1
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Han X, Liu J, Zhu Z, Lin Y, Peng Y. Strengthening the enrichment of anaerobic ammonia oxidizing bacteria in biofilms through sludge concentration control. ENVIRONMENTAL RESEARCH 2024; 262:119784. [PMID: 39142456 DOI: 10.1016/j.envres.2024.119784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2024] [Revised: 07/26/2024] [Accepted: 08/11/2024] [Indexed: 08/16/2024]
Abstract
Controlling sludge concentration is an effective means to achieve PN. In this article, the reactor used domestic sewage as raw water and promoted the high enrichment of anammox bacteria by controlling the MLVSS of flocs to 1000-1500 mg/L and increasing the concentration of filler sludge. The measures to reduce the concentration of flocculent sludge increased the proliferation rate of the biofilm and provided sufficient substrate for AnAOB. After 102 days of operation, the abundance of Candidatus Brocadia increased from 0.43% during inoculation to 23.56% in phase VI. The ability of the microbial community to utilize energy metabolism and produce ATP was significantly improved, and the appropriate distribution of anammox bacteria and nitrifying, denitrifying bacteria in the ecological niche led to its high enrichment. In summary, this study proposes a strategy to promote the high enrichment of anammox bacteria in mainstream domestic sewage without adding any chemicals.
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Affiliation(s)
- Xueke Han
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing, 100124, PR China
| | - Jinjin Liu
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing, 100124, PR China
| | - Zhuo Zhu
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing, 100124, PR China
| | - Yangang Lin
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing, 100124, PR China
| | - Yongzhen Peng
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing, 100124, PR China.
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2
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Wang L, Zhao Q, Zhang L, Wu D, Zhou J, Peng Y. S 0-driven partial denitrification coupled with anammox (S 0PDA) enables highly efficient autotrophic nitrogen removal from wastewater. WATER RESEARCH 2024; 255:121418. [PMID: 38492314 DOI: 10.1016/j.watres.2024.121418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2023] [Revised: 03/01/2024] [Accepted: 03/04/2024] [Indexed: 03/18/2024]
Abstract
This study proposed a novel strategy that integrates S0 particles (diameter: 2-3 mm) and granular sludge to establish S0-driven partial denitrification coupled with anammox (S0PDA) process for autotrophic nitrogen removal from NH4+- and NO3--containing wastewaters. This process was evaluated using an up-flow anoxic sludge bed bioreactor, operating continuously for 240 days. The influent concentrations of NH4+ and NO3- were 29.9 ± 2.7 and 50.2 ± 2.7 mg-N/L, respectively. Throughout the operation, the hydraulic retention time was shortened from 4.0 h to 2.0 h, while the effluent concentrations of NH4+ and NO3- were maintained at a desirable level of 1.45-1.51 mg-N/L and 4.46-6.52 mg-N/L, respectively. Despite an autotrophic process, the nitrogen removal efficiency and rate reached up to 88.5 ± 2.0 % and 1.75 ± 0.07 kg-N/(m3·d), respectively, indicating the remarkable robustness of the S0PDA process. Autotrophic anammox and sulfur-oxidizing bacteria (Candidatus Brocadia and Thiobacillus) were the predominant bacterial genera involved in the S0PDA process. Candidatus Brocadia was primarily enriched in the granular sludge, with a relative abundance of 6.70 %. Thiobacillus occupied a unique niche on the S0 particles, with a relative abundance as high as 57.6 %, of which Thiobacillus thioparus with partial denitrification function (reducing NO3- to NO2- without further reduction to N2) accounted for 78.0 %. These findings challenge the stereotype of low efficiency in autotrophic nitrogen removal from wastewater, shedding fresh light on the applications of autotrophic processes.
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Affiliation(s)
- Luyao Wang
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Qi Zhao
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Liang Zhang
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Di Wu
- Qingdao SPRING Water Treatment Co.Ltd., Qingdao 266510, PR China
| | - Jiazhong Zhou
- Qingdao SPRING Water Treatment Co.Ltd., Qingdao 266510, PR China
| | - Yongzhen Peng
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China.
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3
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Xie Y, Zhang Q, Wu Q, Zhang J, Dzakpasu M, Wang XC. Novel adaptive activated sludge process leverages flow fluctuations for simultaneous nitrification and denitrification in rural sewage treatment. WATER RESEARCH 2024; 255:121535. [PMID: 38564890 DOI: 10.1016/j.watres.2024.121535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2024] [Revised: 03/24/2024] [Accepted: 03/26/2024] [Indexed: 04/04/2024]
Abstract
The fluctuating characteristics of rural sewage flow pose a significant challenge for wastewater treatment plants, leading to poor effluent quality. This study establishes a novel adaptive activated sludge (AAS) process specifically designed to address this challenge. By dynamically adjusting to fluctuating water flow in situ, the AAS maintains system stability and promotes efficient pollutant removal. The core strategy of AAS leverages the inherent dissolved oxygen (DO) variations caused by flow fluctuations to establish an alternating anoxic-aerobic environment within the system. This alternating operation mode fosters the growth of aerobic denitrifiers, enabling the simultaneous nitrification and denitrification (SND) process. Over a 284-day operational period, the AAS achieved consistently high removal efficiencies, reaching 94 % for COD and 62.8 % for TN. Metagenomics sequencing revealed HN-AD bacteria as the dominant population, with the characteristic nap gene exhibiting a high relative abundance of 0.008 %, 0.010 %, 0.014 %, and 0.015 % in the anaerobic, anoxic, dynamic, and oxic zones, respectively. Overall, the AAS process demonstrates efficient pollutant removal and low-carbon treatment of rural sewage by transforming the disadvantage of flow fluctuation into an advantage for robust DO regulation. Thus, AAS offers a promising model for SND in rural sewage treatment.
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Affiliation(s)
- Yadong Xie
- Key Lab of Northwest Water Resource, Environment, and Ecology, Ministry of Education, Xi'an University of Architecture and Technology, Xi'an, 710055 China
| | - Qionghua Zhang
- Key Lab of Northwest Water Resource, Environment, and Ecology, Ministry of Education, Xi'an University of Architecture and Technology, Xi'an, 710055 China; International Science & Technology Cooperation Center for Urban Alternative Water Resources Development, Xi'an, 710055 China.
| | - Qi Wu
- Key Lab of Northwest Water Resource, Environment, and Ecology, Ministry of Education, Xi'an University of Architecture and Technology, Xi'an, 710055 China
| | - Jiyu Zhang
- Key Lab of Northwest Water Resource, Environment, and Ecology, Ministry of Education, Xi'an University of Architecture and Technology, Xi'an, 710055 China
| | - Mawuli Dzakpasu
- International Science & Technology Cooperation Center for Urban Alternative Water Resources Development, Xi'an, 710055 China; School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China
| | - Xiaochang C Wang
- Key Lab of Northwest Water Resource, Environment, and Ecology, Ministry of Education, Xi'an University of Architecture and Technology, Xi'an, 710055 China; International Science & Technology Cooperation Center for Urban Alternative Water Resources Development, Xi'an, 710055 China
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4
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Cheng S, Li H, He X, Chen H, Li L. Improving anammox activity and reactor start-up speed by using CO 2/NaHCO 3 buffer. J Environ Sci (China) 2024; 139:60-71. [PMID: 38105078 DOI: 10.1016/j.jes.2023.05.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 04/28/2023] [Accepted: 05/12/2023] [Indexed: 12/19/2023]
Abstract
Anammox bacteria grow slowly and can be affected by large pH fluctuations. Using suitable buffers could make the start-up of anammox reactors easy and rapid. In this study, the effects of three kinds of buffers on the nitrogen removal and growth characteristics of anammox sludge were investigated. Reactors with CO2/NaHCO3 buffer solution (CCBS) performed the best in nitrogen removal, while 4-(2-hydroxyerhyl)piperazine-1-ethanesulfonic acid (HEPES) and phosphate buffer solution (PBS) inhibited the anammox activity. Reactors with 50 mmol/L CCBS could start up in 20 days, showing the specific anammox activity and anammox activity of 1.01±0.10 gN/(gVSS·day) and 0.83±0.06 kgN/(m3·day), respectively. Candidatus Kuenenia was the dominant anammox bacteria, with a relative abundance of 71.8%. Notably, anammox reactors could also start quickly by using 50 mmol/L CCBS under non-strict anaerobic conditions. These findings are meaningful for the quick start-up of engineered anammox reactors and prompt enrichment of anammox bacteria.
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Affiliation(s)
- Shaoan Cheng
- State Key Laboratory of Clean Energy Utilization, College of Energy Engineering, Zhejiang University, Hangzhou 310027, China.
| | - Huahua Li
- State Key Laboratory of Clean Energy Utilization, College of Energy Engineering, Zhejiang University, Hangzhou 310027, China
| | - Xinyuan He
- State Key Laboratory of Clean Energy Utilization, College of Energy Engineering, Zhejiang University, Hangzhou 310027, China
| | - Hua Chen
- State Key Laboratory of Clean Energy Utilization, College of Energy Engineering, Zhejiang University, Hangzhou 310027, China
| | - Longxin Li
- State Key Laboratory of Clean Energy Utilization, College of Energy Engineering, Zhejiang University, Hangzhou 310027, China
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5
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Zhao Q, Li X, Zhang L, Li J, Jia T, Zhao Y, Wang L, Peng Y. Partial denitrifying phosphorus removal coupling with anammox (PDPRA) enables synergistic removal of C, N, and P nutrients from municipal wastewater: A year-round pilot-scale evaluation. WATER RESEARCH 2024; 253:121321. [PMID: 38367384 DOI: 10.1016/j.watres.2024.121321] [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: 10/25/2023] [Revised: 01/11/2024] [Accepted: 02/14/2024] [Indexed: 02/19/2024]
Abstract
Applying anaerobic ammonium oxidation (anammox) in municipal wastewater treatment plants (MWWTPs) can unlock significant energy and resource savings. However, its practical implementation encounters significant challenges, particularly due to its limited compatibility with carbon and phosphorus removal processes. This study established a pilot-scale plant featuring a modified anaerobic-anoxic-oxic (A2O) process and operated continuously for 385 days, treating municipal wastewater of 50 m3/d. For the first time, we propose a novel concept of partial denitrifying phosphorus removal coupling with anammox (PDPRA), leveraging denitrifying phosphorus-accumulating organisms (DPAOs) as NO2- suppliers for anammox. 15N stable isotope tracing revealed that the PDPRA enabled an anammox reaction rate of 6.14 ± 0.18 μmol-N/(L·h), contributing 57.4 % to total inorganic nitrogen (TIN) removal. Metagenomic sequencing and 16S rRNA amplicon sequencing unveiled the co-existence and co-prosperity of anammox bacteria and DPAOs, with Candidatus Brocadia being highly enriched in the anoxic biofilms at a relative abundance of 2.46 ± 0.52 %. Finally, the PDPRA facilitated the synergistic conversion and removal of carbon, nitrogen, and phosphorus nutrients, achieving remarkable removal efficiencies of chemical oxygen demand (COD, 83.5 ± 5.3 %), NH4+ (99.8 ± 0.7 %), TIN (77.1 ± 3.6 %), and PO43- (99.3 ± 1.6 %), even under challenging operational conditions such as low temperature of 11.7 °C. The PDPRA offers a promising solution for reconciling the mainstream anammox and the carbon and phosphorus removal, shedding fresh light on the paradigm shift of MWWTPs in the near future.
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Affiliation(s)
- Qi Zhao
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Xiyao Li
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Liang Zhang
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Jianwei Li
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Tipei Jia
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Yang Zhao
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Luyao Wang
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Yongzhen Peng
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China.
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6
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Wang R, Liu J, Zhang Q, Li X, Wang S, Peng Y. Robustness of the anammox process at low temperatures and low dissolved oxygen for low C/N municipal wastewater treatment. WATER RESEARCH 2024; 252:121209. [PMID: 38309058 DOI: 10.1016/j.watres.2024.121209] [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: 09/12/2023] [Revised: 12/25/2023] [Accepted: 01/26/2024] [Indexed: 02/05/2024]
Abstract
Low water temperatures and ammonium concentrations pose challenges for anammox applications in the treatment of low C/N municipal wastewater. In this study, a 10 L-water bath sequencing batch reactor combing biofilm and suspended sludge was designed for low C/N municipal wastewater treatment. The nitrogen removal performance via partial nitrification anammox-(endogenous) denitrification anammox process was investigated with anaerobic-aerobic-anoxic mode at low temperatures and dissolved oxygen (DO). The results showed that with the decrease of temperature from 30 to 15℃, the influent and effluent nitrogen concentrations and nitrogen removal efficiencies were 73.7 ± 6.5 mg/L, 7.8 ± 2.8 mg/L, and 89.4 %, respectively, with aerobic hydraulic retention time of only 6 h and DO concentration of 0.2-0.5 mg/L. Among that, the stable anammox process compensated for the inhibitory effects of the low temperatures on the nitrification and denitrification processes. Notably, from 30 to 15℃, the anammox activity and relative abundance of the dominant Brocadia genus were increased from 39.7 to 45.5 mgN/gVSS/d and 7.3 to 12.0 %, respectively; the single gene expression level of the biofilm increased 9.0 times. The anammox bacteria showed a good adaptation to temperatures reduction. However, nitrogen removal by anammox was not improved by increasing DO (≥ 4 mg/L) at 8-4℃. Overall, the results of this study demonstrate the feasibility of the mainstream anammox process at low temperatures.
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Affiliation(s)
- Rui Wang
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Jinjin Liu
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Qiong Zhang
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Xiyao Li
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Shuying Wang
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Yongzhen Peng
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China.
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7
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Li B, Mao S, Zhang C, Xu T, Ma X, Lin H, Yin H, Qiu Y. Rapid anaerobic culture and reaction kinetic study of anammox bacteria on microfluidic chip. BIORESOURCE TECHNOLOGY 2024; 396:130422. [PMID: 38320714 DOI: 10.1016/j.biortech.2024.130422] [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: 12/09/2023] [Revised: 02/02/2024] [Accepted: 02/03/2024] [Indexed: 02/15/2024]
Abstract
Anammox bacteria are being increasingly investigated as part of an emerging nitrogen removal technology. However, due to the difficulty in culturing, current understanding of their behavior is limited. In this study, anaerobic microfluidic chips were used to study anammox bacteria, showing great advantages over reactors. On-chip fluorescence in situ hybridization (FISH) showed the relative abundance of free form anammox bacteria increased by 56.1 % after one week's culture, an increase that is three times higher than that of bioreactor (17.1 %). For granular form cultures, the nitrogen removal load reached 2.34 ∼ 2.51 kg-N/(m3·d), which was also substantially higher than the bioreactor (∼1.22 kg-N/(m3·d)). Furthermore, studying the kinetics of nitrite inhibition of granular sludge with different particle sizes (100-900 μm) showed that the maximum ammonia load and the nitrite semi-saturation coefficient noticeably decreased for smaller particle sizes. These results illustrate the usefulness of the microfluidic method for in-depth understanding anammox process and its implementation.
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Affiliation(s)
- Bing Li
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, China
| | - Siyuan Mao
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, China
| | - Chi Zhang
- School of Environment, Tsinghua University, Beijing 100084, China
| | - Tiansi Xu
- School of Environment, Tsinghua University, Beijing 100084, China
| | - Xueyan Ma
- School of Environment, Tsinghua University, Beijing 100084, China
| | - Hai Lin
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, China
| | - Huabing Yin
- James Watt School of Engineering, University of Glasgow, Glasgow G12 8LT, UK.
| | - Yong Qiu
- School of Environment, Tsinghua University, Beijing 100084, China.
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8
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Zhao Q, Zhang L, Li J, Jia T, Deng L, Liu Q, Sui J, Zhang Q, Peng Y. Carbon-Restricted Anoxic Zone as an Overlooked Anammox Hotspot in Municipal Wastewater Treatment Plants. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:21767-21778. [PMID: 38096549 DOI: 10.1021/acs.est.3c07017] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2023]
Abstract
The anoxic zone serves as the core functional unit in municipal wastewater treatment plants (MWWTPs). Unfortunately, in most cases, the downstream range of the anoxic zone is severely lacking in available organic carbon and thus contributes little to the removal of nutrients. This undesirable range is termed the "carbon-restricted anoxic zone", representing an insurmountable drawback for traditional MWWTPs. This study uncovers a previously overlooked role for the carbon-restricted anoxic zone: a hotspot for anaerobic ammonium oxidation (anammox). In a continuous-flow pilot-scale plant treating municipal wastewater (55 m3/d), virgin biocarriers were introduced into the carbon-restricted anoxic zone (downstream 25% of the anoxic zone with BOD5 of 5.9 ± 2.3 mg/L). During the 517-day monitoring, anammox bacteria highly self-enriched within the biofilms, with absolute and relative abundance reaching up to (9.4 ± 0.1) × 109 copies/g-VSS and 6.17% (Candidatus Brocadia), respectively. 15N isotopic tracing confirmed that anammox overwhelmingly dominated nitrogen metabolism, responsible for 92.5% of nitrogen removal. Following this upgrade, the contribution ratio of the carbon-restricted anoxic zone to total nitrogen removal increased from 9.2 ± 4.1% to 19.2 ± 4.2% (P < 0.001), while its N2O emission flux decreased by 84.5% (P < 0.001). These findings challenge stereotypes about the carbon-restricted anoxic zone and highlight the multiple environmental implications of this newfound anammox hotspot.
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Affiliation(s)
- Qi Zhao
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Liang Zhang
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Jianwei Li
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Tipei Jia
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Liyan Deng
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Qiyu Liu
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Jun Sui
- Guangdong Shouhui Lantian Engineering and Technology Co. Ltd, Guangdong 510075, PR China
| | - Qiong Zhang
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Yongzhen Peng
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
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9
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Han X, Zhang L, Yuan Y, Zhang Q, Peng Y. Anaerobic starvation realizes partial nitrification and starts anammox bacteria self-enrichment in mainstream municipal sewage treatment in a low filling ratio sequencing batch reactor. BIORESOURCE TECHNOLOGY 2023; 387:129505. [PMID: 37468012 DOI: 10.1016/j.biortech.2023.129505] [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: 06/09/2023] [Revised: 07/11/2023] [Accepted: 07/16/2023] [Indexed: 07/21/2023]
Abstract
The initiating and stable preservation of partial nitrification (PN) and achievement of anammox bacteria self-enrichment in domestic sewage is a purposeful subject. In this article, an originality tactics of anaerobic starvation for 100 days was adopted for rapidly achieving PN in actual wastewater, the nitrite accumulation rate (NAR) improved from 4.95% to 81.73% in 18 days. After anaerobic starvation was stopped, the stable PN effect furnished enough stroma for the growth of anammox bacteria. The abundance of Candidatus Brocadia grew from 0% to 0.42% in floc sludge and 0.43% in blank biofilm, which promoted nitrogen removal effect. Anaerobic starvation continuing 74 days generated further decrease in the abundance of Nitrobacter and Nitrospira of nitrite-oxidizing bacteria (NOB), indicating that anaerobic starvation can restore the destroyed partial nitrification. In conclusion, this article furnished a low-cost method for achieving anammox bacteria self-enrichment in mainstream municipal wastewater in 10% filling ratio without chemicals addition.
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Affiliation(s)
- Xueke Han
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, China
| | - Liyuan Zhang
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, China
| | - Yue Yuan
- Shanghai Municipal Engineering Design Institute (Group) Co., Ltd., Shanghai 200092, China
| | - Qiong Zhang
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, China
| | - Yongzhen Peng
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, China.
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10
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Su Y, Du R, Wang J, Li X, Zhang Q, Xue X, Peng Y. Pilot-scale demonstration of self-enrichment of anammox bacteria in a two-stage nitrification-denitrification suspended sludge system treating municipal wastewater under extremely low nitrogen loading rate. BIORESOURCE TECHNOLOGY 2023; 387:129693. [PMID: 37598806 DOI: 10.1016/j.biortech.2023.129693] [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: 07/15/2023] [Revised: 08/13/2023] [Accepted: 08/17/2023] [Indexed: 08/22/2023]
Abstract
In suspended sludge system, efficient enrichment and retention of anammox bacteria are crucial obstacles in mainstream wastewater treatment by anammox process. In this study, anammox bacteria was self-enriched in a pilot-scale suspended sludge system of two-stage nitrification-denitrification process serving municipal wastewater treatment. With the low ammonia (NH4+-N) of 9.3 mg/L, nitrate (NO3--N) of 15.6 mg/L and COD/NO3--N of 2.2 under extremely low nitrogen loading rate of 0.012 kg N/m3/d, anammox activity bloomed after its abundance increasing from 5.9 × 107 to 4.6 × 109 copies/g dry sludge. Significant NH4+-N removal was occurred and maintained stably in the denitrification reactor with anammox bacteria accounting for 1.13%, even under temperature decreasing to 20.0℃. The adequately anoxic environment, efficient retention with the static settlement, and NO2- production via NO3- reduction provided favorable environment for anammox bacteria. This study demonstrated the feasibility and great potential in mainstream anammox application without seeding specific sludge.
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Affiliation(s)
- Yunlong Su
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Rui Du
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China.
| | - Jiao Wang
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Xiyao Li
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Qiong Zhang
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Xiaofei Xue
- Beijing Enterprises Water Group (China) Investment Limited, Beijing 100102, PR China
| | - Yongzhen Peng
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
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11
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Wu T, Ding J, Zhong L, Sun HJ, Pang JW, Zhao L, Bai SW, Ren NQ, Yang SS. Sulfate-reducing ammonium oxidation: A promising novel process for nitrogen and sulfur removal. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 893:164997. [PMID: 37336410 DOI: 10.1016/j.scitotenv.2023.164997] [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: 02/08/2023] [Revised: 06/14/2023] [Accepted: 06/16/2023] [Indexed: 06/21/2023]
Abstract
Sulfate-reducing ammonium oxidation (sulfammox), a novel and promising process that has emerged in recent years, is essential to nitrogen and sulfur cycles and offers significant potential for the elimination of ammonium and sulfate. This review discussed the development of sulfammox process, the mechanism, characteristics of microbes, potential influencing factors, applicable bioreactors, and proposed the research needs and future perspective. The sulfammox process could be affected by many factors, such as the NH4+/SO42- ratio, carbon source, pH, and temperature. However, these potential influencing factors were only obtained based on what has been seen in papers studying related processes such as denitrification, sulfate-reduction, etc., and have to be further tested in bioreactors carrying out the sulfammox process in the future. Currently, sulfammox is predominantly used in granular activated carbon anaerobic fluidized beds, up-flow anaerobic sludge blanket reactors, anaerobic expanded granular bed reactors, rotating biological contact reactors, and moving bed biofilm reactors. In the future, the operating parameters of sulfammox should be further optimized to improve the processing performance, and the system can be further scaled up for actual wastewater treatment. In addition, the isolation, identification, and characterization of key functional microbes and the analysis of microbial interrelationships will also be focused on in future studies to enable an in-depth analysis of the sulfammox mechanism.
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Affiliation(s)
- Tong Wu
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China
| | - Jie Ding
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China
| | - Le Zhong
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China
| | - Han-Jun Sun
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China
| | - Ji-Wei Pang
- China Energy Conservation and Environmental Protection Group, CECEP Talroad Technology Co., Ltd., Beijing 100096, China
| | - Lei Zhao
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China
| | - Shun-Wen Bai
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China
| | - Nan-Qi Ren
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China
| | - Shan-Shan Yang
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China.
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Xu R, Cui H, Fan F, Zhang M, Yuan S, Wang D, Gan Z, Yu Z, Wang C, Meng F. Combination of Sequencing Batch Operation and A/O Process to Achieve Partial Mainstream Anammox: Pilot-Scale Demonstration and Microbial Ecological Mechanism. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:13887-13900. [PMID: 37667485 DOI: 10.1021/acs.est.3c03022] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/06/2023]
Abstract
In this study, sequencing batch operation was successfully combined with a pilot-scale anaerobic biofilm-modified anaerobic/aerobic membrane bioreactor to achieve anaerobic ammonium oxidation (anammox) without inoculation of anammox aggregates for municipal wastewater treatment. Both total nitrogen and phosphorus removal efficiencies of the reactor reached up to 80% in the 250-day operation, with effluent concentrations of 4.95 mg-N/L and 0.48 mg-P/L. In situ enrichment of anammox bacteria with a maximum relative abundance of 7.86% was observed in the anaerobic biofilm, contributing to 18.81% of nitrogen removal, with denitrification being the primary removal pathway (38.41%). Denitrifying phosphorus removal (DPR) (40.54%) and aerobic phosphorus uptake (48.40%) played comparable roles in phosphorus removal. Metagenomic sequencing results showed that the biofilm contained significantly lower abundances of NO-reducing functional genes than the bulk sludge (p < 0.01), favoring anammox catabolism in the former. Interactions between the anammox bacteria and flanking community were dominated by cooperation behaviors (e.g., nitrite supply, amino acids/vitamins exchange) in the anaerobic biofilm community network. Moreover, the hydrolytic/fermentative bacteria and endogenous heterotrophic bacteria (Dechloromonas, Candidatus competibacter) were substantially enriched under sequencing batch operation, which could alleviate the inhibition of anammox bacteria by complex organics. Overall, this study provides a feasible and promising strategy for substantially enriching anammox bacteria and achieving partial mainstream anammox as well as DPR.
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Affiliation(s)
- Ronghua Xu
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, P. R. China
- Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, P. R. China
| | - Hongcan Cui
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, P. R. China
- Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, P. R. China
| | - Fuqiang Fan
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, P. R. China
- Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, P. R. China
| | - Meng Zhang
- Department of Environmental Engineering, College of Environmental & Resource Sciences, Zhejiang University, Hangzhou 310058, P. R. China
| | - Shasha Yuan
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, P. R. China
- Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, P. R. China
| | - Depeng Wang
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, P. R. China
- Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, P. R. China
| | - Zhihao Gan
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, P. R. China
- Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, P. R. China
| | - Zhong Yu
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, P. R. China
- Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, P. R. China
| | - Chao Wang
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, P. R. China
- Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, P. R. China
| | - Fangang Meng
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, P. R. China
- Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, P. R. China
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13
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Fu Y, Xu R, Yang B, Wu Y, Xia L, Tawfik A, Meng F. Mediation of Bacterial Interactions via a Novel Membrane-Based Segregator to Enhance Biological Nitrogen Removal. Appl Environ Microbiol 2023; 89:e0070923. [PMID: 37404187 PMCID: PMC10370321 DOI: 10.1128/aem.00709-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 06/12/2023] [Indexed: 07/06/2023] Open
Abstract
The regulation of microbial subpopulations in wastewater treatment plants (WWTPs) with desired functions can guarantee nutrient removal. In nature, "good fences make good neighbors," which can be applied to engineering microbial consortia. Herein, a membrane-based segregator (MBSR) was proposed, where porous membranes not only promote the diffusion of metabolic products but also isolate incompatible microbes. The MBSR was integrated with an anoxic/aerobic membrane bioreactor (i.e., an experimental MBR). The long-term operation showed that the experimental MBR exhibited higher nitrogen removal (10.45 ± 2.73 mg/L total nitrogen) than the control MBR (21.68 ± 4.23 mg/L) in the effluent. The MBSR resulted in much lower oxygen reduction potential in the anoxic tank of the experimental MBR (-82.00 mV) compared to that of the control MBR (83.25 mV). The lower oxygen reduction potential can inevitably aid in the occurrence of denitrification. The 16S rRNA sequencing showed that the MBSR significantly enriched acidogenic consortia, which yielded considerable volatile fatty acids by fermenting the added carbon sources and allowed efficient transfer of these small molecules to the denitrifying community. Moreover, the sludge communities of the experimental MBR harbored a higher abundance of denitrifying bacteria than those of the control MBR. Metagenomic analysis further corroborated these sequencing results. The spatially structured microbial communities in the experimental MBR system demonstrate the practicability of the MBSR, achieving nitrogen removal efficiency superior to that of mixed populations. Our study provides an engineering method for modulating the assembly and metabolic division of labor of subpopulations in WWTPs. IMPORTANCE This study provides an innovative and applicable method for regulating subpopulations (activated sludge and acidogenic consortia), which contributes to the precise control of the metabolic division of labor in biological wastewater treatment processes.
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Affiliation(s)
- Yue Fu
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, PR China
- Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou, PR China
| | - Ronghua Xu
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, PR China
- Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou, PR China
| | - Boyi Yang
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, PR China
- Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou, PR China
| | - Yingxin Wu
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, PR China
- Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou, PR China
| | - Lichao Xia
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, PR China
- Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou, PR China
| | - Ahmed Tawfik
- National Research Centre, Water Pollution Research Department, Dokki, Cairo, Egypt
| | - Fangang Meng
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, PR China
- Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou, PR China
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14
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Zhao Q, Li J, Deng L, Jia T, Zhao Y, Li X, Peng Y. From hybrid process to pure biofilm anammox process: Suspended sludge biomass management contributing to high-level anammox enrichment in biofilms. WATER RESEARCH 2023; 236:119959. [PMID: 37058918 DOI: 10.1016/j.watres.2023.119959] [Citation(s) in RCA: 19] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2023] [Revised: 04/02/2023] [Accepted: 04/07/2023] [Indexed: 06/19/2023]
Abstract
The application of mainstream anammox is highly desirable for municipal wastewater treatment. However, enrichment of anammox bacteria (AnAOB) is challenging, particularly given the vicious competition from denitrifying bacteria (DB). Here, suspended sludge biomass management, a novel operational strategy for hybrid process (suspended sludge/biofilm), was investigated for 570 days based on a modified anaerobic-anoxic-oxic system treating municipal wastewater. By successively decreasing the suspended sludge concentration, the traditional hybrid process was successfully upgraded to a pure biofilm anammox process. During this process, both the nitrogen removal efficiency (NRE) and rate (NRR) were significantly improved (P < 0.001), from 62.1 ± 4.5% to 79.2 ± 3.9% and from 48.7 ± 9.7 to 62.3 ± 9.0 g N/(m3·d), respectively. Mainstream anammox was improved in the following: Candidatus Brocadia was enriched from 0.70% to 5.99% in anoxic biofilms [from (9.94 ± 0.99) × 108 to (1.16 ± 0.01) × 1010 copies/g VSS, P < 0.001]; the in situ anammox reaction rate increased from 8.8 ± 1.9 to 45.5 ± 3.2 g N/(m3·d) (P < 0.001); the anammox contribution to nitrogen removal rose from 9.2 ± 2.8% to 67.1 ± 8.3% (P < 0.001). Core bacterial microbiome analysis, functional gene quantification, and a series of ex situ batch experiments demonstrated that the stepwise decreases in suspended sludge concentration effectively mitigated the vicious competition of DB against AnAOB, enabling high-level AnAOB enrichment. This study presents a straightforward and effective strategy for enriching AnAOB in municipal wastewater, shedding fresh light on the application and upgradation of mainstream anammox.
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Affiliation(s)
- Qi Zhao
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Jianwei Li
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Liyan Deng
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Tipei Jia
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Yang Zhao
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Xiyao Li
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China
| | - Yongzhen Peng
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing 100124, PR China.
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15
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Zhang Q, Zheng J, Zhao L, Liu W, Chen L, Cai T, Ji XM. Succession of microbial communities reveals the inevitability of anammox core in the development of anammox processes. BIORESOURCE TECHNOLOGY 2023; 371:128645. [PMID: 36681349 DOI: 10.1016/j.biortech.2023.128645] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 01/09/2023] [Accepted: 01/15/2023] [Indexed: 06/17/2023]
Abstract
The lack of anammox seeds is regarded as the bottleneck of anammox-based processes. Although the interactions in anammox consortia have attracted increasing attention, little is known about the influence of inoculated sludge populations on the growth of anammox bacteria. In this study, four sludge of distinct communities mixed with anammox sludge (the relative abundance of Ca. Kuenenia was 1.96 %) were used as the seeds, respectively for the start-up of anammox processes. Notably, all these mixed microbial communities tend to form a similar microbial community, defined as the anammox core, containing anammox-bacteria (22.9 ± 5.9 %), ammonia-oxidizing-bacteria (0.8 ± 0.7 %), nitrite-oxidizing-bacteria (0.2 ± 0.2 %), Chloroflexi-bacteria (0.7 ± 0.4 %), and heterotrophic-denitrification-bacteria (0.3 ± 0.2 %). It also elucidated that the communities of Nitrosomonas-dominated sludge were the closest to the anammox core, and achieved the highest nitrogen-removal rate of 0.73 kg-N m-3 d-1. This study sheds light on the solution to the shortage of anammox seeds in the full-scale wastewater treatment application.
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Affiliation(s)
- Qi Zhang
- College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China
| | - Jinli Zheng
- College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China
| | - Leizhen Zhao
- College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China
| | - Wenru Liu
- School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou 215009, China
| | - Liwei Chen
- College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China
| | - Tianming Cai
- College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China
| | - Xiao-Ming Ji
- College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China.
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