| 1. |
- Arnell, Magnus, et al.
(författare)
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Multi-objective performance assessment of wastewater treatment plants combining plant-wide process models and life cycle assessment
- 2017
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Ingår i: Journal of Water and Climate Change. - : IWA Publishing. - 2040-2244 .- 2408-9354. ; 8:4, s. 715-729
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Tidskriftsartikel (refereegranskat)abstract
- Multi-objective performance assessment of operational strategies at wastewater treatment plants (WWTPs) is a challenging task. The holistic perspective applied to evaluation of modern WWTPs, including not only effluent quality but also resource efficiency and recovery, global environmental impact and operational cost calls for assessment methods including both on- and off-site effects. In this study, a method combining dynamic process models – including greenhouse gas (GHG), detailed energy models and operational cost – and life cycle assessment (LCA) was developed. The method was applied and calibrated to a large Swedish WWTP. In a performance assessment study, changing the operational strategy to chemically enhanced primary treatment was evaluated. The results show that the primary objectives, to enhance bio-methane production and reduce GHG emissions were reached. Bio-methane production increased by 14% and the global warming potential decreased by 28%. However, due to increased consumption of chemicals, the operational cost increased by 87% and the LCA revealed that the abiotic depletion of elements and fossil resources increased by 77 and 305%, respectively. The results emphasize the importance of using plant-wide mechanistic models and life cycle analysis to capture both the dynamics of the plant and the potential environmental impacts.
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| 2. |
- Arnell, Magnus, et al.
(författare)
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Plant-wide modelling and analysis of WWTP temperature dynamics for sustainable heat recovery from wastewater
- 2021
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 84:4, s. 1023-1036
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Tidskriftsartikel (refereegranskat)abstract
- Wastewater heat recovery upstream of wastewater treatment plants (WWTP) poses a risk to treatment performance, i.e. the biological processes. In order to perform a sustainability analysis, a detailed prediction of the temperature dynamics over the WWTP is needed. A comprehensive set of heat balance equations was included in a plant-wide process model and validated for the WWTP in Linköping, Sweden, to predict temperature variations over the whole year in a temperate climate. A detailed model for the excess heat generation of biological processes was developed. The annual average temperature change from influent to effluent was 0.78°C with clear seasonal variations, wherein 45% of the temperature change arose from processes other than the activated sludge unit. To address this, plant-wide energy modelling was necessary to predict in-tank temperature in the biological treatment steps. The energy processes with the largest energy gains were solar radiation and biological processes, while the largest losses were from conduction, convection, and atmospheric radiation. Tanks with large surface areas showed a significant impact on the heat balance regardless of biological processes. Simulating a 3°C lower influent temperature, the temperature in the activated sludge unit dropped by 2.8°C, which had a negative impact on nitrogen removal
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| 3. |
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| 4. |
- Feldman, Hannah, et al.
(författare)
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Model-based analysis and optimization of a full-scale industrial high-rate anaerobic bioreactor
- 2018
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Ingår i: Biotechnology and Bioengineering. - : Wiley. - 0006-3592 .- 1097-0290. ; , s. 2726-2739
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this paper is to present the model-based optimization results of an anaerobic granular sludge internal circulation reactor. The International Water Association Anaerobic Digestion Model No. 1 extended with phosphorus (P), sulfur (S), and ethanol is used to describe the main biological and physico-chemical processes. The high-rate conditions within the reactor are simulated using a flow + reactor model comprised of a series of continuous stirred tank reactors followed by an ideal total suspended solids separation unit. Following parameter estimation by least squares on the measured data, the model had a relative mean error of 13 and 15% for data set #1 and data set #2, respectively. Response surfaces show that the reactor performance index (a metric combining energy recovery in the form of heat and electricity, as well as chemicals needed for pH control) could be improved by 45% when reactor pH is reduced down to 6.8. Model-based results reveal that influent S does not impose sufficient negative impacts on energy recovery (+5.7%, in MWh/day,+0.20 M€/year when influent S is removed) to warrant the cost of its removal (3.58 M€/year). In fact, the process could handle even higher S loads (ensuring the same degree of conversion) as long as the pH is maintained above 6.8. Nevertheless, a higher S load substantially increases the amount of added NaOH to maintain the desired operational pH (>25%) due to the acidic behavior of HS −. CO 2 stripping decreases the buffer capacity of the system and hence use of chemicals for pH control. Finally, the paper discusses the possibilities and limitations of the proposed approach, and how the results of this study will be put into practice.
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| 5. |
- Jeppsson, Ulf, et al.
(författare)
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An evaluation of a dynamic model of the secondary clarifier
- 1996
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223. ; 34:5, s. 19-26
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Tidskriftsartikel (refereegranskat)abstract
- The main objective of the paper is to support and illustrate recent theoretical results on the mathematical modelling of the secondary clarifier. A new settler model is compared with a traditional layer model by means of numerical simulations. Emphasis is put on the numerical solution's ability to approximate the analytical solution of the conservation law written as a non-linear partial differential equation. The new settler model is consistent in this respect. Another important conclusion is that a layer model dividing the settler into only ten layers (normally used in settler models) is too crude an approximation to capture the detailed dynamic behaviour of the settler. All simulations presented are performed with the settler models coupled to the IAWQ Activated Sludge Model No. 1.
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| 6. |
- Jeppsson, Ulf, et al.
(författare)
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On the modelling of the dynamic propagation of biological components in the secondary clarifier
- 1996
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223. ; 34:5, s. 85-92
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Tidskriftsartikel (refereegranskat)abstract
- When coupling a model of the biological reactor to a model of the settler, difficulties appear because of the different representations used for the particulate material. A combined model of the entire activated sludge process needs to include an algorithm for the dynamic propagation of the biological components of the particulate material through the secondary clarifier. In particular, this is of importance for an accurate description of the sludge that is recycled to the biological reactor. Two one-dimensional algorithms have been evaluated by means of numerical simulations. The first algorithm investigated is the one by Otterpohl and Freund in 1992 and some inherent problems of this method are discussed. For example, it will produce oscillating solutions as the number of layers in the settler model increases. Therefore, an alternative algorithm is proposed. It is based on a percentage vector that describes the different particulate biological components as fractions of the total suspended solids concentration. The vector is updated for every layer in the settler model by a robust numerical method. The algorithm is derived analytically, is computationally efficient and does not exhibit any oscillatory behaviour.
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| 7. |
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| 8. |
- Kazadi Mbamba, Christian, et al.
(författare)
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Modelling Industrial Symbiosis of Biogas Production and Industrial Wastewater Treatment Plants – Technical Report
- 2020
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The present-day treatment of pulp and paper mill effluents can be significantly improved by incorporating biogas production in the context of industrial symbiosis. In this work a new industrial symbiosis concept is presented, the focus being on modelling it in view of process optimization, design improvement and adoption by the pulp and paper industry. The concept consists of a first stage in which pulp and paper mill effluents are treated by high-rate anaerobic digestion in external circulation sludge bed (ECSB) reactors to produce biogas. In the second stage the removal of organic matter contained in the anaerobic effluent stream occurs through aerobic activated sludge treatment, aiming to achieve maximum sludge production with minimum aeration requirements. This sludge should in the case study then be co-digested with residues from fish farming industry to yield methane for energy production, nutrient-rich reject water that can be recycled to the activated sludge treatment for optimum microbial activities and production of a nutrient-rich soil amendment. The overall research aim was in this project to develop a mathematical model that describes the relevant process units and the dynamics of the different processes involving organic matter removal, biogas production and nutrient release. The plant-wide model used integrated activated sludge and anaerobic models with a physico-chemical modelling framework. Through systematic calibration good general agreement was obtained between the full-scale experimental and simulated results at steady state. Acceptable differences between measured and modelled biogas production (flow rate and methane concentration), nutrients release (N and P) and effluent quality (N, P and COD) of 2-3.2 %, 5.3-7.4 % and 1.4-1.9 %, respectively, were observed throughout the full-scale system. Model-based analysis shows that the model can predict and give insight on dynamic behaviours resulting from deliberate changes but also on disturbances in one of the systems and their subsequent impacts within the integrated plant. Additionally, the model allowed the prediction of nutrients release in anaerobic digestion and subsequent consumption upstream in the high-rate anaerobic system or activated sludge system. Simulations show that there is a need for imposing a basic control and operational strategy for efficient reject water recirculation to optimize the concentrations of N and P in the activated sludge system while also achieving nutrient levels required to meet the effluent discharge permits. Overall, the evaluated plant-wide model can jointly describe the relevant physico-chemical and biological processes and is therefore advocated as a tool for future extension of this type of industrial symbiosis concepts between biogas producers and industries producing large amounts of wastewater rich in organic material. The model can be used for design, multi-criteria performance assessment and optimization of different treatment plants.
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| 9. |
- Kazadi Mbamba, Christian, et al.
(författare)
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Modelling Industrial Symbiosis of BiogasProduction and Industrial WastewaterTreatment Plants – A Review
- 2019
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The present-day treatment of pulp and paper mill effluents can be significantly improvedby incorporating biogas production in the context of industrial symbiosis. In this work anew industrial symbiosis concept is presented, the focus being on modelling it in view ofprocess optimization, design improvement and adoption by the pulp and paper industry.The concept consists of a first stage in which pulp and paper mills effluents are treatedby high-rate anaerobic digestion in external circulation sludge bed (ECSB) reactors toproduce biogas. In the second stage the removal of organic matter contained in thedigestate stream occurs through aerobic activated sludge treatment, aiming to achievemaximum sludge production with minimum aeration requirements. This sludge shouldin the case study then be co-digested with fish-waste silage to yield methane for energyproduction, nutrients-rich reject water that can be recycled to the activated sludgetreatment for optimum microbial activities and, production of nutrient rich soilamendment. The overall research aim is to develop a mathematical model that describesthe relevant process units and the dynamics of the different processes involving organicmatter removal, biogas production and nutrients release. The review overall finds thatan integrated model is required to simulate this concept and should include recentdevelopments in activated sludge, anaerobic digestion and physico-chemical modelling.
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| 10. |
- Lindblom, Erik, et al.
(författare)
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Dynamic modelling of nitrous oxide emissions from three Swedish sludge liquor treatment systems
- 2016
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 73:4, s. 798-806
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this paper is to model the dynamics and validate the results of nitrous oxide (N2O) emissions from three Swedish nitrifying/denitrifying, nitritation and anammox systems treating real anaerobic digester sludge liquor. The Activated Sludge Model No. 1 is extended to describe N2O production by both heterotrophic and autotrophic denitrification. In addition, mass transfer equations are implemented to characterize the dynamics of N2O in the water and the gas phases. The biochemical model is simulated and validated for two hydraulic patterns: (1) a sequencing batch reactor; and (2) a moving-bed biofilm reactor. Results show that the calibrated model is partly capable of reproducing the behaviour of N2O as well as the nitritation/nitrification/denitrification dynamics. However, the results emphasize that additional work is required before N2O emissions from sludge liquor treatment plants can be generally predicted with high certainty by simulations. Continued efforts should focus on determining the switching conditions for different N2O formation pathways and, if full-scale data are used, more detailed modelling of the measurement devices might improve the conclusions that can be drawn.
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