| 1. |
- Samuelsson, Oscar, et al.
(författare)
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Fault signatures and bias progression in dissolved oxygen sensors
- 2018
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 78:5, s. 1034-1044
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Tidskriftsartikel (refereegranskat)abstract
- Biofilm fouling is known to impact the data quality of sensors, but little is known about the exact effects. We studied the effects of artificial and real biofilm fouling on dissolved oxygen (DO) sensors in full-scale water resource recovery facilities, and how this can automatically be detected. Biofilm fouling resulted in different drift direction and bias magnitudes for optical (OPT) and electrochemical (MEC) DO sensors. The OPT-sensor was more affected by biofilm fouling compared to the MEC-sensor, especially during summer conditions. A bias of 1 mg/L was detected by analysing the impulse response (IR) of the automatic air cleaning system in the DO sensor. The IR is an effect of a temporal increase in DO concentration during the automatic air cleaning. The IRs received distinct pattern changes that were matched with faults including: biofilm fouling, disturbances in the air supply to the cleaning system, and damaged sensor membrane, which can be used for fault diagnosis. The results highlight the importance of a condition-based sensor maintenance schedule in contrast to fixed cleaning intervals. Further, the results stress the importance of understanding and detecting bias due to biofilm fouling, in order to maintain a robust and resource-efficient process control.
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| 2. |
- Diehl, S., et al.
(författare)
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Steady-state analyses of activated sludge processes with plug-flow reactor
- 2017
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Ingår i: Journal of Environmental Chemical Engineering. - : Elsevier BV. - 2213-3437. ; 5:1, s. 795-809
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Tidskriftsartikel (refereegranskat)abstract
- Activated sludge processes (ASPs) consisting of a plug-flow reactor (PFR) and a settler are analyzed in steady-state operation using a reduced model consisting of one soluble substrate and one particulate biomass component modelling the dominating biological process. Monod biomass growth rate is assumed. Two settler models are studied. One is the commonly used ideal settler, or point settler, which is assumed to never be overloaded and to have unlimited flux capacity. The other recently published steady-state settler model includes hindered and compressive settling, and models a realistic limiting flux capacity. Generally, the steady-state concentration profiles within the PFR and the settler are governed by nonlinear ordinary differential equations. It is shown that the steady-state behaviour of the ASP can, however, be captured by equations without derivatives. New theoretical results are given, such as conditions by means of inequalities on input variables and parameters for a steady-state solution to exist. Another novel finding is that, if the incoming substrate concentration is increased from a low or moderate stationary value and the solids residence time is kept fixed, then this results in a lower effluent concentration in the new steady state. The steady-state equations are solved numerically for different operating conditions. For common parameter values, numerical solutions reveal that an ASP having a PFR, instead of a continuously stirred tank reactor, is far more efficient in reducing the effluent substrate concentration and this can be obtained for much lower recycle ratios, which reduces the pumping energy considerably.
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| 3. |
- Samuelsson, Oscar, et al.
(författare)
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Gaussian process regression for monitoring and fault detection of wastewater treatment processes
- 2017
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Ingår i: Water Science and Technology. - UK : IWA Publishing. - 0273-1223 .- 1996-9732. ; 75:12, s. 2952-2963
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Tidskriftsartikel (refereegranskat)abstract
- Monitoring and fault detection methods are increasingly important to achieve a robust and resource efficient operation of wastewater treatment plants (WWTPs). The purpose of this paper was to evaluate a promising machine learning method, Gaussian process regression (GPR), at WWTP monitoring applications. We evaluated GPR at two WWTP monitoring problems: estimate missing data in a flow rate signal (simulated data), and detect a drift in an ammonium sensor (real data). We showed that GPR with the standard estimation method, maximum likelihood estimation (GPR-MLE), suffered from local optima during estimation of kernel parameters, and did not give satisfactory results in a simulated case study. However, GPR with a state-of-the-art estimation method based on sequential Monte Carlo estimation (GPR-SMC) gave good predictions and did not suffer from local optima. Comparisons with simple standard methods revealed that GPR-SMC performed better than linear interpolation in estimating missing data in a noisy flow rate signal. We conclude that GPR-SMC is both a general and powerful method for monitoring full-scale WWTPs. However, this paper also shows that it does not always pay off to use more sophisticated methods. New methods should be critically compared against simpler methods, which might be good enough for some scenarios.
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| 4. |
- Zambrano, Jesús, et al.
(författare)
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A simple model for algae-bacteria interaction in photo-bioreactors
- 2016
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Ingår i: Algal Research. - : Elsevier. - 2211-9264. ; 19:nov, s. 155-161
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Tidskriftsartikel (refereegranskat)abstract
- This work presents a simple model to describe the consortia of algae-bacteria in a photo-bioreactor. The model is inspired by the Activated Sludge Model (ASM) structure, which includes different process rates and stoichiometric parameters. The model comprises two main biomass populations (algae and bacteria), two dissolved substrates (ammonium and nitrate) and two dissolved gases (oxygen and carbon dioxide) in the reactor. The model was calibrated with data from batch experiments performed in two lab-scale photo-bioreactors. A sensitivity analysis was done to identify the parameters to be considered for the model calibration. Results indicate that the maximum algae and bacteria growth rate, bacteria growth yield and half-saturation constant for carbon were the most sensitive parameters. Moreover, the comparison between the experiments and the model shows good agreement in terms of predicting the ammonium, nitrate and oxygen concentrations in the photo-bioreactor.
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| 5. |
- Corneo, Lorenzo, et al.
(författare)
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Service Level Agreements for Safe and Configurable Production Environments
- 2018
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Ingår i: IEEE International Conference on Emerging Technologies and Factory Automation, ETFA. - : IEEE. - 1946-0759 .- 1946-0740.
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Konferensbidrag (refereegranskat)abstract
- This paper focuses on Service Level Agreements (SLAs) for industrial applications that aim to port some of the control functionalities to the cloud. In such applications, industrial requirements should be reflected in SLAs. In this paper, we present an approach to integrate safety-related aspects of an industrial application to SLAs. We also present the approach in a use case. This is an initial attempt to enrich SLAs for industrial settings to consider safety aspects, which has not been investigated thoroughly before.
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| 6. |
- Eriksson, Mattias, et al.
(författare)
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Mapping of food waste quantification methodologies in the food services of Swedish municipalities
- 2018
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Ingår i: Resources, Conservation and Recycling. - : ELSEVIER SCIENCE BV. - 0921-3449 .- 1879-0658. ; 137, s. 191-199
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Tidskriftsartikel (refereegranskat)abstract
- Since food waste valorisation measures, like energy recovery, have limited possibilities to fully recover the resources invested in food production, there is a need to prevent food waste. Prevention is most important at the end of the value chain, where most sub-processes have already taken place, like in catering facilities. In Sweden, the public catering sector serves a large number of meals through municipal organisations, including schools, preschools and elderly care homes. Many of these organisations quantify food waste, but since Sweden has 290 municipalities with a high degree of independence, the possible variation is significant. This study therefore investigated how food waste is quantified, in order to help formulate a national standard for food waste quantification. Mapping of food waste quantification practices was conducted using a questionnaire and follow-up telephone calls, achieving a response rate of 93%. Of the 290 Swedish municipalities, 55% replied that they quantify food waste on central level. The most common practice at present is to quantify plate- and serving waste from school lunches during two weeks per year, and to compile waste data in spreadsheets and compare the values against the number of plates used, giving a result in grams per portion served. There are many similarities between municipalities, so there is great potential to implement a common standard that many municipalities already fulfil. This is important in order to gain acceptance and fast implementation, thereby speeding up the process of establishing a benchmark for food waste in the Swedish public sector catering sector.
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| 7. |
- Monghasemi, Nima, et al.
(författare)
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Rank-Based Assessment of Grid-Connected Rooftop Solar Panel Deployments Considering Scenarios for a Postponed Installation
- 2023
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Ingår i: Energies. - : MDPI. - 1996-1073. ; 16:21
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Tidskriftsartikel (refereegranskat)abstract
- Installing solar photovoltaic panels on building rooftops can help property managers generate renewable energy and reduce electricity costs. However, the existence of multiple efficiency indicators and ambiguity in interpreting these metrics limits the comparison of the performance of individual installation projects. This paper presents a methodology using data envelopment analysis to evaluate suitable candidates for rooftop solar panel installation. This approach integrates rooftop area, solar irradiation, temperature, costs, energy yield, and revenue to evaluate the relative efficiency of each building. To demonstrate the methodology, it was applied to rank 22 residential buildings, revealing the top performers for installation in 2022. The approach was subsequently adapted to assess potential outcomes under deferred implementation up to 2030, encompassing a diverse range of climate and pricing scenarios. Five installations were found to be optimal irrespective of the future scenarios. In addition, a super-efficiency approach was applied to overcome the low level of discrimination among the possible installations and to rank each individual unit uniquely. The analysis is designed to guide property owners in identifying favorable solar photovoltaic investments within their portfolios under changing conditions.
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| 8. |
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| 9. |
- Belin, Matts-Åke, 1966-, et al.
(författare)
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Vision Zero : a road safety policy innovation
- 2012
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Ingår i: International Journal of Injury Control and Safety Promotion. - : Informa UK Limited. - 1745-7319 .- 1745-7300. ; 19:2, s. 171-179
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Tidskriftsartikel (refereegranskat)
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| 10. |
- Envall, Ida, et al.
(författare)
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What evidence exists related to soil retention of phosphorus from on-site wastewater treatment systems in boreal and temperate climate zones? : A systematic map protocol
- 2020
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Ingår i: Environmental Evidence. - : BMC. - 2047-2382. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- Background Soil-based on-site wastewater treatment systems (OWSs) are suspected to contribute to eutrophication of surface waters, due to the discharge of phosphorus (P). However, along the flow path between the facilities and surface waters, different processes contribute to delay the transport of phosphorus through the ground. This may reduce the unwanted impact on receiving water bodies. However, the strength and significance of this so-called soil retention remains unclear. In Sweden, there are nearly one million OWSs. To protect surface waters, a high P removal rate (up to 90%) is often required by the local municipalities. However, since these requirements may have costly consequences to property owners, it is debated as to whether they are too strict. In this debate, it is often claimed that the retention of P occurring in natural environments may be underestimated by authorities. Accordingly, there is a need for a scrutiny of the available evidence related to soil retention of phosphorus from OWSs. This is the objective of the planned systematic map. Focus will be on boreal and temperate climate zones. Methods Searches will be made for peer-reviewed articles and grey literature using bibliographic databases, search engines, specialist websites and stakeholder contacts. The references will be screened for relevance according to a predefined set of eligibility criteria. At stage one, after testing and clarifying the eligibility criteria, the references will be single-screened based on title and abstract. At stage two, potentially relevant references will be screened in full-text independently by two reviewers. We will compile a detailed database of the relevant studies. Moreover, a narrative report will be produced, describing the research landscape in general terms. This will be carried out with a conceptual model, describing the processes involved in P retention in natural environments, as a foundation. It will be discussed where the respective studies/study types fit into the conceptual model, and also evaluated how each study/study type can be related to the overarching question of eutrophication. Moreover, we will describe identified knowledge gaps that warrant further primary research effort, as well as identified knowledge clusters that could be suitable for systematic reviews.
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