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Li S, Yang H. Optimizing denitrification with volatile fatty acids from hydrolysis acidification-treated domestic wastewater: Comparative effects of nitrate and nitrite using immobilized biofiller. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2025; 378:124812. [PMID: 40043563 DOI: 10.1016/j.jenvman.2025.124812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2024] [Revised: 12/29/2024] [Accepted: 03/01/2025] [Indexed: 03/16/2025]
Abstract
By embedding immobilized biofiller, 100% denitrification efficiency was achieved with nitrate or nitrite as electron acceptors utilizing volatile fatty acids (VFAs) from domestic wastewater after hydrolysis acidification. The consumption patterns of VFAs by functional bacteria and differences in nitrogen metabolic gene expression were thoroughly analyzed. Total consumption of acetic and propionic acids with >95% VFAs utilization was achieved utilizing nitrate, whereas the consumption of butyric and valeric acids was enhanced utilizing nitrite. Denitrification-related genes were all upregulated, particularly nosZ, indicating systemic N2O emission reduction potential. Electron acceptor changes dynamically shifted microbial dominance from Thauera (19.4%) to Thiobacillus (7.2%). These results provide valuable insights into the adaptability and ecological niche characterization of denitrifying bacteria, contributing to improving nitrogen removal efficiency, optimizing carbon source utilization, and reducing sludge production.
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Affiliation(s)
- Siqi Li
- Key Laboratory of Beijing for Water Quality Science and Water Environmental Recovery Engineering, College of Architectural Engineering, Beijing University of Technology, Beijing, 100124, China
| | - Hong Yang
- Key Laboratory of Beijing for Water Quality Science and Water Environmental Recovery Engineering, College of Architectural Engineering, Beijing University of Technology, Beijing, 100124, China.
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2
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Wan P, Liu Y, Li B, Yu X, Jiang L, Lv W. Yeast-enhanced activated sludge for improved nitrogen removal in wastewater treatment: Focus on dissolved organic nitrogen degradation. ENVIRONMENTAL RESEARCH 2024; 263:120181. [PMID: 39424030 DOI: 10.1016/j.envres.2024.120181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2024] [Revised: 09/18/2024] [Accepted: 10/16/2024] [Indexed: 10/21/2024]
Abstract
Dissolved organic nitrogen (DON) in effluent of wastewater treatment plants (WWTP), particularly hydrophilic DON, is usually more effective than dissolved inorganic nitrogen (DIN) in stimulating phytoplankton growth and increases the risk of eutrophication in receiving waterbodies. Proteins, amino acids, and nucleic acids, which are the main sources of DON in the effluent, are produced during the hydrolysis of extracellular polymeric substances (EPS) in activated sludge. Herein, a yeast strain Candida tropicalis O2, which was highly efficient in degrading DON in EPS was screened. Within 48-h batch experiments, the DON removal rates of the extracted hydrophilic and hydrophobic EPS reached 68.26% and 59.27%, respectively. During the continuous 35-day operation of sequencing batch bioreactor (SBR) fed with synthetic wastewater, the yeast-enhanced activated sludge (AS-Y) reactor demonstrated a marked improvement in removing various pollutants compared to the traditional activated sludge (AS) reactor. Specifically, DON removal increased by 1.53 mg/L (24.75%), hydrophilic DON by 1.24 mg/L (27.13%), hydrophobic DON by 0.28 mg/L (12.08%), and COD removal by 4.04 mg/L (6.48%). Although the DIN removal decreased by 0.38 mg/L (3.86%), it did not attenuate the overall TN removal from the system, and an additional TN reduction of 1.15 mg/L (7.13%) was achieved. Metagenomic analysis showed that adding strain O2 slightly inhibited the DIN metabolism, and the relative abundances of napB, nirK/S, norB/C, and nosZ involved in denitrification somewhat decreased. Kyoto Encyclopedia of Genes and Genomes and Carbohydrate-Active Enzymes annotations revealed that adding strain O2 promoted amino acid and carbohydrate metabolism. The increased relative abundance of Candida indicated that strain O2 was able to colonize the sludge in AS-Y reactor, which was conducive to synergistic interactions with other microorganisms. This study provided a novel method for in situ improving nitrogen removal in WWTP and reducing the eutrophication risk of the effluent to receiving waterbodies.
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Affiliation(s)
- Pengfei Wan
- School of Civil & Environmental Engineering and Geography Science, Ningbo University, Ningbo, 315211, China
| | - Ying Liu
- School of Civil & Environmental Engineering and Geography Science, Ningbo University, Ningbo, 315211, China
| | - Bo Li
- School of Civil & Environmental Engineering and Geography Science, Ningbo University, Ningbo, 315211, China
| | - Xiao Yu
- School of Civil & Environmental Engineering and Geography Science, Ningbo University, Ningbo, 315211, China
| | - Li Jiang
- School of Civil & Environmental Engineering and Geography Science, Ningbo University, Ningbo, 315211, China
| | - Wenzhou Lv
- School of Civil & Environmental Engineering and Geography Science, Ningbo University, Ningbo, 315211, China.
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Kou L, Huang T, Zhang H, Wen G, Li K. Aerobic denitrifying bacterial community with low C/N ratio remove nitrate from micro-polluted water: Metagenomics unravels denitrification pathways. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 951:175457. [PMID: 39137850 DOI: 10.1016/j.scitotenv.2024.175457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2024] [Revised: 07/30/2024] [Accepted: 08/10/2024] [Indexed: 08/15/2024]
Abstract
The efficient nitrogen removal from micro-polluted source water is an international challenge to be solved urgently. However, the inner denitrification mechanism of native aerobic denitrifying bacterial communities in response to carbon scarcity remains relatively unclear. Here, the bacterial community XT6, screened from an oligotrophic reservoir, exhibited aerobic denitrifying capacity under low-carbon environments. Up to 76.79-81.64 % of total organic carbon (TOC) and 51.48-67.60 % of NO3--N were removed by XT6 within 48 h at C/N ratios of 2.0-3.0. Additionally, the nitrogen balance experiments further manifested that 26.27-38.13 % of NO3--N was lost in gaseous form. As the C/N ratio decreased, XT6 tended to generate more extracellular polymeric substances (EPS), with the tightly bound EPS showing the largest increase. Pseudomonas and Variovorax were quite abundant in XT6, constituting 59.69 % and 28.65 % of the total sequences, respectively. Furthermore, metagenomics analysis evidenced that XT6 removed TOC and nitrate mainly through the tricarboxylic acid cycle and aerobic denitrification. Overall, the abovementioned results provide a deeper understanding of the nitrogen metabolic pathways of indigenous aerobic denitrifying bacterial communities with low C/N ratios and offer useful guidance for controlling nitrogen pollution in oligotrophic ecosystems.
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Affiliation(s)
- Liqing Kou
- Shaanxi Provincial Field Scientific Observation and Research Station of Water Quality in Qinling Mountains, Xi'an University of Architecture and Technology, Xi'an 710055, PR China; Collaborative Innovation Center of Water Pollution Control and Water Quality Security Assurance of Shaanxi Province, Xi'an University of Architecture and Technology, Xi'an 710055, PR China
| | - Tinglin Huang
- Shaanxi Provincial Field Scientific Observation and Research Station of Water Quality in Qinling Mountains, Xi'an University of Architecture and Technology, Xi'an 710055, PR China; Collaborative Innovation Center of Water Pollution Control and Water Quality Security Assurance of Shaanxi Province, Xi'an University of Architecture and Technology, Xi'an 710055, PR China.
| | - Haihan Zhang
- Shaanxi Provincial Field Scientific Observation and Research Station of Water Quality in Qinling Mountains, Xi'an University of Architecture and Technology, Xi'an 710055, PR China; Collaborative Innovation Center of Water Pollution Control and Water Quality Security Assurance of Shaanxi Province, Xi'an University of Architecture and Technology, Xi'an 710055, PR China
| | - Gang Wen
- Shaanxi Provincial Field Scientific Observation and Research Station of Water Quality in Qinling Mountains, Xi'an University of Architecture and Technology, Xi'an 710055, PR China; Collaborative Innovation Center of Water Pollution Control and Water Quality Security Assurance of Shaanxi Province, Xi'an University of Architecture and Technology, Xi'an 710055, PR China
| | - Kai Li
- Shaanxi Provincial Field Scientific Observation and Research Station of Water Quality in Qinling Mountains, Xi'an University of Architecture and Technology, Xi'an 710055, PR China; Collaborative Innovation Center of Water Pollution Control and Water Quality Security Assurance of Shaanxi Province, Xi'an University of Architecture and Technology, Xi'an 710055, PR China
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Bertrans-Tubau L, Martínez-Campos S, Lopez-Doval J, Abril M, Ponsá S, Salvadó V, Hidalgo M, Pico-Tomàs A, Balcazar JL, Proia L. Nature-based bioreactors: Tackling antibiotic resistance in urban wastewater treatment. ENVIRONMENTAL SCIENCE AND ECOTECHNOLOGY 2024; 22:100445. [PMID: 39055482 PMCID: PMC11269294 DOI: 10.1016/j.ese.2024.100445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 06/24/2024] [Accepted: 06/27/2024] [Indexed: 07/27/2024]
Abstract
The overuse and misuse of antibiotics have accelerated the selection of antibiotic-resistant bacteria, significantly impacting human, animal, and environmental health. As aquatic environments are vulnerable to antibiotic resistance, suitable management practices should be adopted to tackle this phenomenon. Here we show an effective, nature-based solution for reducing antibiotic resistance from actual wastewater. We utilize a bioreactor that relies on benthic (biofilms) and planktonic microbial communities to treat secondary effluent from a small urban wastewater treatment plant (<10,000 population equivalent). This treated effluent is eventually released into the local aquatic ecosystem. We observe high removal efficiency for genes that provide resistance to commonly used antibiotic families, as well as for mobile genetic elements that could potentially aid in their spread. Importantly, we notice a buildup of sulfonamide (sul1 and sul2) and tetracycline (tet(C), tet(G), and tetR) resistance genes specifically in biofilms. This advancement marks the initial step in considering this bioreactor as a nature-based, cost-effective tertiary treatment option for small UWWTPs facing antibiotic resistance challenges.
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Affiliation(s)
- Lluís Bertrans-Tubau
- BETA Technological Centre- University of Vic- Central University of Catalunya (BETA- UVIC- UCC), Carretera de Roda 70, 08500, Vic, Barcelona, Spain
| | - Sergio Martínez-Campos
- BETA Technological Centre- University of Vic- Central University of Catalunya (BETA- UVIC- UCC), Carretera de Roda 70, 08500, Vic, Barcelona, Spain
| | - Julio Lopez-Doval
- BETA Technological Centre- University of Vic- Central University of Catalunya (BETA- UVIC- UCC), Carretera de Roda 70, 08500, Vic, Barcelona, Spain
| | - Meritxell Abril
- BETA Technological Centre- University of Vic- Central University of Catalunya (BETA- UVIC- UCC), Carretera de Roda 70, 08500, Vic, Barcelona, Spain
| | - Sergio Ponsá
- BETA Technological Centre- University of Vic- Central University of Catalunya (BETA- UVIC- UCC), Carretera de Roda 70, 08500, Vic, Barcelona, Spain
| | - Victoria Salvadó
- Chemistry Department, University of Girona. Campus Montilivi, 17005, Girona, Spain
| | - Manuela Hidalgo
- Chemistry Department, University of Girona. Campus Montilivi, 17005, Girona, Spain
| | - Anna Pico-Tomàs
- Catalan Institute Water Research (ICRA-CERCA), Emili Grahit 101, 17003, Girona, Spain
| | - Jose Luis Balcazar
- Catalan Institute Water Research (ICRA-CERCA), Emili Grahit 101, 17003, Girona, Spain
- University of Girona, 17004, Girona, Spain
| | - Lorenzo Proia
- BETA Technological Centre- University of Vic- Central University of Catalunya (BETA- UVIC- UCC), Carretera de Roda 70, 08500, Vic, Barcelona, Spain
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Li X, Li Y, Wu J. Different in root exudates and rhizosphere microorganisms effect on nitrogen removal between three emergent aquatic plants in surface flow constructed wetlands. CHEMOSPHERE 2023; 337:139422. [PMID: 37422212 DOI: 10.1016/j.chemosphere.2023.139422] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Revised: 06/05/2023] [Accepted: 07/04/2023] [Indexed: 07/10/2023]
Abstract
Swine wastewater contains high concentration of nitrogen (N), causing pollution of surrounding water bodies. Constructed wetlands (CWs) are considered as an effective ecological treatment measure to remove nitrogen. Some emergent aquatic plants could tolerate high ammonia, and play a crucial part in CWs to treat high concentration N wastewater. However, the mechanism of root exudates and rhizosphere microorganisms of emergent plants on nitrogen removal is still unclear. Effects of organic and amino acids on rhizosphere N cycle microorganisms and environmental factors across three emergent plants were investigated in this study. The highest TN removal efficiency were 81.20% in surface flow constructed wetlands (SFCWs) plant with Pontederia cordata. The root exudation rates results showed that organic and amino acids were higher in 56 d than that in 0 d in SFCWs plants with Iris pseudacorus and P. cordata. The highest ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) gene copy numbers were found in I. pseudacorus rhizosphere soil, while the highest nirS, nirK, hzsB and 16S rRNA gene copy numbers were detected in P. cordata rhizosphere soil. Regression analysis results demonstrated that organic and amino acids exudation rates were positive related to rhizosphere microorganisms. These results indicated that organic and amino acids secretion could stimulate growth of emergent plants rhizosphere microorganisms in SFCWs for swine wastewater treatment. In addition, the EC, TN, NH4+-N and NO3--N were negatively correlated with organic and amino acids exudation rates, and abundances of rhizosphere microorganisms via Pearson correlation analysis. These results imply that organic and amino acids, and rhizosphere microorganisms synergically affected on the nitrogen removal in SFCWs.
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Affiliation(s)
- Xi Li
- Key Laboratory of Agro-ecological Processes in Subtropical Regions, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan, 410125, China; Changsha Research Station for Agricultural & Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan, 410125, China
| | - Yuyuan Li
- Key Laboratory of Agro-ecological Processes in Subtropical Regions, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan, 410125, China; Changsha Research Station for Agricultural & Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan, 410125, China.
| | - Jinshui Wu
- Key Laboratory of Agro-ecological Processes in Subtropical Regions, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan, 410125, China; Changsha Research Station for Agricultural & Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan, 410125, China; University of Chinese Academy of Sciences, Beijing 100049, China
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Long Y, Ma Y, Wan J, Wang Y, Tang M, Fu H, Cao J. Denitrification efficiency, microbial communities and metabolic mechanisms of corn cob hydrolysate as denitrifying carbon source. ENVIRONMENTAL RESEARCH 2023; 221:115315. [PMID: 36657591 DOI: 10.1016/j.envres.2023.115315] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 01/11/2023] [Accepted: 01/14/2023] [Indexed: 06/17/2023]
Abstract
In this study, the denitrification efficacy of corn cob hydrolysate (CCH) was compared and analyzed with that of glucose and acetate to determine its feasibility as an additional carbon source, and its metabolic mechanism as a denitrification carbon source was investigated in depth. By constructing a denitrification reactor, it was found that the TN removal rate exceeded 97% and the effluent COD remained below 70 mg/L during the stable operation with CCH as the carbon source, and the denitrification effect was comparable to that of the glucose stage (GS) and the acetate stage (AS). The analysis of the microbial community showed that the dominant phylum was Proteobacteria and Bacteroidota, where the abundance of Bacteroidota in the hydrolysate stage (HS) (24.37%) was significantly higher than that of GS (4.89%) and AS (11.93%). And the analysis at the genus level showed the presence of a large number of genera of organic matter hydrolysis and acid production in HS that were almost absent in other stages, such as Paludibacter (12.83%), Gracilibacteria (4.27%), f__Prolixibacteraceae_Unclassified (2.94%). In addition, the higher fatty acid metabolism and lower sugar metabolism of HS during carbon metabolism were similar to the ratio of AS, suggesting that CCH was mainly fermented to acids and then involved in the tricarboxylic acid (TCA) cycle. During nitrogen metabolism, the high relative abundance of narG, nirS, and nosZ ensured the denitrification process. The results of this study were expected to provide a theoretical basis and data support for promoting denitrification from novel carbon sources.
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Affiliation(s)
- Yingping Long
- College of Environment and Energy, South China University of Technology, Guangzhou, 510006, China
| | - Yongwen Ma
- College of Environment and Energy, South China University of Technology, Guangzhou, 510006, China; Guangdong Plant Fiber High-Valued Cleaning Utilization Engineering Technology Research Center, Guangzhou, 510006, China.
| | - Jinquan Wan
- College of Environment and Energy, South China University of Technology, Guangzhou, 510006, China; Guangdong Plant Fiber High-Valued Cleaning Utilization Engineering Technology Research Center, Guangzhou, 510006, China
| | - Yan Wang
- College of Environment and Energy, South China University of Technology, Guangzhou, 510006, China; Guangdong Plant Fiber High-Valued Cleaning Utilization Engineering Technology Research Center, Guangzhou, 510006, China
| | - Min Tang
- College of Environment and Energy, South China University of Technology, Guangzhou, 510006, China
| | - Hao Fu
- College of Environment and Energy, South China University of Technology, Guangzhou, 510006, China
| | - Jianye Cao
- College of Environment and Energy, South China University of Technology, Guangzhou, 510006, China
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Shi J, Zhang G, Zhang S, Lu R, Chen M. Biodegradation and optimization of bilge water in a sequencing batch reactor using response surface methodology. CHEMOSPHERE 2022; 307:135654. [PMID: 35863410 DOI: 10.1016/j.chemosphere.2022.135654] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 06/23/2022] [Accepted: 07/05/2022] [Indexed: 06/15/2023]
Abstract
Bilge water is a significant source of pollution in the marine environment and has captured widespread international attention. In this study, a sequencing batch reactor (SBR) combined with strain S2 identified as Bacillus licheniformis was employed to assess the biodegradation of Chemical Oxygen Demand (COD) from bilge water. The influencing variables such as temperature, pH level and inoculum concentration on the performance SBR system were optimized by utilizing response surface methodology (RSM). The experimental results showed that the maximum COD removal of 77.81% was reached at the optimal SBR operation conditions of temperature 35.44 °C pH 8.13, and inoculum concentration 31.47 mL. In the practical application of SBR, it was found that the decrease in hydraulic retention time (HRT) was accompanied by a decrease in COD degradation rate. The biodegradation kinetics of COD in bilge water were well fitted with the first-order equation with a higher R2 value of 0.98106. In conclusion, COD in bilge water can be efficiently biodegraded by SBR under the optimization of RSM.
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Affiliation(s)
- Jianqiang Shi
- College of Merchant Marine, Shanghai Maritime University, Shanghai, 201306, China.
| | - Guichen Zhang
- College of Merchant Marine, Shanghai Maritime University, Shanghai, 201306, China
| | - Shaojun Zhang
- School of Navigation and Shipping, Shandong Jiaotong University, Weihai, 264200, China
| | - Run Lu
- College of Merchant Marine, Shanghai Maritime University, Shanghai, 201306, China
| | - Mengwei Chen
- College of Merchant Marine, Shanghai Maritime University, Shanghai, 201306, China
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He Y, Zhang Y, Li T, Peng X, Jia X. High-concentration COD wastewater treatment with simultaneous removal of nitrogen and phosphorus by a novel Candida tropicalis strain: Removal capability and mechanism. ENVIRONMENTAL RESEARCH 2022; 212:113471. [PMID: 35613633 DOI: 10.1016/j.envres.2022.113471] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Revised: 04/25/2022] [Accepted: 05/10/2022] [Indexed: 06/15/2023]
Abstract
Aerobic and anaerobic continuous stirred-tank reactor (CSTR), up-flow anaerobic sludge blanket (UASB) were set up and inoculated with newly isolated Candida tropicalis. Reactors were operated at high concentrations of chemical oxygen demand (COD) (8000 mg/L), the modified UASB expressed better COD removal rate simultaneously removal of nitrogen and phosphate than other two reactors. Notably, under both aerobic or anaerobic conditions, large amounts of organic acids and alcohol were generated. Transcriptomic analysis showed that carbon metabolism under anaerobic conditions shared the same pathway with aerobic conditions by regulating and inhibiting some functional genes. Experiments utilizing different carbon sources proved that our strain has excellent performances in utilizing organic materials, which were verified by transcriptomic analysis. Finally, the strain was applied to treat four types of sugar-containing wastewaters. Among them, our strain exerts the best removal capability of COD (90%), nitrogen (89%), and phosphate (82%) for brewery wastewater.
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Affiliation(s)
- Yuzhe He
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510006, China
| | - Yaqi Zhang
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510006, China
| | - Tianyu Li
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510006, China
| | - Xingxing Peng
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510006, China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou, 510275, China.
| | - Xiaoshan Jia
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510006, China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou, 510275, China.
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A Study of a Composite Biofilm Reactor for the Treatment of Mariculture Wastewater: Performance and Microbial Communities. SUSTAINABILITY 2022. [DOI: 10.3390/su14105743] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Mariculture wastewater is one of the main sources of saline wastewater. This study used a waterfall aeration biofilm reactor combined with a sequencing batch reactor (WABR-SBR) to treat simulated mariculture sewage. Despite the high inhibition by salinity, the reactor maintained a high removal efficiency for organic matter and ammonium nitrogen. The ammonia nitrogen removal rate was greater than 99%, while that for nitrite, which is extremely toxic to farmed animals, was greater than 80%. Fourier transform infrared spectroscopy and scanning electron microscopy showed that salinity affected the surface structure and composition of biofilms, which became compact and secreted more solute to resist the impact of salinity. High throughput 16S rRNA sequencing revealed that the main phyla in the biofilms were Actinobacteria, Proteobacteria, Firmicutes, and Bacteroidetes. Metagenomic annotation of genes further indicated nitrogen metabolism pathways under high salinity. The conclusions of this study can provide a theoretical foundation for the biological treatment of high-salt wastewater and provide a technical reference for further application of the WABR-SBR composite system.
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