| 1. |
- 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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| 2. |
- Borzooei, Sina, et al.
(författare)
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Application of unsupervised learning and process simulation for energy optimization of a WWTP under various weather conditions
- 2020
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Ingår i: Water Science and Technology. - : IWA PUBLISHING. - 0273-1223 .- 1996-9732. ; 81:8, s. 1541-1551
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Tidskriftsartikel (refereegranskat)abstract
- This paper outlines a hybrid modeling approach to facilitate weather-based operation and energy optimization for the largest Italian wastewater treatment plant (WWTP). Two clustering methods,K-means algorithm and Gaussian mixture model (GMM) based on the expectation-maximization (EM) algorithm, were applied to an extensive dataset of historical and meteorological records. This study addresses the problem of determining the intrinsic structure of clustered data when no information other than the observed values is available. Two quantitative indexes, namely the Bayesian information criterion (BIC) and the Silhouette coefficient using Euclidean distance, as well as two general criteria, were implemented to assess the clustering quality. Furthermore, seven weather-based influent scenarios were introduced to the process simulation model, and sets of aeration strategies are proposed. The results indicate that incorporating weather-based aeration strategies in the operation of the WWTP improves plant energy efficiency.
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| 3. |
- Bürger, R., et al.
(författare)
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A review of flux identification methods for models of sedimentation
- 2020
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Ingår i: Water science and technology : a journal of the International Association on Water Pollution Research. - : IWA Publishing. - 0273-1223. ; 81:8, s. 1715-1722
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Tidskriftsartikel (refereegranskat)abstract
- Most models of sedimentation contain the nonlinear hindered-settling flux function. If one assumes ideal conditions and no compression, then there exist several theoretically possible ways of identifying a large portion of the flux function from only one experiment by means of formulas derived from the theory of solutions of partial differential equations. Previously used identification methods and recently published such, which are based on utilizing conical vessels or centrifuges, are reviewed and compared with synthetic data (simulated experiments). This means that the identification methods are evaluated from a theoretical viewpoint without experimental errors or difficulties. The main contribution of the recent methods reviewed is that they, in theory, can identify a large portion of the flux function from a single experiment, in contrast to the traditional method that provides one point on the flux curve from each test. The new methods lay the foundation of rapid flux identification; however, experimental procedures need to be elaborated.
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| 4. |
- Bürger, Raimund, et al.
(författare)
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Simulation and control of dissolved air flotation and column froth flotation with simultaneous sedimentation
- 2020
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Ingår i: Water science and technology : a journal of the International Association on Water Pollution Research. - : IWA Publishing. - 0273-1223. ; 81:8, s. 1723-1732
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Tidskriftsartikel (refereegranskat)abstract
- Flotation is a separation process where particles or droplets are removed from a suspension with the aid of floating gas bubbles. Applications include dissolved air flotation (DAF) in industrial wastewater treatment and column froth flotation (CFF) in wastewater treatment and mineral processing. One-dimensional models of flotation have been limited to steady-state situations for half a century by means of the drift-flux theory. A newly developed dynamic one-dimensional model formulated in terms of partial differential equations can be used to predict the process of simultaneous flotation of bubbles and sedimentation of particles that are not attached to bubbles. The governing model is a pair of first-order conservation laws for the aggregate and solids volume fractions as functions of height and time. An analysis of nonlinear ingredients of the governing equations helps to identify desired steady-state operating conditions. These can be chosen by means of operating charts, which are diagrams that visualize regions of admissible values of the volumetric flows of the feed input and underflow outlet. This is detailed for the DAF thickening process. Dynamic simulations are obtained with a recently developed numerical method. Responses to control actions are demonstrated with scenarios in CFF and DAF.
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| 5. |
- Guyonvarch, Estelle, et al.
(författare)
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Quantifying the sources of uncertainty when calculating the limiting flux in secondary settling tanks using iCFD
- 2020
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 81:2, s. 241-252
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Tidskriftsartikel (refereegranskat)abstract
- Solids-flux theory (SFT) and state-point analysis (SPA) are used for the design, operation and control of secondary settling tanks (SSTs). The objectives of this study were to assess uncertainties, propagating from flow and solids loading boundary conditions as well as compression settling behaviour to the calculation of the limiting flux (JL) and the limiting solids concentration (XL). The interpreted computational fluid dynamics (iCFD) simulation model was used to predict one-dimensional local concentrations and limiting solids fluxes as a function of loading and design boundary conditions. A two-level fractional factorial design of experiments was used to infer the relative significance of factors unaccounted for in conventional SPA. To move away from using semi-arbitrary safety factors, a systematic approach was proposed to calculate the maximum SST capacity by employing a factor of 23% and a regression meta-model to correct values of JL and XL, respectively – critical for abating hydraulic effects under wet-weather flow conditions.
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| 6. |
- Hosseini, Seyyed Hasan, et al.
(författare)
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Evaluation of a new X-band weather radar for operational use in south Sweden
- 2020
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 81:8, s. 1623-1635
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Tidskriftsartikel (refereegranskat)abstract
- The performance of a new type of X-band Weather Radar (WR) for Sweden during a pilot run is studied. Compared to the conventional C-band WRs, the X-band WR covers a smaller area but with a higher spatiotemporal resolution, making it suitable for urban hydrological applications. Rainfall estimations from different elevation angles of the radar (levels) are compared at one-minute and single-event timescales with the observations of several rain gauges at different ranges using hyetographs. In general, the estimations aligned well with observations and the best match appeared for ranges as long as 5–10 km. Seemingly, radar estimations suffered from overshooting of lower lying showers by higher level scans in longer ranges (19–30 km) and from the reflectivity contamination due to moving objects in short ranges (<1 km). Also, the effective range of the radar dropped sharply for the moments when a cloudburst was located over the radar. Although various sources of error could affect the X-band WR rainfall estimates, higher resolution spatiotemporal rainfall monitoring for wider areas will benefit from an integration of data from a network of X-band WRs.
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| 7. |
- Ivan, Heidi Lynn, 1996-, et al.
(författare)
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Exploring the effects of faults on the performance of a biological wastewater treatment process
- 2024
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 90:2, s. 474-489
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Tidskriftsartikel (refereegranskat)abstract
- To prioritise which faults should be detected in a biological wastewater treatment process, and with what level of urgency, it is necessary to understand the effect that they have on the process. Using the Benchmark Simulation Model No. 1 and 2. (BSM1 and BSM2), several process and sensor faults were considered and their impacts on various cost, quality, and controller performance evaluation metrics analysed. Both the cost of treating the wastewater and the quality of the effluent were impacted in varying degrees of severity by the faults tested. The most influential faults in both models were decreases to autotrophic and heterotrophic growth rates, decreases to the heterotrophic death rate, and the inhabitation fault. It was shown that only larger fault sizes were significant, and the required speed of detection is dependent on the fault profile. Prioritising detection of the most influential faults was shown to have significant effects on monitoring requirements for fault detection and the subsequent complexity required of a fault detection system. A valuable takeaway was the similarity of results from BSM1 and BSM2; the consistency of the influential process faults suggests that systems that can be described by these models are likely affected by the same faults.
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| 8. |
- Lindblom, E., et al.
(författare)
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Identification of behavioural model input data sets for WWTP uncertainty analysis
- 2020
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Ingår i: Water science and technology : a journal of the International Association on Water Pollution Research. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 81:8, s. 1558-1568
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Tidskriftsartikel (refereegranskat)abstract
- Uncertainty analysis is important for wastewater treatment plant (WWTP) model applications. An important aspect of uncertainty analysis is the identification and proper quantification of sources of uncertainty. In this contribution, a methodology to identify an ensemble of behavioural model representations (combinations of input data, model structure and parameter values) is presented and evaluated. The outcome is a multivariate conditional distribution of input data that is used for generating samples of likely inputs (such as Monte Carlo input samples) to perform WWTP model uncertainty analysis. This article presents an approach to verify uncertainty distributions of input data (otherwise often assumed) by using historical observations and actual plant data.
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| 9. |
- Lindblom, Erik U., et al.
(författare)
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Comparison of guideline- and model-based WWTP design for uncertain influent conditions
- 2023
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 87:1, s. 218-227
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Tidskriftsartikel (refereegranskat)abstract
- In this study, two methods for wastewater treatment plant (WWTP) dimensioning were compared: (1) a traditional guideline-based approach, and (2) a mechanistic model-based approach. The design outputs depended on uncertainties in correlated influent concentrations, which emphasises the importance of uncertainty analysis. The results showed that model-based design could simplify and reduce the time required for uncertainty and sensitivity analysis compared to a conventional design approach, in which the equations are solved manually and iteratively. A benefit of the conventional design approach was the simple interpretation of which factors limited the design capacity. In the end, this study shows the potential, as well as the need for, model-based design of WWTPs.
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| 10. |
- Lovisa Andersson, Sofia, et al.
(författare)
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Evaluation of environmental impacts for future influent scenarios using a model-based approach
- 2020
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Ingår i: Water science and technology : a journal of the International Association on Water Pollution Research. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 81:8, s. 1615-1622
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Tidskriftsartikel (refereegranskat)abstract
- Changes in dilution of wastewater to a treatment plant due to infiltration or surface runoff can have a great impact on treatment process performance. This paper presents a model-based approach in which realistic influent scenarios are generated and used as inputs to a dynamic plant-wide process model of the wastewater treatment plant. The simulated operation is subsequently evaluated using life-cycle assessment (LCA) to quantify the environmental impacts of the future influent scenarios. The results show that increased infiltration led to higher environmental impact per kg nitrogen removed. The increase in surface runoff had a minor impact.
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