This study emphasizes on the cellulase production characteristics of strain ZY7 and its collaboration with nitrate-dependent ferrous oxidizing (NFO) strain XL4 to achieve efficient denitrification at low carbon-to-nitrogen (C/N) ratio. Results indicated that the denitrification efficiency increased from 65.47 to 97.99% at 24 h after co-culture at C/N of 1.0. Three-dimensional fluorescence excitation-emission matrix (3D-EEM) showed significant changes in the intensity of soluble microbial products (SMP), fulvic-like materials, and aromatic proteins after co-culture. Bio-precipitates were characterized by Scanning electron microscope (SEM), Fourier transform infrared spectrometer (FTIR), and X–ray diffraction (XRD), which showed that cellulose structure was disrupted and the metabolites were potential carbon source for denitrification. In addition, cellulase activity suggested that the hydrolysis of β-1,4-glycosidic bonds and oligosaccharides may be the rate-limiting steps in cellulose degradation. This work promoted the understanding of denitrification characteristics of co-culture and expanded the application of cellulose degrading bacteria in sewage treatment.
A two-chamber microbial photoelectrochemical cell (MPEC) with a denitrification biocathode and an α-Fe 2 O 3 /P3HT photoanode was established aimed to enhance nitrate removal from wastewater of low carbon sources and achieve simultaneous ibuprofen degradation. The results demonstrated that the average removal of NO 3 – -N in the biocathode reached 96.56 ± 0.72% when the COD/NO 3 – -N was 0.75, and the relative contributions of heterotrophic and autotrophic denitrification were 21.47% and 78.53%, respectively. When there was no organic source in the influent, the maximum removal of NO 3 – -N was less than 45%. High-throughput sequencing revealed that both heterotrophic bacteria, such as Bacillus , and autotrophic bacteria (e.g., Thermomonas and Hydrogenophaga ) dominated in the cooperative denitrification biocathode. Moreover, the functional gene analysis showed that the abundance of genes related to denitrification was highest in the cooperative denitrification biocathode. In addition, the photocatalytic degradation efficiency of ibuprofen in the anode chamber attained 67.95% ± 0.97%.
Traditional heterotrophic denitrification encounters challenges in the treatment of wastewater with a low carbon to nitrogen ratio (C/N). This study successfully achieved complete nitrogen removal with energy efficiency through the anaerobic-anoxic-anoxic sulfur autotrophic (A 3 ) process in the treatment of low C/N wastewater. Notably, this process enabled simultaneous nitrification-heterotrophic denitrification (SND) coupled with sulfur-driven autotrophic denitrification (SAD) with a nitrogen removal rate of 0.15 kg N/m 3 /d (100 % of NH 4 + -N and 92 % of total nitrogen (TN) removal). More than 85 % of TN removal and 50 % of SND contribution were obtained under low-temperature conditions (about 10–14 °C). After cultivation in the A 3 system, the dominant bacterial genus changed from norank_f__Saprospiraceae (11.22 %–5.21 %) to Ferruginibacter (0.89 %–19.31 %). Additionally, Nitrospira (1.34 %) and Thiobacillus (2.14 %) exhibited a synergistic effect in the anoxic tank, collectively promoting the simultaneous nitrification and denitrification process. This study proposes a novel and energy-efficient approach for the treatment of low C/N wastewater.
Yi Sun,Junfeng Su,Amjad Ali,Tinglin Huang,Shuai Zhang,Yitian Min
The coexistence of multiple pollutants and lack of carbon sources are challenges for the biological treatment of wastewater. To achieve simultaneous removal of nitrate (NO 3 − -N) and cadmium (Cd 2+ ) at low carbon to nitrogen (C/N) ratios, 2-hydroxy-1,4-naphthoquinone (HNQ) was selected from three redox mediators as an accelerator for denitrification of heterotrophic strain Pseudomonas stutzeri sp. GF2 and autotrophic strain Zoogloea sp. FY6. Then, halloysite nanotubes immobilized with 2-hydroxy-1,4-naphthoquinone (HNTs-HNQ) were prepared and a bioreactor was constructed with immobilized redox mediator granules (IRMG) as the carrier, which was immobilized with HNTs-HNQ and inoculated with the two strains. The immobilized HNQ and the inoculated strains jointly improved the removal ability of NO 3 − -N and Cd 2+ and the removal efficiency of NO 3 − -N (25.0 mg L −1 ) and Cd 2+ (5.0 mg L −1 ) were 92.81% and 93.94% at C/N = 1.5 and hydraulic retention time (HRT) = 4 h. The Cd 2+ was removed by adsorption of iron oxides (FeO(OH) and Fe 3 O 4 ) and IRMG. The electron transport system activity (ETSA) of bacteria was improved and the composition of dissolved organic matter in the effluent was not affected by HNQ. The HNQ promoted the production of FeO(OH) and up-regulated the proportion of Zoogloea (54.75% in the microbial community), indicating that Zoogloea sp. FY6 was dominant in the microbial community . In addition, HNQ influenced the metabolic pathways and improved the relative abundance of some genes involved in nitrogen metabolism and the iron redox cycle.
危险品化学品经营许可证（带存储）