Exploration and verification of the feasibility of the sulfur-based autotrophic denitrification integrated biomass-based heterotrophic denitrification systems for wastewater treatment: From feasibility to application

Denitrification Performance in Packed-Bed Reactors Using Novel Carbon-Sulfur-Based Composite Filters for Treatment of Synthetic Wastewater and Anaerobic Ammonia Oxidation Effluent

“…In the first 15 days of period 6, the NRE of the R 1 , R 2 , R 3 , and R 4 reactors was 53.5 ± 3.1%, 66.4 ± 3.6%, 58.9 ± 2.6%, and 70.1 ± 1.9%, respectively; and the NRE of the remaining days of period 6 (days 96–180) in the reactors was 39.5 ± 3.5%, 46.4 ± 2.7%, 41.9 ± 2.6%, and 50.1 ± 1.9%, respectively. This was in accordance with a previous study in packed-bed denitrification systems ( Liang et al, 2021b ). Although the average temperature in the reactors was 31°C during the last few days of period 6, which was closer to the optimum temperature of 35°C for nitrate reduction ( Chen et al, 2018 ) than that in the other periods, the NRE values were still moderate.…”

“…The presence of sulfide might be attributed to the sulfur disproportionation process (Eq. 6), which is induced by the low nitrate load of the influent ( Liang et al, 2021b ). The higher sulfide content in R 1 and R 3 reactors in period 6 may be caused by the uneven distribution of denitrification capacity in the reactors.…”

“…These findings showed that the lower pH could significantly decrease the NRR, although the NRR also declined when the HRT was 3 h, and the decline range was not as large as that with HRT of 1 h. Meanwhile, the increased pH value did not bring better NRR to all the reactors, while only a limited increase in NRR of the R 1 and R 3 reactors was observed. The reason for these phenomena may be attributed to the solubility of the solid-phase filter, and it could be speculated that as the pH decreases, even if the HD caused by the natural solid organic carbon sources can counterbalance a certain drop in pH ( Liang et al, 2021b ), while shell powder would be the major role to slow down the pH drop. As the flow rate in the reactor increased, it was difficult for the solid-phase shell powder to provide sufficient alkalinity to alleviate the drop in pH, and the rapid drop in pH led to a decrease in NRR.…”

An efficient anoxic/aerobic/aerobic/anoxic process for domestic sewage treatment: From feasibility to application

“…A certain amount of COD in O2 could contribute to the occurrence of HD process, while the COD/TIN ratio in O3 was generally lower than 2. Therefore, it was difficult to realize complete HD process in the O3 chamber due to poor COD resources, which could not provide enough electrons ( Liang et al, 2021b ). Aside from COD measurements, it was found that the change of pH value was closely related to the performance of reactor, when the DO concentration was lower than 4 mg L −1 , there were no significant differences in the pH values between the inlet and outlet of chamber O2, and decreased only in the effluents of O3 and A4 ( Figure 2 ).…”

“…Meanwhile, the genera Chujaibacter and Nitrospira were also dominant in chambers O2 and O3, the Nitrospira is known as a nitrification-related bacterium during nitrification process ( Li et al, 2022a ), and Chujaibacter is reported to be positively correlated with Nitrospira ( Sato et al, 2021 ). The presence of genera Bradyrhizobium , Mesorhizobium , Dokdonella , Ferruginibacter , Holophaga , and Hyphomicrobium could be related to the denitrification processes or organic degradation ( Chen et al, 2021 ; Liang et al, 2021b ; Wang et al, 2021b ; Qian et al, 2022 ; Li et al, 2022b ), this is helpful in removing COD and nitrate in the chambers O2 and O3, and the unclassified_f __Comamonadaceae was able to reduce nitrate by using organic carbons ( Zhang et al, 2022 ). In general, the main functions of bacteria in the O2 and O3 chambers may be to get involved in the nitrification process, denitrification process and removal of organic matter, which further verified the removal trend of pollutants in the reactor.…”