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Blach T, Engelhart M. Electrochemical oxidation of refractory compounds from hydrothermal carbonization process waters. CHEMOSPHERE 2024; 352:141310. [PMID: 38320739 DOI: 10.1016/j.chemosphere.2024.141310] [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: 10/12/2023] [Revised: 01/20/2024] [Accepted: 01/25/2024] [Indexed: 02/10/2024]
Abstract
Hydrothermal carbonization (HTC) is an emerging technology for treating sewage sludge. However, the resulting HTC process water is heavily contaminated with various carbonaceous and nitrogenous components, some of them being non-biodegradable. To implement HTC as a full-scale treatment alternative for sewage sludge, effective concepts for treating process water are crucial. This study focuses on the electrochemical oxidation (EO) using a boron-doped diamond electrode to treat one HTC process waters with different pretreatments: (i) without pretreatment, (ii) biologically pretreated with chemical oxygen demand (COD) removal, (iii) biologically pretreated with nitrification and denitrification. The EO removed COD of all HTC process waters by over 97%, but as COD concentrations decreased, the instantaneous current efficiency (ICE) dropped below 5% and energy consumption increased. The organically bound and refractory nitrogen was completely mineralized and converted to mainly NO3-N. After EO of process waters without nitrification/denitrification, nitrogen was present as NO3-N with up to 730 mg/L and NH4-N with up to 1813 mg/L. Such high ammonium concentrations treatment could be interesting for nitrogen recovery. In addition, the toxicity towards Vibrio fischeri could be reduced to a large extent. The findings suggest that EO after a biological step with COD removal is a viable solution for HTC process water treatment.
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Affiliation(s)
- T Blach
- Technical University of Darmstadt, Institute IWAR, Franziska-Braun-Str. 7, 64287, Darmstadt, Germany.
| | - M Engelhart
- Technical University of Darmstadt, Institute IWAR, Franziska-Braun-Str. 7, 64287, Darmstadt, Germany
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Liu L, Zhai Y, Wang H, Liu X, Liu X, Wang Z, Zhou Y, Zhu Y, Xu M. Treatment of sewage sludge hydrothermal carbonization aqueous phase by Fe(II)/CaO 2 system: Oxidation behaviors and mechanism of organic compounds. WASTE MANAGEMENT (NEW YORK, N.Y.) 2023; 158:164-175. [PMID: 36716656 DOI: 10.1016/j.wasman.2023.01.016] [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: 09/25/2022] [Revised: 01/13/2023] [Accepted: 01/15/2023] [Indexed: 06/18/2023]
Abstract
The Fe(II)/CaO2 system with a stable oxidant and a low-cost homogeneous activating agent has been considered as a prospective process for the disposal of wastewater. The system was constructed to treat sewage sludge hydrothermal carbonization aqueous phase (HTC-AP) in this study. As the hydrothermal temperature increased, the organics in the HTC-AP were first decomposed and then cyclized, while the Maillard reaction occurs throughout the stage. The oxidation efficiency of the Fe(II)/CaO2 system was related to the composition of organics in HTC-AP, and the removal of dissolved organic carbon (DOC) by the system was 38.56 % in the HTC-AP obtained by hydrothermal treatment at 220 °C. Redundancy analysis showed that the low molecular weight organics, hydrophobic acids, and hydrophobic neutral components were beneficial to DOC removal, while Maillard products and cyclization products were hard to be oxidized to CO2 and H2O. The CN functional group of the protein facilitated DOC removal, and some organics in HTC-AP were oxidized to acids and phenols. The energy input to remove DOC in Fe(II)/CaO2 system was 27.74 MJ per kg carbon. This study provides a low-energy consumption Fe(II)/CaO2 system for the post-treatment of HTC-APs and explores the applicability of the system.
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Affiliation(s)
- Liming Liu
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, PR China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, PR China
| | - Yunbo Zhai
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, PR China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, PR China.
| | - Hongxia Wang
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, PR China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, PR China
| | - Xiangmin Liu
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, PR China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, PR China
| | - Xiaoping Liu
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, PR China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, PR China
| | - Zhexian Wang
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, PR China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, PR China
| | - Yin Zhou
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, PR China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, PR China
| | - Yun Zhu
- Office of Scientific R& D, Hunan University, Changsha 410082, PR China
| | - Min Xu
- Chinese Academy of Environmental Planning, Beijing 100012, PR China
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Kick C, Uchaikina A, Apfelbacher A, Daschner R, Helmreich B, Hornung A. Aqueous phase of thermo-catalytic reforming of sewage sludge – quantity, quality, and its electrooxidative treatment by a boron-doped diamond electrode. Sep Purif Technol 2022. [DOI: 10.1016/j.seppur.2021.120392] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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Silva Thomsen LB, Anastasakis K, Biller P. Wet oxidation of aqueous phase from hydrothermal liquefaction of sewage sludge. WATER RESEARCH 2022; 209:117863. [PMID: 34844067 DOI: 10.1016/j.watres.2021.117863] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 10/29/2021] [Accepted: 11/09/2021] [Indexed: 06/13/2023]
Abstract
Hydrothermal liquefaction (HTL) is a thermochemical process for the conversion of biomass into bio-crude oil. However, treatment of post-HTL aqueous by-products is an emerging issue towards the commercialisation of HTL technology. This study investigates the use of non-catalytic wet oxidation (WO) for the reduction of organic compounds and heat production at different temperatures (200-350 °C), residence times (RT) (2-180 min) and excess oxygen. The aqueous phase from HTL of sewage sludge is investigated, and 97.6% of the chemical oxygen demand (COD) and 96.1% of the total organic carbon (TOC) were removed at the highest temperature and retention time. The minimum energy requirement achieved was 9.6 kWh/kg COD removed at 200 °C for 180 min, and the exothermic reactions of the process can generate 28.3% of the required heat. GC-FID and -MS analysis revealed that the degradation of different groups of organic compounds generates acetic acid as an intermediate by-product of WO, being further oxidised at temperatures higher than 300 °C. NH4+and NH3 are generated from the decomposition of nitrogenated organic compounds showing the highest concentration of 704.5 mg NH4+ /L at 350 °C after 180 min.
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Affiliation(s)
- Lars Bjørn Silva Thomsen
- Department of Biological and Chemical Engineering, Aarhus University, Hangøvej 2, Aarhus N 8200, Denmark; WATEC - Centre for Water Technology, Aarhus University, Ny Munkegade 120, Aarhus 8000, Denmark
| | - Konstantinos Anastasakis
- Department of Biological and Chemical Engineering, Aarhus University, Hangøvej 2, Aarhus N 8200, Denmark; WATEC - Centre for Water Technology, Aarhus University, Ny Munkegade 120, Aarhus 8000, Denmark
| | - Patrick Biller
- Department of Biological and Chemical Engineering, Aarhus University, Hangøvej 2, Aarhus N 8200, Denmark; WATEC - Centre for Water Technology, Aarhus University, Ny Munkegade 120, Aarhus 8000, Denmark.
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