Insights into nitrogen removal and microbial response of marine anammox bacteria-based consortia treating saline wastewater: From high to moderate and low salinities

Bioaugmentation using HN-AD consortia for high salinity wastewater treatment: Synergistic effects of halotolerant bacteria and nitrogen removal bacteria

Bioaugmentation shows promise in enhancing nitrogen removal efficiency of high-salt wastewater, yet the impact of microbial associations on ecosystem function and community stability remains unclear. This study innovatively introduced a novel heterotrophic nitrification-aerobic denitrification bacterial consortium to improve the performance of SBR reactor for removing nitrogen from saline wastewater. The results revealed that the bioaugmented reactor (R2) exhibited superior removal performance, achieving maximum removal efficiencies of 87.8 % for COD and 97.8 % for NH4+-N. Moreover, proper salinity (2 % and 4 %) promoted the secretion of EPS and ectoine, further enhancing the resistance and stability of bacterial consortia. 16S rRNA gene sequencing and metagenomics analysis revealed the key denitrifying bacteria Pseudomonas and salt-tolerant bacteria Halomonas were successfully coexistence and the relative abundances of crucial genes (napB, nirS, norB, norC and nosZ) were increased obviously, which were benefit for the excellent nitrogen removal performance in R2. These findings elucidate microbial interactions in response to salinity in bioaugmentation, providing a valuable reference for the efficient treatment of high-saline wastewater.

Characteristics and Mechanisms of Simultaneous Quinoline and Ammonium Nitrogen Removal by a Robust Bacterium Pseudomonas stutzeri H3

The discharge of organic and inorganic nitrogenous pollutants in wastewater leads to eutrophication and disrupts the ecological balance. Therefore, the pressing need for an effective treatment method has become increasingly evident. A robust bacterium Pseudomonas stutzeri H3 capable of simultaneous organic and inorganic nitrogen removal was isolated from the activated sludge in the coking wastewater treatment system. The optimal conditions for the simultaneous removal of ammonium nitrogen and quinoline were as follows: C/N ratio of 15-20, initial pH of 7-8, culture temperature of 30 °C, and shaking speed of 150-300 rpm. At 200 mg/L ammonium nitrogen and 100 mg/L quinoline, strain H3 achieved above 90% of removal efficiency, exhibiting excellent simultaneous nitrogen removal capabilities. The outstanding nitrogen removal efficiencies in the presence of quinoline and different inorganic nitrogen sources further confirmed the simultaneous organic and inorganic nitrogen removal capability of strain H3. The whole genome sequencing and nitrogen metabolic intermediates determination of strain H3 were performed to elucidate the gene function annotations, nitrogen removal function genes, and nitrogen metabolic pathways. The findings provide a promising pathway to treat the organic and inorganic nitrogenous pollutants in wastewater.

In situ remediation of eutrophic Wolong Lake sediments using novel PVA-SA-biochar and PVA-SA-zeolite embedded immobilized indigenous microorganisms: a pilot study

Sediment restoration has become a key link in river and lake pollution control. This present study investigated the selection of dominant microbial bacteria, the selection and optimization of microbial immobilized carrier materials, and the effect of embedded immobilized microbial in situ remediation of bottom sediments based on the actual restoration pilot project of eutrophic Wolong Lake. The composite of denitrifying and photosynthetic bacteria at a ratio of 1 : 2 showed the best performance with COD, TN, and TP removal efficiencies of 74.86%, 65.2%, and 67.5%, respectively. Denitrifying bacteria to photosynthetic bacteria optimal composite bacterial solutions with polyvinyl alcohol-sodium alginate (PVA-SA), PVA-SA-zeolite and PVA-SA-biochar carriers were selected, and the effects of different carriers were analyzed and compared in terms of multiple characteristics. PVA-SA-biochar carriers showed the best ammonia-nitrogen transfer performance, mass transfer coefficient (0.681 × 10-9 m2 s-1), specific surface area (76.3 m2 MB g-1) and performed best in mechanical strength and chemical stability. The effects of biochar, PVA and SA contents on COD removal (Y) were analyzed using the 3D-response surface methodology. Biodegradation capacity (G-value) increased from 0.68 × 10-3 kg (kg h)-1 at the beginning of the test to 2.32 × 10-3 kg (kg h)-1 after 80 days of the remediation test with a growth rate of 258.82%. The water quality index has significantly improved, indicating a good restoration effect. Alpha diversity analysis showed that the Shannon and Simpson indexes increased and decreased. The relative abundance of Bacteroidota, Proteobacteria, Planctomycetota and Chloroflexi, closely related to the denitrification, decarbonization and phosphorus removal, increased while Chloroflexi decreased compared with before restoration. Embedded immobilized microbial technology significantly enhances the quality of sediment mud and the overlying water. In the long term, this approach does not release toxic substances into water bodies, thus fostering biodiversity and promoting ecological restoration. It represents a novel restoration strategy that contributes positively to environmental sustainability.

Tracking the nitrogen transformation in saline wastewater by marine anammox bacteria-based Fe(II)-driven autotrophic denitratation and anammox

Marine anammox bacteria-based Fe(II)-driven autotrophic denitratation and anammox (MFeADA) was investigated for nitrogen removal from saline wastewater for the first time. The study demonstrated that varying influent doses of Fe(II), which participate in the Fe cycle, significantly influenced nitrogen removal performance by altering the fate of nitrite. When 50 mg/L Fe(II) was added, the nitrogen removal was mainly performed by the anammox and Fe(II)-driven autotrophic denitratation (FeAD). As the Fe(II) rose to 100-150 mg/L, the anammox, FeAD and Feammox mainly occurred. Optimal nitrogen removal efficiency, reaching 93 %, was achieved at an influent Fe(II) concentration of 150 mg/L. As the Fe(II) reached 250 mg/L, however, nitrate was directly reduced to dinitrogen gas by the excessive Fe(II) through the Fe(II)-driven autotrophic denitrification (FeADN). Candidatus Scalindua (4.1 %), Marinicella (5.3 %) and SM1A02 (31.8 %) were the dominant functional microbes. In addition, the normalized nitrate reductase abundance was about 3.1 times that of nitrite reductase, leading to the occurrence of FeAD, which achieved a stable nitrite supply for marine anammox bacteria. This novel study can promote the practical implementation of the MFeADA process in nitrogen-laden saline wastewater treatment.

Long-term effect of phenol, quinoline, and pyridine on nitrite accumulation in the nitrification process: performance, microbial community, metagenomics and molecular docking analysis

Phenol, quinoline, and pyridine, commonly found in industrial wastewater, disrupt the nitrification process, leading to nitrite accumulation. This study explores the potential mechanisms through which these biotoxic organic compounds affect nitrite accumulation, using metagenomic and molecular docking analyses. Despite increasing concentrations of these compounds from 40 to 160 mg/L, ammonia nitrogen removal was not hindered, and stable nitrite accumulation rates exceeding 90 % were maintained. Additionally, these compounds inhibited nitrite-oxidizing bacteria (NOB) and enriched ammonia-oxidizing bacteria (AOB) in situ. As the concentration of these compounds rose, protein (PN) and polysaccharide (PS) concentrations also increased, along with a higher PN/PS ratio. Metagenomic analysis further revealed an increase in hao relative abundance, while microbial community analysis showed increased Nitrosomonas abundance, which contributed to nitrite accumulation stability. Molecular docking indicated that these compounds have lower binding energy with hydroxylamine oxidoreductase (HAO) and nitrate reductase (NAR), theoretically supporting the observed sustained nitrite accumulation.

Enrichment of marine microbes to remove nitrogen of urea wastewater under salinity stress

Salinity (NaCl) and urea concentration significantly affect the diversity, structural and physiological function of microbial communities in the biological treatment of wastewater. However, the responses of microbial in high salt and urea wastewater remain elusive. Here, we investigated microbial community function and assembly of four regions using gradient domestication experiment combined with 16S rRNA gene sequencing and statistical methods. The results showed that with the increase of salinity and urea concentration, the consortium Xiamen could still remove most urea, while the other three consortia could not. The alpha diversity of microbial community initially decreased and then increased, showing a recovery trend. After domestication, the consortium Xiamen exhibited high physiological activity and complex network structure, and the community assembly process changed from stochastic to deterministic during the domestication. Furthermore, the keystones with low abundance were associated with urea removal and important for maintain the complexity of the networks, while Arenibacter and Oceanimonas were found to be keystones in maintaining efficient urea removal in harsh environments. To sum up, environmental effects dominated by salinity and urea concentration stress drove the community assembly and species coexistence that underpinned the microbial differentiation pattern at a geographic scale. These results provided new sights for elucidate how microbial response to salinity and urea during wastewater treatment.

Deciphering performance and microbial characterization of marine anammox bacteria-based consortia treating nitrogen-laden hypersaline wastewater: Inhibiting threshold of salinity

Hypersaline wastewater posed a challenge to microbial nitrogen removal processes. Herein, halophilic marine anammox bacteria (MAB) were applied to treat nitrogen-rich wastewater with 35-90 g/L salts for the first time. It was found that MAB, with low relative abundance (2.3-6.9 %), still exhibited good nitrogen removal efficiency (>90 %) under 35-70 g/L salts. The specific anammox activity peaked at 180.16 mg N/(g·VSS·d) at 65 g/L salts. MAB secreted more extracellular polymeric substances to resist the adverse effects of hypersaline stress. Nevertheless, the nitrogen removal deteriorated at 75 g/L salts, and further collapsed as the salinity increased. At 90 g/L salts, total nitrogen removal rate decreased by 74 % compared with that of 35 g/L salts. Besides, SBR1031 increased from 12.0 % (35 g/L salts) to 17.4 % (90 g/L salts) and became the dominant bacterial genus in the reactor. This work shed light on the treatment of hypersaline wastewater through MAB.

Response of marine anammox bacteria to long-term hydroxylamine stress: Nitrogen removal performance and microbial community dynamics

The response of anammox bacteria to hydroxylamine has not been well explained. Herein, hydroxylamine was long-term added as the sole substrate to marine anammox bacteria (MAB) in saline wastewater treatment for the first time. MAB could tolerate 5 mg/L hydroxylamine. However, MAB activity was inhibited by the high dose of hydroxylamine (40 mg/L), and hydroxylamine removal efficiency was only 3 %. Remarkably, when hydroxylamine reached 20 mg/L, ammonium was produced the most at 2.88 mg/L, mainly by the hydroxylamine and hydrazine disproportionations. Besides, the relative abundance of Candidatus Scalindua decreased from 4.6 % to 0.6 % as the hydroxylamine increased from 0 to 40 mg/L. MAB secreted more extracellular polymeric substances to resist hydroxylamine stress. However, long-term hydroxylamine loading led to the disintegration of MAB granules. This work shed light on the response of MAB to hydroxylamine in saline wastewater treatment.