1
|
Ipiales RP, Lelli G, Diaz E, Diaz-Portuondo E, Mohedano AF, de la Rubia MA. Study of two approaches for the process water management from hydrothermal carbonization of swine manure: Anaerobic treatment and nutrient recovery. ENVIRONMENTAL RESEARCH 2024; 246:118098. [PMID: 38184062 DOI: 10.1016/j.envres.2024.118098] [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: 10/30/2023] [Revised: 12/29/2023] [Accepted: 01/02/2024] [Indexed: 01/08/2024]
Abstract
Hydrothermal carbonization (HTC) is a promising alternative to transform biomass waste into a solid carbonaceous material (hydrochar) and a process water with potential for material and energy recovery. In this study, two alternatives for process water treatment by conventional and acid-assisted HTC of swine manure are discussed. Process water from conventional HTC at 180 °C showed high biodegradability (55% COD removal) and methane production (∼290 mL STP CH4 g-1 CODadded) and the treatment in an upflow anaerobic sludge blanket reactor allowed obtaining a high methane production yield (1.3 L CH4 L-1 d-1) and COD removal (∼70%). The analysis of the microbiota showed a high concentration of Synergistota and Firmicutes phyla, with high degradation of organic nitrogen-containing organic compounds. Acid-assisted HTC proved to be a viable option for nutrient recovery (migration of 83% of the P to the process water), which allowed obtaining a solid salt by chemical precipitation with Mg(OH)2 (NPK of 4/4/0.4) and MgCl2 (NPK 8/17/0.5), with a negligible content of heavy metals. The characteristics of the precipitated solid complied with the requirements of European Regulation (2019)/1009 for fertilizers and amendments in agricultural soils, being a suitable alternative for the recycling of nutrients from wastes.
Collapse
Affiliation(s)
- R P Ipiales
- Chemical Engineering Department, Universidad Autonoma de Madrid, 28049, Madrid, Spain; Arquimea Agrotech, 28400, Collado Villalba, Madrid, Spain
| | - G Lelli
- Chemical Engineering Department, Universidad Autonoma de Madrid, 28049, Madrid, Spain
| | - E Diaz
- Chemical Engineering Department, Universidad Autonoma de Madrid, 28049, Madrid, Spain
| | | | - A F Mohedano
- Chemical Engineering Department, Universidad Autonoma de Madrid, 28049, Madrid, Spain
| | - M A de la Rubia
- Chemical Engineering Department, Universidad Autonoma de Madrid, 28049, Madrid, Spain.
| |
Collapse
|
2
|
Thapa A, Park JH, Shin SG, Jo HM, Kim MS, Park Y, Han U, Cho SK. Elucidation of microbial interactions, dynamics, and keystone microbes in high pressure anaerobic digestion. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 858:159718. [PMID: 36302429 DOI: 10.1016/j.scitotenv.2022.159718] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 10/12/2022] [Accepted: 10/21/2022] [Indexed: 06/16/2023]
Abstract
High-pressure anaerobic digestion (HPAD) is a promising technology for producing biogas enriched with high methane content in a single-step process. To enhance HPAD performance, a comprehensive understanding of microbial community dynamics and their interactions is essential. For this, mesophilic batch high-pressurized anaerobic reactors were operated under 3 bars (H3) and 6 bars (H6). The experimental results showed that the effect of high-pressure (up to 6 bar) on acidification was negligible while methanogenesis was significantly delayed. Microbial analysis showed the predominance of Defluviitoga affiliated with the phylum Thermotogae and the reduction of Thiopseudomonas under high-pressure conditions. In addition, the microbial cluster pattern in H3 and H6 was significantly different compared to the CR, indicating a clear shift in microbial community structure. Moreover, Methanobacterium, Methanomicrobiaceae, Alkaliphilus, and Petrimonas were strongly correlated in network analysis, and they could be identified as keystone microbes in the HPAD reactor.
Collapse
Affiliation(s)
- Ajay Thapa
- Department of Biological and Environmental Science, Dongguk University, 32 Dongguk-ro, Ilsandong-gu, Goyang, Gyeonggi-do, Republic of Korea
| | - Jeong-Hoon Park
- Sustainable Technology and Wellness R&D Group, Korea Institute of Industrial Technology (KITECH), Jeju-si, Republic of Korea
| | - Seung Gu Shin
- Department of Energy System Engineering, Gyeongang National University, Gyeongnam 52725, Republic of Korea
| | - Hong-Mok Jo
- Department of Biological and Environmental Science, Dongguk University, 32 Dongguk-ro, Ilsandong-gu, Goyang, Gyeonggi-do, Republic of Korea
| | - Min-Sang Kim
- Department of Biological and Environmental Science, Dongguk University, 32 Dongguk-ro, Ilsandong-gu, Goyang, Gyeonggi-do, Republic of Korea
| | - Yeongmi Park
- Department of Biological and Environmental Science, Dongguk University, 32 Dongguk-ro, Ilsandong-gu, Goyang, Gyeonggi-do, Republic of Korea
| | - Uijeong Han
- Department of Biological and Environmental Science, Dongguk University, 32 Dongguk-ro, Ilsandong-gu, Goyang, Gyeonggi-do, Republic of Korea
| | - Si-Kyung Cho
- Department of Biological and Environmental Science, Dongguk University, 32 Dongguk-ro, Ilsandong-gu, Goyang, Gyeonggi-do, Republic of Korea.
| |
Collapse
|
3
|
Khan A, Khan SJ, Miran W, Zaman WQ, Aslam A, Shahzad HMA. Feasibility Study of Anaerobic Baffled Reactor Coupled with Anaerobic Filter Followed by Membrane Filtration for Wastewater Treatment. MEMBRANES 2023; 13:membranes13010079. [PMID: 36676886 PMCID: PMC9863547 DOI: 10.3390/membranes13010079] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2022] [Revised: 11/11/2022] [Accepted: 01/06/2023] [Indexed: 05/27/2023]
Abstract
The performance of a Decentralized Wastewater Treatment System (DWTS) comprising an Anaerobic Baffled Reactor (ABR) and an Anaerobic Filter (AF) and Membrane Filtration (MF) module was studied for domestic wastewater treatment. The efficiency of the system was evaluated by running ABR at four different HRTs (14, 12, 10, and 8 h) resulting in COD removal efficiencies of 74, 72, 69, and 65%, respectively. The performance of AF using four different filtration media, i.e., PVC pipe (25 mm), PVC pipe (20 mm), PVC pipe (15 mm), and Kaldnes K3, was determined at optimized HRT (12 h). Among all the filtration media tested, the highest performance efficiency of the system was found with the PVC pipe (20 mm), which showed COD, TP, and TKN removal of 79, 32, and 63%, respectively. The efficacy of the system was proven via significant COD and turbidity removal of 94.6 and 87.2%, respectively, by the combined system.
Collapse
Affiliation(s)
- Aamir Khan
- Institute of Environmental Sciences and Engineering, School of Civil and Environmental Engineering, National University of Sciences and Technology (NUST), Sector H-12, Islamabad 44000, Pakistan
| | - Sher Jamal Khan
- Institute of Environmental Sciences and Engineering, School of Civil and Environmental Engineering, National University of Sciences and Technology (NUST), Sector H-12, Islamabad 44000, Pakistan
| | - Waheed Miran
- School of Chemical and Materials Engineering, National University of Sciences and Technology (NUST), Sector H-12, Islamabad 44000, Pakistan
| | - Waqas Qamar Zaman
- Institute of Environmental Sciences and Engineering, School of Civil and Environmental Engineering, National University of Sciences and Technology (NUST), Sector H-12, Islamabad 44000, Pakistan
| | - Alia Aslam
- Institute of Environmental Sciences and Engineering, School of Civil and Environmental Engineering, National University of Sciences and Technology (NUST), Sector H-12, Islamabad 44000, Pakistan
| | - Hafiz Muhammad Aamir Shahzad
- Institute of Environmental Sciences and Engineering, School of Civil and Environmental Engineering, National University of Sciences and Technology (NUST), Sector H-12, Islamabad 44000, Pakistan
| |
Collapse
|
4
|
Mu S, Chen X, Song B, Wu C, Li Q. Enhanced performance and mechanism of the combined process of ozonation and a semiaerobic aged refuse biofilter for mature landfill leachate treatment. CHEMOSPHERE 2022; 308:136432. [PMID: 36115471 DOI: 10.1016/j.chemosphere.2022.136432] [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: 07/25/2022] [Revised: 09/01/2022] [Accepted: 09/09/2022] [Indexed: 06/15/2023]
Abstract
A semiaerobic aged refuse biofilter (SAARB) can effectively treat mature landfill leachate (ML), but prolonged operation can lead to the enrichment of pollutants in the biofilter, resulting in severely degraded treatment performance. In this study, we constructed a combination process of ozonation and a SAARB to treat ML based on the principles of selective oxidation of aromatic organics by ozone and the preference of microorganisms for ozonation products. The results showed that the removal of organic and nitrogen pollutants became extremely poor after long-term treatment of ML using the SAARB alone. The decrease of chemical oxygen demand (COD), light absorbance at 254 nm (UV254), NH4+, and total nitrogen (TN) improved significantly after recirculating the ozonated ML effluent (OLE) into the SAARB, and the removal extents increased significantly to 63.59% (COD), 26.14% (UV254), 92.85% (NH4+), and 52.04% (TN), respectively. In addition, the recirculation of OLE enhanced the complete denitrification and tolerance to high NH4+ loading by the SAARB. An analysis of the community composition of 16S_bacteria and ammonia oxidation bacteria (AOB) showed that long-term treatment of ML using the SAARB alone had difficulty enriching the dominant functional bacteria. In the OLE recirculation stage, environmental factors-such as influent organic matter species and concentration, nitrogen pollutant concentration, and pH-were changed to influence the community composition of 16S_bacteria and AOB and enrich functional bacteria (e.g., Truepera, Luteibacter, and Nitrosospira). Therefore, ozonation combined with a SAARB can remove organic and nitrogen pollutants more effectively. In particular, this can be used to solve the problem of inefficient total nitrogen removal using the SAARB alone. This study provides a theoretical reference for the efficient and stable operation of biological processes when treating ML.
Collapse
Affiliation(s)
- Shiqi Mu
- Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu 611756, China
| | - Xinglong Chen
- Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu 611756, China
| | - Bowen Song
- Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu 611756, China
| | - Chuanwei Wu
- Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu 611756, China
| | - Qibin Li
- Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu 611756, China.
| |
Collapse
|
5
|
Wang Y, Li W, Wang Y, Turap Y, Wang Z, Zhang Z, Xia Z, Wang W. Anaerobic co-digestion of food waste and sewage sludge in anaerobic sequencing batch reactors with application of co-hydrothermal pretreatment of sewage sludge and biogas residue. BIORESOURCE TECHNOLOGY 2022; 364:128006. [PMID: 36155815 DOI: 10.1016/j.biortech.2022.128006] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 09/16/2022] [Accepted: 09/17/2022] [Indexed: 06/16/2023]
Abstract
The effect of pretreatment technologies and reactor types on conversion efficiency and operating costs of anaerobic co-digestion of food waste and sewage sludge were investigated by 300-day continuous experiments. The volatile solids (VS) removal efficiency increased from 61% to 77% with the application of co-hydrothermal pretreatment of sewage sludge and biogas residue. Deep dewatering reduced the volume of hydrothermally pretreated biogas residue by 85%. When continuous stirred tank reactors (CSTRs) were converted to anaerobic sequencing batch reactors (ASBRs), vS removal efficiencies increased by 6%, attributed to a 1.4-1.6-fold increase in solids retention time (SRT). The bottom drainage of mineralized sludge every 40 days increased ASBR stability. Firmicutes and Methanosphaera dominated the bacterial and archaeal communities, respectively. Operating costs decreased by 14.9 US$/metric ton feedstock by applying ASBRs. Compared to CSTRs, ASBRs achieved higher organic matter conversion efficiency, smaller volume of biogas residue, and lower operating costs.
Collapse
Affiliation(s)
- Yidi Wang
- School of Environment, Tsinghua University, Beijing 100084, China
| | - Wei Li
- Beijing Da Bei Nong Technology Group Co., LTD, Beijing 100080, China
| | - Yongkang Wang
- School of Environment, Tsinghua University, Beijing 100084, China
| | - Yusan Turap
- School of Environment, Tsinghua University, Beijing 100084, China
| | - Zhentong Wang
- School of Environment, Tsinghua University, Beijing 100084, China
| | - Zhe Zhang
- School of Environment, Tsinghua University, Beijing 100084, China
| | - Zhou Xia
- School of Environment, Tsinghua University, Beijing 100084, China
| | - Wei Wang
- School of Environment, Tsinghua University, Beijing 100084, China.
| |
Collapse
|
6
|
Campbell BS, Thorpe RB, Peus D, Lee J. Anaerobic digestion of untreated and treated process water from the hydrothermal carbonisation of spent coffee grounds. CHEMOSPHERE 2022; 293:133529. [PMID: 34995617 DOI: 10.1016/j.chemosphere.2022.133529] [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: 10/04/2021] [Revised: 12/18/2021] [Accepted: 01/02/2022] [Indexed: 06/14/2023]
Abstract
This study investigates the long-term performance of the mesophilic (35 °C) anaerobic mono-digestion of process waters (PW) from the hydrothermal carbonisation (HTC) of spent coffee grounds. At an organic loading rate (OLR) of 0.4 gCOD L-1 d-1, initial instability was seen, but after 40 days and supplementary alkalinity, the digestion stabilised with the chemical oxygen demand (COD) in the untreated PW degraded with 37.8-64.6% efficiency and the yield of methane at 0.16 L gCOD-1. An increase in OLR to 0.8 gCOD L-1 d-1 caused a collapse in biogas production, and resulted in severe instability in the reactor, characterised by falling pH and an increasing volatile fatty acid concentration. Comparatively, the digestion of a treated PW (concentrated in nanofiltration and reverse osmosis after removal of the fouling fraction), at OLR between 0.4 and 0.8 gCOD L-1 d-1, was stable over the entire 117 days of treated PW addition, yielded methane at 0.21 L gCOD-1 and the COD was degraded with an average efficiency of 93.5% - the highest efficiency the authors have seen for HTC PW. Further anaerobic digestion of untreated PW at an average OLR of 0.95 gCOD L-1 d-1 was stable for 38 days, with an average COD degradation of 69.6%, and methane production between 0.15 and 0.19 L gCOD-1. The digestion of treated PW produced significantly higher COD degradation and methane yield than untreated PW, which is likely to be related to the removal of refractory and inhibitory organic material in the post-HTC treatment by adsorption of hydrophobic material.
Collapse
Affiliation(s)
- B S Campbell
- Department of Chemical and Process Engineering, University of Surrey, Guildford, GU2 7XH, UK
| | - R B Thorpe
- Department of Chemical and Process Engineering, University of Surrey, Guildford, GU2 7XH, UK
| | - D Peus
- Antaco UK Ltd (Antaco), Lantern House, Walnut Tree Close, Guildford, GU1 4SW, UK
| | - J Lee
- Department of Chemical and Process Engineering, University of Surrey, Guildford, GU2 7XH, UK.
| |
Collapse
|
7
|
Mannarino G, Sarrion A, Diaz E, Gori R, De la Rubia MA, Mohedano AF. Improved energy recovery from food waste through hydrothermal carbonization and anaerobic digestion. WASTE MANAGEMENT (NEW YORK, N.Y.) 2022; 142:9-18. [PMID: 35158176 DOI: 10.1016/j.wasman.2022.02.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 01/28/2022] [Accepted: 02/02/2022] [Indexed: 06/14/2023]
Abstract
Here we studied energy valorization of food waste by hydrothermal carbonization coupled with anaerobic digestion. Hydrothermal treatment was carried out at 200 °C and 230 °C for 1 h, obtaining hydrochar with properties suitable for solid biofuel according to ISO/TS 17225-8. The increase in temperature improved the fuel properties of hydrochar (higher heating value 20.3 and 23.7 MJ kg-1, fuel ratio 0.33 and 0.37, energy density 1.07 and 1.25). The anaerobic digestion of process water achieved methane yields around 150 mL CH4 STP g-1 CODadded and made it possible to remove some specific recalcitrant compounds, such as 2-methylpyridine and 2-ethyl-3-methylpyrazine. Energy recovery from hydrochar and process water seems to be an interesting alternative way to sustain the process energetically and economically, despite the significant energy inputs required for hydrothermal carbonization.
Collapse
Affiliation(s)
- Gemma Mannarino
- Department of Chemical Engineering, Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain; Department of Civil and Environmental Engineering, University of Florence, via di S. Marta 3, 50139 Florence, Italy.
| | - Andres Sarrion
- Department of Chemical Engineering, Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain
| | - Elena Diaz
- Department of Chemical Engineering, Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain
| | - Riccardo Gori
- Department of Civil and Environmental Engineering, University of Florence, via di S. Marta 3, 50139 Florence, Italy
| | - M Angeles De la Rubia
- Department of Chemical Engineering, Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain
| | - Angel F Mohedano
- Department of Chemical Engineering, Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain
| |
Collapse
|
8
|
Zhang L, Yuan Y, Zhang Y, Liu Y. Calcium hypochlorite pretreatment improves thermophilic digestion of waste activated sludge in an upflow anaerobic sludge blanket reactor. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 809:151130. [PMID: 34688757 DOI: 10.1016/j.scitotenv.2021.151130] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 10/16/2021] [Accepted: 10/17/2021] [Indexed: 06/13/2023]
Abstract
Anaerobic wasted activated sludge (WAS) digestion has been widely applied to reduce sludge volume and generate bioenergy in the form of methane. However, anaerobic WAS digestion performance is often challenged with poor hydrolysis of biomass cellular structures. In the present study, the feasibility of using calcium hypochlorite (Ca(ClO)2) to improve the thermophilic digestion of WAS was studied. Two thermophilic upflow anaerobic sludge bed (UASB) reactors (one with and one without Ca(ClO)2 pretreatment) were operated for 120 days under low and high organic loading rate (OLR) conditions, corresponding hydraulic retention time (HRT) of 10 days and 6 days, respectively. Both reactors achieved satisfied performance during the studied period. Under the low OLR condition, Ca(ClO)2 pretreatment significantly improved WAS total volatile solids (VS) removal efficiency (from 48.06 ± 2.63% to 57.34 ± 3.54%) and methane yield (from 289.2 ± 27.6 to 362.2 ± 36.7 N mL/g VS). However, no significant improvement was observed under the high OLR condition. g_S1 and g_Fervidobacterium were predominant bacteria in the thermophilic UASB reactor fed with Ca(ClO)2 pretreated WAS. Methanosarcina was dominant archaea in both reactors. The treatment mechanism and application potential of using Ca(ClO)2 to enhance the WAS digestibility were further discussed.
Collapse
Affiliation(s)
- Lei Zhang
- Department of Civil and Environmental Engineering, University of Alberta, Edmonton, Canada
| | - Yiyang Yuan
- Department of Civil and Environmental Engineering, University of Alberta, Edmonton, Canada
| | - Yingdi Zhang
- Department of Civil and Environmental Engineering, University of Alberta, Edmonton, Canada
| | - Yang Liu
- Department of Civil and Environmental Engineering, University of Alberta, Edmonton, Canada.
| |
Collapse
|
9
|
Enhanced ex-situ biomethanation of hydrogen and carbon dioxide in a trickling filter bed reactor. Biochem Eng J 2022. [DOI: 10.1016/j.bej.2021.108311] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
|
10
|
Wang Y, Wang Y, Zhang Z, Turap Y, Wang Y, Wang I, Wang Z, Wang W. Combined hydrothermal treatment, pyrolysis, and anaerobic digestion for removal of antibiotic resistance genes and energy recovery from antibiotic fermentation residues. BIORESOURCE TECHNOLOGY 2021; 337:125413. [PMID: 34175766 DOI: 10.1016/j.biortech.2021.125413] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 06/09/2021] [Accepted: 06/11/2021] [Indexed: 06/13/2023]
Abstract
A process combining hydrothermal treatment (HT), pyrolysis, and anaerobic digestion can efficiently treat antibiotic fermentation residues (AFR). The process characteristics and antibiotic resistance genes (ARGs) removal efficiencies of each unit have been investigated. HT of 180 °C improved the biodegradability and dewaterability of the AFR. Pyrolysis of 500 °C and upflow anaerobic sludge blanket (UASB) of 6.5 ± 0.5 kg COD•(m3•d)-1 recovered the organic matter in filter cake and filtrate of AFR. The biogas and pyrolysis gas can compensate the energy this system needs. HT of 180 °C could reduce 16S rRNA, ARGs, and mobile genetic elements (MGEs) by 2.3 to 7.4 logs. UASB increased the copy numbers of ARGs and MGEs, but the relative abundances of ARGs normalized against 16S rRNA were significantly declined. The ARGs and MGEs were enriched in suspended solids of digestate. The application of this process can promote the resources recycling of fermentation waste.
Collapse
Affiliation(s)
- Yidi Wang
- School of Environment, Tsinghua University, Beijing 100084, China
| | - Yongya Wang
- School of Environment, Tsinghua University, Beijing 100084, China; Department of Material Chemistry, Huzhou University, Huzhou 313000, China
| | - Zhe Zhang
- School of Environment, Tsinghua University, Beijing 100084, China
| | - Yusan Turap
- School of Environment, Tsinghua University, Beijing 100084, China
| | - Yongkang Wang
- School of Environment, Tsinghua University, Beijing 100084, China
| | - Iwei Wang
- School of Environment, Tsinghua University, Beijing 100084, China
| | - Zhentong Wang
- School of Environment, Tsinghua University, Beijing 100084, China
| | - Wei Wang
- School of Environment, Tsinghua University, Beijing 100084, China.
| |
Collapse
|