.