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Benekos AK, Vasiliadou IA, Tekerlekopoulou AG, Alexandropoulou M, Pavlou S, Katsaounis A, Vayenas DV. Groundwater denitrification using a continuous flow mode hybrid system combining a hydrogenotrophic biofilter and an electrooxidation cell. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2023; 339:117914. [PMID: 37086640 DOI: 10.1016/j.jenvman.2023.117914] [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: 11/30/2022] [Revised: 03/30/2023] [Accepted: 04/09/2023] [Indexed: 05/03/2023]
Abstract
An attached-growth continuous flow hydrogenotrophic denitrification system was investigated for groundwater treatment. Two bench-scale packed-bed reactors were used in series, without external pH adjustment or carbon source addition, while inorganic carbonate salts already contained in the groundwater were the sole carbon source used by the denitrifying bacteria. The hydrogen was produced by water electrolysis using renewable energy sources thus minimizing resource-draining factors of the treatment process. The biofilter was subjected to a combination of three groundwater retention times (13.5, 27 and 54 min, corresponding to 20, 10 and 5 mL min-1 inlet water flow rates) and two hydrogen flow values (10 and 20 mL min-1) to evaluate its efficiency under different operating parameters. In all cases, significant nitrate percentage removals were achieved, ranged between 64.1% and 100%. The treatment process appears to slow down with lower retention times and H2 flow rate values, although residual nitrate concentrations were always in the range of 0-5.1 mg L-1, values below the maximum permitted limit of 11.3 mg L-1. In cases where nitrite accumulation was detected, a continuous flow electrochemical oxidation process with three different current density values (5.0, 7.5 and 10.0 mA cm-2) was examined as a post-treatment step aiming to completely remove the toxic nitrite anions. Finally, an advanced mathematical model of the attached growth hydrogenotrophic denitrification process was developed to predict concentrations of all the substrates examined in the bio-filter (nitrate, nitrite, inorganic carbon and hydrogen).
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Affiliation(s)
- Andreas K Benekos
- Department of Chemical Engineering, University of Patras, Rio, GR-26504, Patras, Greece
| | - Ioanna A Vasiliadou
- Department of Civil Engineering, Democritus University of Thrace, GR-67100, Xanthi, Greece.
| | | | - Maria Alexandropoulou
- Institute of Chemical Engineering Sciences (ICE-HT), Stadiou Str., Platani, GR-26504 Patras, Greece
| | - Stavros Pavlou
- Department of Chemical Engineering, University of Patras, Rio, GR-26504, Patras, Greece; Institute of Chemical Engineering Sciences (ICE-HT), Stadiou Str., Platani, GR-26504 Patras, Greece
| | - Alexandros Katsaounis
- Department of Chemical Engineering, University of Patras, Rio, GR-26504, Patras, Greece
| | - Dimitris V Vayenas
- Department of Chemical Engineering, University of Patras, Rio, GR-26504, Patras, Greece; Institute of Chemical Engineering Sciences (ICE-HT), Stadiou Str., Platani, GR-26504 Patras, Greece
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Cao L, Ge R, Xu W, Zhang Y, Li G, Xia X, Zhang F. Simultaneous removal of nitrate, nitrobenzene and aniline from groundwater in a vertical baffled biofilm reactor. CHEMOSPHERE 2022; 309:136746. [PMID: 36209853 DOI: 10.1016/j.chemosphere.2022.136746] [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: 06/09/2022] [Revised: 09/30/2022] [Accepted: 10/01/2022] [Indexed: 06/16/2023]
Abstract
The challenge of simultaneous removal of nitrobenzene (NB), aniline (AN) and nitrate from groundwater in a single bioreactor is mainly attributed to the persistence of AN to degradation with anoxic denitrification conditions. In this work, simultaneous removal of NB (100 μM), AN (100 μM) and nitrate (1 mM) was achieved within 8 h with a COD/N ratio of 8 in a vertical baffled biofilm reactor (VBBR). By setting DO concentration at 0.4-0.5 mg L-1 to create a micro-aerobic condition, NB removal rate was accelerated without accumulation of AN, and AN could serve as electron donors for denitrification after ring cleavage. High-throughput sequencing showed that biofilm was predominated by denitrifiers (Luteimonas, Planctomyces, Thiobacillus, Thauera and so on) and NB-degrading bacteria (Pseudomonas), and biodiversity varied vertically along the height of the reactor. A dominantly anaerobic pathway for reducing NB to AN was identified by PICRUSt analysis, as the predicted genes involved in aerobic transformation of NB were several magnitudes lower than those in the anaerobic pathway. This study provided a new insight to the role of oxygen in robust bioremediation groundwater contaminated with NB, AN and nitrate.
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Affiliation(s)
- Lifeng Cao
- State Key Joint Laboratory of Environment Simulation and Pollution Control, State Environment Protection Key Laboratory of Microorganism Application and Risk Control, School of Environment, Tsinghua University, Beijing, 100084, PR China; National Engineering Laboratory for Site Remediation Technologies (NEL-SRT), Beijing, 100015, PR China
| | - Runlei Ge
- State Key Joint Laboratory of Environment Simulation and Pollution Control, State Environment Protection Key Laboratory of Microorganism Application and Risk Control, School of Environment, Tsinghua University, Beijing, 100084, PR China
| | - Wenxin Xu
- State Key Joint Laboratory of Environment Simulation and Pollution Control, State Environment Protection Key Laboratory of Microorganism Application and Risk Control, School of Environment, Tsinghua University, Beijing, 100084, PR China
| | - Yongming Zhang
- Department of Environmental Science and Engineering, School of Environmental and Geographical Science, Shanghai Normal University, Shanghai, 200234, China
| | - Guanghe Li
- State Key Joint Laboratory of Environment Simulation and Pollution Control, State Environment Protection Key Laboratory of Microorganism Application and Risk Control, School of Environment, Tsinghua University, Beijing, 100084, PR China; National Engineering Laboratory for Site Remediation Technologies (NEL-SRT), Beijing, 100015, PR China
| | - Xue Xia
- College of Life and Environmental Sciences, Minzu University of China, Beijing, 100081, China.
| | - Fang Zhang
- State Key Joint Laboratory of Environment Simulation and Pollution Control, State Environment Protection Key Laboratory of Microorganism Application and Risk Control, School of Environment, Tsinghua University, Beijing, 100084, PR China; National Engineering Laboratory for Site Remediation Technologies (NEL-SRT), Beijing, 100015, PR China.
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Development of Bio-Electrochemical Reactor for Groundwater Denitrification: Effect of Electric Current and Water Hardness. SUSTAINABILITY 2022. [DOI: 10.3390/su14159454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Nitrate-nitrogen (NO3-N) contaminating groundwater is an environmental issue in many areas, and is difficult to treat by simple processes. A bio-electrochemical reactor (BER) using copper wire and graphite plate was developed to purify the NO3-N-contaminated groundwater. The low (of 10 mA) and high (of 20 mA) electric currents were applied to the BERs, and various influent hardness levels from 20 to 80 mg/L as CaCO3 due to groundwater characteristics were supplied to clarify the total nitrogen removal efficiency and NO3-N removal mechanisms. In the BER-10, the bio-electrochemical reactions caused 85% of total nitrogen to be removed through heterotrophic and autohydrogenotrophic denitrification in the suspended sludge and biofilm. However, the chemical deposit occurring at the cathode from water hardness affected the decreasing denitrification performance; 12.6% of Mg and 8.8% of Ca elements were observed in the biofilm. The enhancement of electrochemical reactions in the BER-20 caused integrating electrochemical and bio-electrochemical reactions; the NO3-N was electrochemically reduced to NO2-N, and it was further biologically reduced to N2. A better total nitrogen removal of 95% was found; although, a larger deposit of Mg (22.8%) and Ca (10.8%) was observed. The relatively low dissolved H2 in the BER-20 confirmed that the deposit affected the decreasing gaseous H2 transfer and inhibition of autohydrogenotrophic denitrification in the suspended sludge. According to the microbial analysis, both heterotrophic and autohydrogenotrophic denitrification were obtained in the suspended sludge of both BERs; Nocadia (26.8%) was the most abundant genus in the BER-10, whereas Flavobacterium (27.1%) and Nocadia (25.0%) were the dominant genera in the BER-20.
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Zhao B, Sun Z, Liu Y. An overview of in-situ remediation for nitrate in groundwater. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 804:149981. [PMID: 34517309 DOI: 10.1016/j.scitotenv.2021.149981] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 08/19/2021] [Accepted: 08/24/2021] [Indexed: 06/13/2023]
Abstract
Faced with the increasing nitrate pollution in groundwater, in-situ remediation has been widely studied and applied on field-scale as an efficient, economical and less disturbing remediation technology. In this review, we discussed various in-situ remediation for nitrate in groundwater and elaborate on biostimulation, phytoremediation, electrokinetic remediation, permeable reactive barrier and combined remediation. This review described principles of each in-situ remediation, application, the latest progress, problems and challenges on field-scale. Factors affecting the efficiency of in-situ remediation for nitrate in groundwater are also summarized. Finally, this review presented the prospect of in-situ remediation for nitrate pollution in groundwater. The objective of this review is to examine the state of knowledge on in-situ remediation for nitrate in groundwater and critically evaluate factors which affect the up-scaling of laboratory and bench-scale research to field-scale application. This helps to better understand the control mechanisms of various in-situ remediation for nitrate pollution in groundwater and the design options available for application to the field-scale.
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Affiliation(s)
- Bei Zhao
- China University of Geosciences (Beijing), Beijing 100083, China
| | - Zhanxue Sun
- State Key Laboratory of Nuclear Resources and Environment, East China University of Technology, Nanchang 330013, China.
| | - Yajie Liu
- State Key Laboratory of Nuclear Resources and Environment, East China University of Technology, Nanchang 330013, China
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