| 1. |
- Glasbey, JC, et al.
(författare)
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- 2021
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swepub:Mat__t
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| 6. |
- Jeppsson, Ulf, et al.
(författare)
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Benchmark simulation models, quo vadis?
- 2013
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 68:1, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- As the work of the IWA Task Group on Benchmarking of Control Strategies for wastewater treatment plants (WWTPs) is coming to an end, it is essential to disseminate the knowledge gained. For this reason, all authors of the IWA Scientific and Technical Report on benchmarking have come together to provide their insights, highlighting areas where knowledge may still be deficient and where new opportunities are emerging, and to propose potential avenues for future development and application of the general benchmarking framework and its associated tools. The paper focuses on the topics of temporal and spatial extension, process modifications within the WWTP, the realism of models, control strategy extensions and the potential for new evaluation tools within the existing benchmark system. We find that there are major opportunities for application within all of these areas, either from existing work already being done within the context of the benchmarking simulation models (BSMs) or applicable work in the wider literature. Of key importance is increasing capability, usability and transparency of the BSM package while avoiding unnecessary complexity.
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| 7. |
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| 8. |
- Solon, K., et al.
(författare)
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Plant-wide modelling of phosphorus transformations in wastewater treatment systems : Impacts of control and operational strategies
- 2017
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Ingår i: Water Research. - : Elsevier BV. - 0043-1354. ; 113, s. 97-110
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this paper is to report the effects that control/operational strategies may have on plant-wide phosphorus (P) transformations in wastewater treatment plants (WWTP). The development of a new set of biological (activated sludge, anaerobic digestion), physico-chemical (aqueous phase, precipitation, mass transfer) process models and model interfaces (between water and sludge line) were required to describe the required tri-phasic (gas, liquid, solid) compound transformations and the close interlinks between the P and the sulfur (S) and iron (Fe) cycles. A modified version of the Benchmark Simulation Model No. 2 (BSM2) (open loop) is used as test platform upon which three different operational alternatives (A1, A2, A3) are evaluated. Rigorous sensor and actuator models are also included in order to reproduce realistic control actions. Model-based analysis shows that the combination of an ammonium (SNHX ) and total suspended solids (XTSS) control strategy (A1) better adapts the system to influent dynamics, improves phosphate (SPO4 ) accumulation by phosphorus accumulating organisms (XPAO) (41%), increases nitrification/denitrification efficiency (18%) and reduces aeration energy (Eaeration) (21%). The addition of iron XFeCl3 ) for chemical P removal (A2) promotes the formation of ferric oxides (XHFO−H, XHFO−L), phosphate adsorption (XHFO−H,P, XHFO−L,P), co-precipitation (XHFO−H,P,old, XHFO−L,P,old) and consequently reduces the P levels in the effluent (from 2.8 to 0.9 g P.m−3). This also has an impact on the sludge line, with hydrogen sulfide production (GH2S) reduced (36%) due to iron sulfide (XFeS) precipitation. As a consequence, there is also a slightly higher energy production (Eproduction) from biogas. Lastly, the inclusion of a stripping and crystallization unit (A3) for P recovery reduces the quantity of P in the anaerobic digester supernatant returning to the water line and allows potential struvite (XMgNH4PO4 ) recovery ranging from 69 to 227 kg.day−1 depending on: (1) airflow (Qstripping); and, (2) magnesium (QMg(OH)2 ) addition. All the proposed alternatives are evaluated from an environmental and economical point of view using appropriate performance indices. Finally, some deficiencies and opportunities of the proposed approach when performing (plant-wide) wastewater treatment modelling/engineering projects are discussed.
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| 12. |
- Batstone, Damien, et al.
(författare)
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Kinetics of thermophilic, anaerobic oxidation of straight and branched chain butyrate and valerate
- 2003
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Ingår i: Biotechnology and Bioengineering. - : Wiley. - 1097-0290 .- 0006-3592. ; 84:2, s. 195-204
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Tidskriftsartikel (refereegranskat)abstract
- The degradation kinetics of normal and branched chain butyrate and valerate are important in protein-fed anaerobic systems, as a number of amino acids degrade to these organic acids. Including activated and primary wastewater sludge digesters, the majority of full-scale systems digest feeds with a significant or major fraction of COD as protein. This study assesses the validity of using a common kinetic parameter set and biological catalyst to represent butyrate, n-valerate, and i-valerate degradation in dynamic models. The i-valerate degradation stoichiometry in a continuous, mixed population system is also addressed, extending previous pure-culture and batch studies. A previously published mathematical model was modified to allow competitive uptake of i-valerate, and used to model a thermophilic manure digester operated over 180 days. The digester was periodically pulsed with straight and branched chain butyrate and valerate. Parameters were separately optimized to describe butyrate, i-valerate, and n-valerate degradation, as well as a lumped set optimized for all three substrates, and nonlinear, correlated parameter spaces estimated using an F distribution in the objective function (A Each parameter set occupied mutually exclusive parameter spaces, indicating that all were statistically different from each other. However, qualitatively, the influence on model outputs was similar, and the lumped set would be reasonable for mixed acid digestion. The main characteristic not represented by Monod kinetics was a delay in i-valerate uptake, and was compensated for by a decreased maximum uptake rate (k(m)). Therefore, the kinetics need modification if fed predominantly i-valerate. Butyrate (i- and n-) and n-valerate could be modeled using stoichiometry consistent with beta-oxidation degradation pathways. However, i-valerate produced acetate only, supporting the stoichiometry of a reaction determined by other researchers in pure culture. Therefore, lumping i-valerate stoichiometry with that of n-valerate will not allow good system representation, especially when the feed consists of proteins high in leucine (which produces i-valerate), and the modified model structure and stoichiometry as proposed here should be used. This requires no additional kinetic parameters and one additional dynamic concentration state variable (i-valerate) in addition to the variables in the base model.
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| 13. |
- Feldman, H., et al.
(författare)
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Assessing the effects of intra-granule precipitation in a full-scale industrial anaerobic digester
- 2019
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 79:7, s. 1327-1337
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a multi-scale model is used to assess the multiple mineral precipitation potential in a full-scale anaerobic granular sludge system. Reactor behaviour is analysed under different operational conditions (addition/no addition of reject water from dewatering of lime-stabilized biomass) and periods of time (short/long term). Model predictions suggest that a higher contribution of reject water promotes the risk of intra-granule CaCO3 formation as a result of the increased quantity of calcium arriving with that stream combined with strong pH gradients within the biofilm. The distribution of these precipitates depends on: (i) reactor height; and (ii) granule size. The study also exposes the potential undesirable effects of the long-term addition of reject water (a decrease in energy recovery of 20% over a 100-day period), caused by loss in biomass activity (due to microbial displacement), and the reduced buffer capacity. This demonstrates how both short-term and long-term operational conditions may affect the formation of precipitates within anaerobic granules, and how it may influence methane production and consequently energy recovery.
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| 14. |
- Feldman, H, et al.
(författare)
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Modelling an industrial anaerobic granular reactor using a multi-scale approach
- 2017
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Ingår i: Water Research. - : Elsevier BV. - 0043-1354. ; 126, s. 488-500
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this paper is to show the results of an industrial project dealing with modelling of anaerobic digesters. A multi-scale mathematical approach is developed to describe reactor hydrodynamics, granule growth/distribution and microbial competition/inhibition for substrate/space within the biofilm. The main biochemical and physico-chemical processes in the model are based on the Anaerobic Digestion Model No 1 (ADM1) extended with the fate of phosphorus (P), sulfur (S) and ethanol (Et−OH). Wastewater dynamic conditions are reproduced and data frequency increased using the Benchmark Simulation Model No 2 (BSM2) influent generator. All models are tested using two plant data sets corresponding to different operational periods (#D1, #D2). Simulation results reveal that the proposed approach can satisfactorily describe the transformation of organics, nutrients and minerals, the production of methane, carbon dioxide and sulfide and the potential formation of precipitates within the bulk (average deviation between computer simulations and measurements for both #D1, #D2 is around 10%). Model predictions suggest a stratified structure within the granule which is the result of: 1) applied loading rates, 2) mass transfer limitations and 3) specific (bacterial) affinity for substrate. Hence, inerts (XI) and methanogens (Xac) are situated in the inner zone, and this fraction lowers as the radius increases favouring the presence of acidogens (Xsu,Xaa, Xfa) and acetogens (Xc4,Xpro). Additional simulations show the effects on the overall process performance when operational (pH) and loading (S:COD) conditions are modified. Lastly, the effect of intra-granular precipitation on the overall organic/inorganic distribution is assessed at: 1) different times; and, 2) reactor heights. Finally, the possibilities and opportunities offered by the proposed approach for conducting engineering optimization projects are discussed.
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| 15. |
- Flores-Alsina, X., et al.
(författare)
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Evaluation of anaerobic digestion post-treatment options using an integrated model-based approach
- 2019
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Ingår i: Water Research. - : Elsevier BV. - 0043-1354. ; 156, s. 264-276
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this paper is to present the main results of an engineering-research project dealing with model-based evaluation of waste streams treatment from a biotech company. This has been extensively done in domestic treatment systems, but is equally important, and with different challenges in industrial wastewater treatment. A new set of biological (activated sludge, anaerobic digestion), physicochemical (aqueous phase, precipitation, mass transfer) process models and model interfaces are required to describe removal of organics in an upflow anaerobic sludge blanket (UASB) reactor plus either traditional nitrification/denitrification (A 1 ) or partial nitritation (PN)/anammox (ANX) (A 2 ) processes. Model-based analysis shows that option A 1 requires a decrease in digestion energy recovery (E recovery ) in order to have enough organic substrate for subsequent post NO 3 reduction treatment (95 kWh.kg N −1 ). In contrast, A 2 in an aerobic granular sludge reactor allows for higher UASB conversion since N removal is carried out autotrophically. The study also reveals that the addition of an aerated pre-treatment unit prior to the PN/ANX (A 2 ) reactor promotes COD and H 2 S oxidation, CO 2 and CH 4 stripping, a pH increase (up to 8.5) and a reduction of the risk of intra-granular precipitation as well as sulfide inhibition. Simulations indicate clear differences regarding the microbial distribution/abundance within the biofilm in A 2 when comparing the two operational modes. Final results show the effects of different loading and operational conditions; dissolved oxygen (DO), Total Suspended Solids (TSS op ), energy recovery (E recovery ); on the overall process performance; N removal, aeration energy (E aeration ), net energy production (E recovery ); using response surfaces, highlighting the need of integrated approaches to avoid sub-optimal outcomes. The study shows the benefits of virtual plant simulation and demonstrates the potential of model-based evaluation when process engineers in industry have to decide between competing options.
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| 16. |
- Gernaey, K V, et al.
(författare)
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Impact of reactive settler models on simulated WWTP performance
- 2006
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 53:1, s. 159-167
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Tidskriftsartikel (refereegranskat)abstract
- Including a reactive settler model in a wastewater treatment plant model allows representation of the biological reactions taking place in the sludge blanket in the settler, something that is neglected in many simulation studies. The idea of including a reactive settler model is investigated for an ASM1 case study. Simulations with a whole plant model including the non-reactive Takacs settler model are used as a reference, and are compared to simulation results considering two reactive settler models. The first is a return sludge model block removing oxygen and a user-defined fraction of nitrate, combined with a non-reactive Takacs settler. The second is a fully reactive ASM1 Takacs settler model. Simulations with the ASM1 reactive settler model predicted a 15.3% and 7.4% improvement of the simulated N removal performance, for constant (steady-state) and dynamic influent conditions respectively. The oxygen/nitrate return sludge model block predicts a 10% improvement of N removal performance under dynamic conditions, and might be the better modelling option for ASM1 plants: it is computationally more efficient and it will not overrate the importance of decay processes in the settler.
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| 17. |
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| 18. |
- Rogers, Simon N., et al.
(författare)
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Variations in concerns reported on the patient concerns inventory in patients with head and neck cancer from different health settings across the world
- 2020
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Ingår i: Head and Neck. - : Wiley. - 1043-3074 .- 1097-0347. ; 42:3, s. 498-512
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Tidskriftsartikel (refereegranskat)abstract
- Background The aim was to collate and contrast patient concerns from a range of different head and neck cancer follow-up clinics around the world. Also, we sought to explore the relationship, if any, between responses to the patient concerns inventory (PCI) and overall quality of life (QOL). Methods Nineteen units participated with intention of including 100 patients per site as close to a consecutive series as possible in order to minimize selection bias. Results There were 2136 patients with a median total number of PCI items selected of 5 (2-10). "Fear of the cancer returning" (39%) and "dry mouth" (37%) were most common. Twenty-five percent (524) reported less than good QOL. Conclusion There was considerable variation between units in the number of items selected and in overall QOL, even after allowing for case-mix variables. There was a strong progressive association between the number of PCI items and QOL.
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| 19. |
- Solon, Kimberly, et al.
(författare)
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Effects of ionic strength and ion pairing on (plant-wide) modelling of anaerobic digestion.
- 2015
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Ingår i: Water Research. - : Elsevier BV. - 1879-2448 .- 0043-1354. ; 70:March, s. 235-245
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Tidskriftsartikel (refereegranskat)abstract
- Plant-wide models of wastewater treatment (such as the Benchmark Simulation Model No. 2 or BSM2) are gaining popularity for use in holistic virtual studies of treatment plant control and operations. The objective of this study is to show the influence of ionic strength (as activity corrections) and ion pairing on modelling of anaerobic digestion processes in such plant-wide models of wastewater treatment. Using the BSM2 as a case study with a number of model variants and cationic load scenarios, this paper presents the effects of an improved physico-chemical description on model predictions and overall plant performance indicators, namely effluent quality index (EQI) and operational cost index (OCI). The acid-base equilibria implemented in the Anaerobic Digestion Model No. 1 (ADM1) are modified to account for non-ideal aqueous-phase chemistry. The model corrects for ionic strength via the Davies approach to consider chemical activities instead of molar concentrations. A speciation sub-routine based on a multi-dimensional Newton-Raphson (NR) iteration method is developed to address algebraic interdependencies. The model also includes ion pairs that play an important role in wastewater treatment. The paper describes: 1) how the anaerobic digester performance is affected by physico-chemical corrections; 2) the effect on pH and the anaerobic digestion products (CO2, CH4 and H2); and, 3) how these variations are propagated from the sludge treatment to the water line. Results at high ionic strength demonstrate that corrections to account for non-ideal conditions lead to significant differences in predicted process performance (up to 18% for effluent quality and 7% for operational cost) but that for pH prediction, activity corrections are more important than ion pairing effects. Both are likely to be required when precipitation is to be modelled.
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| 20. |
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