| 1. |
- Flores-Alsina, Xavier, et al.
(författare)
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A plant-wide aqueous phase chemistry module describing pH variations and ion speciation/pairing in wastewater treatment process models.
- 2015
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Ingår i: Water Research. - : Elsevier BV. - 1879-2448 .- 0043-1354. ; 85, s. 255-265
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Tidskriftsartikel (refereegranskat)abstract
- There is a growing interest within the Wastewater Treatment Plant (WWTP) modelling community to correctly describe physico-chemical processes after many years of mainly focusing on biokinetics. Indeed, future modelling needs, such as a plant-wide phosphorus (P) description, require a major, but unavoidable, additional degree of complexity when representing cationic/anionic behaviour in Activated Sludge (AS)/Anaerobic Digestion (AD) systems. In this paper, a plant-wide aqueous phase chemistry module describing pH variations plus ion speciation/pairing is presented and interfaced with industry standard models. The module accounts for extensive consideration of non-ideality, including ion activities instead of molar concentrations and complex ion pairing. The general equilibria are formulated as a set of Differential Algebraic Equations (DAEs) instead of Ordinary Differential Equations (ODEs) in order to reduce the overall stiffness of the system, thereby enhancing simulation speed. Additionally, a multi-dimensional version of the Newton-Raphson algorithm is applied to handle the existing multiple algebraic inter-dependencies. The latter is reinforced with the Simulated Annealing method to increase the robustness of the solver making the system not so dependant of the initial conditions. Simulation results show pH predictions when describing Biological Nutrient Removal (BNR) by the activated sludge models (ASM) 1, 2d and 3 comparing the performance of a nitrogen removal (WWTP1) and a combined nitrogen and phosphorus removal (WWTP2) treatment plant configuration under different anaerobic/anoxic/aerobic conditions. The same framework is implemented in the Benchmark Simulation Model No. 2 (BSM2) version of the Anaerobic Digestion Model No. 1 (ADM1) (WWTP3) as well, predicting pH values at different cationic/anionic loads. In this way, the general applicability/flexibility of the proposed approach is demonstrated, by implementing the aqueous phase chemistry module in some of the most frequently used WWTP process simulation models. Finally, it is shown how traditional wastewater modelling studies can be complemented with a rigorous description of aqueous phase and ion chemistry (pH, speciation, complexation).
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| 2. |
- 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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| 3. |
- 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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| 4. |
- Kazadi Mbamba, Christian, et al.
(författare)
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Plant-wide model-based analysis of iron dosage strategies for chemical phosphorus removal in wastewater treatment systems
- 2019
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Ingår i: Water Research. - : Elsevier BV. - 0043-1354 .- 1879-2448. ; 155, s. 12-25
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Tidskriftsartikel (refereegranskat)abstract
- Stringent phosphorus discharge standards (i.e. 0.15–0.3 g P.m −3 ) in the Baltic area will compel wastewater treatment practice to augment enhanced biological phosphorus removal (EBPR) with chemical precipitation using metal salts. This study examines control of iron chemical dosing for phosphorus removal under dynamic loading conditions to optimize operational aspects of a membrane biological reactor (MBR) pilot plant. An upgraded version of the Benchmark Simulation Model No. 2 (BSM2) with an improved physico-chemical framework (PCF) is used to develop a plant-wide model for the pilot plant. The PCF consists of an equilibrium approach describing ion speciation and pairing, kinetic minerals precipitation (such as hydrous ferric oxides (HFO) and FePO 4 ) as well as adsorption and co-precipitation. Model performance is assessed against data sets from the pilot plant, evaluating the capability to describe water and sludge lines across the treatment process under steady-state operation. Simulated phosphorus differed as little as 5–10% (relative) from measured phosphorus, indicating that the model was representative of reality. The study also shows that environmental factors such as pH, as well operating conditions such as Fe/P molar ratios (1, 1.5 and 2), influence the concentration of dissolved phosphate in the effluent. The time constant of simultaneous precipitation in the calibrated model, due to a step change decrease/increase in FeSO 4 dosage, was found to be roughly 5 days, indicating a slow dynamic response due to a multi-step process involving dissolution, oxidation, precipitation, aging, adsorption and co-precipitation. The persistence effect of accumulated iron-precipitates (HFO particulates) in the activated sludge seemed important for phosphorus removal, and therefore solids retention time plays a crucial role according to the model. The aerobic tank was deemed to be the most suitable dosing location for FeSO 4 addition, due to high dissolved oxygen levels and good mixing conditions. Finally, dynamic model-based analyses show the benefits of using automatic control when dosing chemicals. © 2019 Elsevier Ltd
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| 5. |
- 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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| 6. |
- 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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