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  • 1651.
    Nyström, Fredrik
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Nordqvist, Kerstin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Herrmann, Inga
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Hedström, Annelie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Removal of small particles from urban snow melt mixture by coagulation/flocculation and sedimentation2017In: 14th IWA/IAHR International Conference on Urban Drainage: Conference Proceedings, 2017, 2017Conference paper (Other academic)
    Abstract [en]

    This abstract presents a laboratory study of a coagulation/flocculation process on an urban snow melt mixture. Coagulation/flocculation is ubiquitous in water treatment, but has seen little use in the stormwater context. Using a jar-test procedure five different chemicals are evaluated as primary coagulants and their treatment performance on urban snow melt with respect to solids removal and metal content. Particle-size distribution measurements will indicate the process effect on different size fractions in the urban snow melt. Analysis for metal content will show the extent of metal reduction that occurs, either by separating out the particulate fraction or due to precipitation reactions.

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  • 1652.
    Nyström, Fredrik
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Nordqvist, Kerstin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Herrmann, Inga
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Hedström, Annelie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Treatment of road runoff by coagulation/flocculation and sedimentation2019In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 79, no 3, p. 518-525Article in journal (Refereed)
    Abstract [en]

    A laboratory investigation of the treatment potential of a coagulation process in the context of stormwater treatment was undertaken. The initial 25 L road runoff generated from four rain events was collected and subjected to a jar-testing regime with two commercial coagulants. The treatment effect was assessed by analysing the runoff before and after treatment for turbidity, suspended solids and metal content. The coagulation process resulted in particle and total metal reduction of more than 90% compared to 40% for only sedimentation. Up to 40% reduction of dissolved Cr, Cu and Pb was also observed compared to 0% for sedimentation. This study shows that coagulation may be a useful process for stormwater treatment systems when the treatment requirements are high.

  • 1653.
    Näslund, Arvid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Standardisering av stumsvetsning med PE-ledningar: I anläggningsprojekt2020Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Butt-welding is a method used when two PE wires are joined into a long chain of pipes that can then be used for a water pipeline. The method of butt-welding is a relatively new method and it started to become more common in the early1990s. Since then, the material PE has become the dominant material for water pipes, which has led to a bigger demand of butt-welding. Hence, the focus of this work is to contribute to a standardization of the whole process of butt-welding. The process extent from when the pipes come delivered to the pipes being fully welded. The reason why the whole process is considered in this work is that there are already predetermined parameters for the actual butt-welding. The parameters are for the finished weld joint to be considered correct and professional. The surrounding process is neither described nor standardized as it stands at present.

     

    Why the process of butt-welding is interesting and topical to study is because about 700 km of pipes are laid each year for an amount of SEK 2.8 billion, in Sweden alone. Thus, there is a benefit to standardizing and improving the process of butt-welding. The aim will be to study the possibilities for improvement with the butt-welding process

     

    The conclusions from this study are that, among other things, the butt-welding containers need to be improved, which can be achieved with the help of the tool 5S from the philosophy lean. Another improvement is to always use an WDP plan over the mute welding area to facilitate establishments and during the work. In addition, to succeed in standardization, there is a need for committed leadership in terms of encouraging the use of the standard and using the skills and experience available. By standardizing the butt-welding process from start to finish can both save time and money.

     

    This paper has separated itself from dimensions less than 200 mm and larger than 315 mm. Even though there are still many similarities in the process with smaller and larger pipes. The conclusions drawn in this work should therefore be generalized to be valid for all types of PE pipelines.

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  • 1654.
    Näslund, Olov
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    VA-system i omvandlingsområden - vad kostar de?2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    More and more people choose to live permanently in houses built as vacation houses, thereby creating transition areas. The increased occupancy in the houses tends to lead to larger water usage and often demands improved wastewater systems. There are three main ways in which this demand usually is met: each property builds an on-site system, the properties jointly build a facility through a community association, or the properties connect to the municipality’s network.

    The aim was to evaluate the costs of water and wastewater systems in transition areas in Sweden. This was done by studying five different improved transition areas and comparing the estimated costs with the actual cost of the systems. Both total investment costs and cost per property were calculated, as well as capital costs, and operation and maintenance costs. How the municipalities choose the sanitation system to be implemented was also a part of the study. 

    It was much more expensive for the municipality to build pipes than for a community association. One reason for this was shallower pipe placement. Another conclusion was that if part of a sanitation system already exists and is in good shape, this will lead to lower investment costs for a new system using that part. The operation costs for on-site systems on each property will be much higher for a family living there permanently, compared to that of a family living there only part time.

    Municipalities in Sweden generally do not compare different types of systems before deciding on an improved water and sanitation system in a transition area. Instead they almost always build a transmission line for water and wastewater to connect the area to an already existing centralized system. 

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  • 1655. Odhiambo, M.
    et al.
    Viñas, V.
    Sokolova, Ekaterina
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Pettersson, T. J. R.
    Health risks due to intrusion into the drinking water distribution network: hydraulic modelling and quantitative microbial risk assessment2023In: Environmental Science: Water Research & Technology, ISSN 2053-1400, E-ISSN 2053-1419, Vol. 9, no 6, p. 1701-1716Article in journal (Refereed)
    Abstract [en]

    Ageing water infrastructure is prone to increased physical deficiencies. These form pathways for pathogen intrusion into drinking water distribution networks (WDNs), hence posing major health risks to consumers. This study aimed at estimating the risk of infection from pipe breaks and intermittent water supply, which are some of the major causes of sustained low pressure within the WDN and hence the triggers for pathogen intrusion. Further, the effect of groundwater level on pathogen intrusion was investigated. Three risk scenarios were evaluated on the example of a real WDN in Sweden: (i) pipe break with no intrusion from leak holes, (ii) pipe break with intrusion due to leak holes, and (iii) insufficient water supply in the presence of leak holes. Pressure distribution from hydraulic modelling, estimated groundwater levels, and pathogen concentration in intruding water (from field study) were used to estimate the intrusion and the number of pathogens entering the WDN. Reference pathogens Campylobacter, Cryptosporidium, and norovirus were used in quantitative microbial risk assessment (QMRA) for assessing the health risks. Results indicated that the daily probability of infection exceeded an acceptable target value of 10−6 for most of the WDN and for all scenarios. The findings were consistent with the estimated annual burden of acute gastrointestinal illness in Sweden. The concentration of pathogens in intruding water and the duration of the low-pressure-causing event were observed to influence the probability of infection the most. The results from this study can be used to identify vulnerable sections in the WDN, which can be targeted for additional investment in monitoring and/or renewal.

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  • 1656.
    Okhravi, Amanda
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Evaluation of the suppressive effect of intermittent aeration on nitrite-oxidising bacteria in a mainstream nitritation-anammox process2015Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    An alternative to conventional removal of nitrogen through autotrophic nitrification and heterotrophic denitrification is autotrophic nitritation-anammox. The anammox bacteria oxidise ammonium directly to nitrogen gas with nitrite as an electron acceptor. Total autotrophic removal of nitrogen in the mainstream would bring wastewater treatment plants closer to being energy self-sufficient as it would allow for a significant reduction of aeration and an increased chemical oxygen demand reduction in the pre-treatment. An increased chemical oxygen demand reduction by mechanical treatment would potentially generate a greater biogas yield in the subsequent anaerobic digestion of the sludge.

    Nitritation-anammox processes have been successfully implemented over the world for treatment of ammonium rich sludge liquor of higher temperatures, while the feasibility of a mainstream implementation is still under evaluation. Lower ammonium concentrations, lower operating temperatures and better effluent quality represent the main challenges considering this energy autarkic treatment technique.

    Terminating nitrification at nitritation, i.e. favouring ammonia-oxidising bacteria while supressing nitrite-oxidising bacteria, is vital for a functioning nitritation-anammox process. This study aims to evaluate the suppressive effect of intermittent aeration on nitrite- oxidising bacteria while sustaining anammox activity by ex-situ batch tests in a pilot-scale moving bed biofilm reactor at Sjölunda Wastewater Treatment Plant in Malmö, Sweden. The pilot plant consists of one reactor treating sludge liquor and two mainstream reactors, connected in series, receiving effluent from a high-loaded activated sludge plant.

    The batch test showed a slight decrease of nitrite-oxidising bacteria activity when the reactors were intermittently aerated. Some loss in activity is expected as oxygen supply is decreased when aeration is switched from continuous to intermittent. Furthermore, the decrease coincided with an increased organic carbon loading favouring fast growing heterotrophic bacteria. The decrease in nitrite-oxidising bacteria activity can thereby be coupled with an increased competition for dissolved oxygen and space with heterotrophic bacteria.

    The suppression of nitrite-oxidising bacteria was not selective as results indicate a decrease in ammonia-oxidising bacteria activity as well. The nitrogen removal rate was decreased during the study while the potential anammox activity was stable in the mainstream and increased in the sludge liquor reactor. This indicates that the anammox bacteria are not hampered but rather that the availability of nitrite, i.e. the activity of ammonia-oxidising bacteria, is the limiting factor of the process. 

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  • 1657.
    Okoli, Kenechukwu
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. Uppsala University.
    The effect of model averaging versus model selection in design flood estimates – a case study for the Tiber River, in ItalyManuscript (preprint) (Other academic)
    Abstract [en]

    This study aims at comparing model averaging to model selection techniques in design flood estimation. Model selection refers to the selection of  a single best distribution function by means of a suitable selection criterion, such as, Akaike Information Criterion (AIC). Model averaging refers to the modelling approach where the estimates from a number of probability models are combined together as a weighted average. We investigated two methods of model averaging. First, weighted model averaging (WMA) were differential weights are assigned to estimates based on different distribution functions with the distribution when the best fit having the highest weight. Second, equal weighting or model mean (MM) which is similar to taking the arithmetic mean of design flood estimates from all the distributions considered. MS and MA (which includes WMA and MM) were implemented using an exceptionally long time series of annual maximum flows recorded at the Tiber River in Rome, Italy.  For this study, comparisons we refer to the 1-in-100 year flood, i.e. the quantile of annual maximum flows corresponding to a 1% exceedance probability, widely used as a reference in flood risk management. The results suggest that MA performs better than MS. Specifically, MM performs better that WMA even though the latter can be judged as to be consistent with logical reasoning.

  • 1658.
    Okoli, Kenechukwu
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Centre of Natural Hazards and Disaster Science (CNDS), Uppsala, Sweden.
    Breinl, Korbinian
    Centre of Natural Hazards and Disaster Science (CNDS), Uppsala, Sweden; Institute of Hydraulic Engineering and Water Resources Management, TU Vienna, Vienna, Austria.
    Mazzoleni, Maurizio
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. Centre of Natural Hazards and Disaster Science (CNDS), Uppsala, Sweden.
    Di Baldassarre, Giuliano
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Centre of Natural Hazards and Disaster Science (CNDS), Uppsala, Sweden.
    Design Flood Estimation: Exploring the Potentials and Limitations of Two Alternative Approaches2019In: Water, E-ISSN 2073-4441, Vol. 11, no 4, article id 729Article in journal (Refereed)
    Abstract [en]

    The design of flood defence structures requires the estimation of flood water levels corresponding to a given probability of exceedance, or return period. In river flood management, this estimation is often done by statistically analysing the frequency of flood discharge peaks. This typically requires three main steps. First, direct measurements of annual maximum water levels at a river cross-section are converted into annual maximum flows by using a rating curve. Second, a probability distribution function is fitted to these annual maximum flows to derive the design peak flow corresponding to a given return period. Third, the design peak flow is used as input to a hydraulic model to derive the corresponding design flood level. Each of these three steps is associated with significant uncertainty that affects the accuracy of estimated design flood levels. Here, we propose a simulation framework to compare this common approach (based on the frequency analysis of annual maximum flows) with an alternative approach based on the frequency analysis of annual maximum water levels. The rationale behind this study is that high water levels are directly measured, and they often come along with less uncertainty than river flows. While this alternative approach is common for storm surge and coastal flooding, the potential of this approach in the context of river flooding has not been sufficiently explored. Our framework is based on the generation of synthetic data to perform a numerical experiment and compare the accuracy and precision of estimated design flood levels based on either annual maximum river flows (common approach) or annual maximum water levels (alternative approach).

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  • 1659.
    Okoli, Kenechukwu
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Ctr Nat Hazards & Disaster Sci CNDS, Villavagen 16, S-75236 Uppsala, Sweden.
    Mazzoleni, Maurizio
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Ctr Nat Hazards & Disaster Sci CNDS, Villavagen 16, S-75236 Uppsala, Sweden.
    Breinl, Korbinian
    Ctr Nat Hazards & Disaster Sci CNDS, Villavagen 16, S-75236 Uppsala, Sweden; Tech Univ Wien, Inst Hydraul Engn & Water Resources Management, Karlspl 13-222, A-1040 Vienna, Austria.
    Di Baldassarre, Giuliano
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Ctr Nat Hazards & Disaster Sci CNDS, Villavagen 16, S-75236 Uppsala, Sweden.
    A systematic comparison of statistical and hydrological methods for design flood estimation2019In: Hydrology Research, ISSN 1998-9563, E-ISSN 2224-7955, Vol. 50, no 6, p. 1665-1678Article in journal (Refereed)
    Abstract [en]

    We compare statistical and hydrological methods to estimate design floods by proposing a framework based on virtual reality. To illustrate the framework, we used probability model selection and model averaging as statistical methods, while continuous simulations made with a simple or a perfect rainfall-runoff model are used as hydrological methods. The results of our numerical exercise show that design floods estimated by using a simple rainfall-runoff model have small parameter uncertainty and limited errors, even for high return periods. Statistical methods perform better than the linear reservoir model in terms of median errors for high return periods, but their uncertainty (i.e. variance of the error) is larger. Moreover, selecting the best fitting probability distribution is associated with numerous outliers. On the contrary, using multiple probability distributions, regardless of their capability in fitting the data, leads to significantly less outliers, while keeping a similar accuracy. Thus, we find that, among the statistical methods, model averaging is a better option than model selection. Our results also show the relevance of the precautionary principle in design flood estimation, and thus help develop general recommendations for practitioners and experts involved in flood risk reduction.

  • 1660.
    Okwori, Emmanuel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Analytics-driven approaches supporting asset management of sanitary sewer networks2024Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Sewer blockages can cause overflows and flooding, with consequences such as damage to property and environmental pollution, risks to public health and economic loss. Despite the causes being understood, blockages in sewer networks may occur unpredictably. The responsible staff for sewer networks at water utilities need to efficiently determine the most effective action (what), the specific network location needing attention (where), the optimal timing for intervention (when), and the appropriate remedial task (how), especially given the unpredictability of blockages. Today a reactive approach to asset management and maintenance is often adopted. Additionally, data availability, quality and interoperability between systems are not always at levels that can support decided objectives, proactive maintenance planning and asset management of pipe networks. Thus, the aim of this thesis is to propose and evaluate approaches that can support analytics-driven maintenance planning and asset management for sewer networks. These approaches aim to contribute to mitigating the impact of siloed data structures and enhance the understanding of blockage root causes from a spatial perspective.

    In this thesis, the challenges of data management in the asset management of pipe networks were investigated through focus group workshops and questionnaire surveys. A conceptual framework was developed based on findings from focus group workshops and surveys. The framework combines data quality assessments, interoperability evaluations between asset management tools, data collection, and informational benefits analysis. This framework aimed to identify the presence of data silos and plausible pathways towards more data-driven data management strategies. A performance assessment combining performance indicators associated with blockages and partial least squares regression (PLS) was conducted to draw inferences that could be useful at a strategic level. Furthermore, a spatial heterogeneity assessment of blockages and factors affecting blockages was carried out. This approach combined network kernel density estimation (NKDE), network k-function, and geographically weighted Poisson regression (GWPR). Lastly, a vulnerability assessment was carried out that combined topological analysis using edge-based centrality measures and network cross-k-function. These approaches were applied to three sewer networks.

    The focus group workshops and questionnaire surveys identified several challenges affecting data management in the context of pipe network asset management. Many of the challenges could be ascribed to issues related to data quality and interoperability. Results from the preliminary application of the conceptual framework showed how it could be applied for identifying data silos and pathways to data-driven decision-making towards proactive management blockages in sewers. The observed spatial trends and patterns from network k-function analysis and network kernel density estimation showed spatial variability in the occurrence of blockages (single occurring and recurring). Geographically-weighted Poisson regression analysis showed spatial heterogeneity in factors influencing blockage propensity. The network cross-k-function analysis demonstrated that pipes with historical blockage incidents tend to be clustered around critical pipes with higher centrality values. These results could support vulnerability assessments in sewer networks and the development of targeted maintenance strategies. These approaches together could aid data-informed maintenance planning and asset management at the strategic, tactical and operational levels.

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  • 1661.
    Okwori, Emmanuel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Data-driven approaches for proactive maintenance planning of sewer blockage management2021Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Blockages have been reported to account for a significant proportion of reported failures in sewer networks. The malfunctioning of the sewer network from blockages and the subsequent disruption to other public services and flooding may constitute a risk to the environment and human health. Due to the complex nature of underground sewer networks, a reactive approach to blockage maintenance is typically employed. However, although proactive maintenance strategies have been developed, both approaches could be expensive and highlight the need to address the problem with analytics-based methods. Although blockage triggering mechanisms may be known, sewer blockages often appear at random. Thus, it is necessary to improve the understanding of the influential mechanisms involved in forming blockages in sewer networks to support its maintenance and guarantee adequate performance levels. The overall aim of this thesis was to contribute with new knowledge, approaches and methods that can support improved proactive maintenance planning of blockages in sewer networks.

    Various methods to achieve the aim have been investigated in relation to asset management planning levels. At the strategic level, blockages and associated performance indicators were employed in conjunction with Poisson and partial least squares regression to assess the performance of sewer networks, including gaining additional insights. At the tactical and operational levels, a procedure was developed. The procedure combines network k-function, geographically weighted regression and random forest ensembles. The network k-function analysis explains the significance of the spatial variation of blockages. The Geographically weighted Poisson regression (GWPR) investigates the degree of influence of explanatory factors on increased blockage propensity in differentiated segments of the sewer networks. Thirdly, the random forest ensembles was used to predict pipes with blockage recurrence likelihood. A proposed conceptual framework was applied at all asset management levels to assess the state of data-driven integrated asset management (IAM), based on data quality assessments, interoperability evaluations between IAM tools, and data collection and informational benefits analysis. 

    Results from demonstrating the methods with data from the Swedish waters statistical database and three Swedish municipal sewer networks, namely A, B and C, are presented. Blockage related performance indicators showed that the average blockage rate in medium sized networks was 2-3 times the rate in other sewer networks in Sweden. Furthermore, sewer maintenance strategies were suspected to be ineffective, and increased proactive strategies may improve maintenance efficiency. The procedure in networks A, B and C indicated that the clustering of recurrent blockages maybe linked to an increased need for flushing-related maintenance in sewer pipe networks. The degree of influence between investigated factors and increased blockage propensity indicated that these relationships were not global (not the same in all locations) within and between the sewer networks for networks A, B and C. These non-stationary relationships were observed to occur in various forms, i.e. adequate self-cleaning velocity showed positive and negative correlations in different locations. The networks with relatively more substantial spatial clusters of blockages, higher data quality and availability were observed to have a higher mean prediction accuracy. The applied conceptual framework showed that intuitive asset management characterised the current state of blockage management in the municipal sewer network C with medium to good data quality and low interoperability.

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  • 1662.
    Okwori, Emmanuel
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Pericault, Youen
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Ugarelli, Rita
    SINTEF Community, SINTEF AS, 0373 Oslo, Norway.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Hedström, Annelie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Data-driven asset management in urban water pipe networks: a proposed conceptual framework2021In: Journal of Hydroinformatics, ISSN 1464-7141, E-ISSN 1465-1734, Vol. 23, no 5, p. 1014-1029Article in journal (Refereed)
    Abstract [en]

    Analytical tools used in infrastructure asset management of urban water pipe networks are reliant on asset data. Traditionally, data required by analytical tools has not been collected by most water utilities because it has not been needed. The data that is collected might be characterised by low availability, integrity and consistency. A process is required to support water utilities in assessing the accuracy and completeness of their current data management approach and defining improvement pathways in relation to their objectives. This study proposes a framework to enable increased data-driven asset management in pipe networks. The theoretical basis of the framework was a literature review of data management for pipe network asset management and its link to the coherence of set objectives. A survey to identify the current state of data management practice and challenges of asset management implementation in five Swedish water utilities and three focus group workshops with the same utilities was carried out. The main findings of this research were that the quality of pipe network datasets and lack of interoperability between asset management tools was a driver for creating data silos between asset management levels, which may hinder the implementation of data-driven asset management. Furthermore, these findings formed the basis for the proposed conceptual framework. The suggested framework aims to support the selection, development and adoption of improvement pathways to enable increased data-driven asset management in municipal pipe networks. Results from a preliminary application of the proposed framework are also presented.

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  • 1663.
    Okwori, Emmanuel
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Hedström, Annelie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Data integration in asset management of municipal pipe networks in Sweden: Challenges, gaps, and potential drivers2024In: Utilities Policy, ISSN 0957-1787, E-ISSN 1878-4356, Vol. 86, article id 101689Article in journal (Refereed)
    Abstract [en]

    This study involved a survey of Swedish water utilities to evaluate their pipe-network data-collection objectives, usage, storage, and exchange routines. Factors impacting data integration (and the associated benefits) were also identified. Results showed that current data storage and exchange routines can be augmented to support commonly identified objectives and data utilisation needs, especially in larger water utilities. Levels of awareness of the opportunities for and benefits gained through asset management processes and data integration varied between utilities. Further research on the benefits of data integration in pipe network asset management is required to develop an evidence base on benefits accrued in practice, especially considering metadata, the diversity of legacy systems still in operation, costs and policy use.

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  • 1664.
    Okwori, Emmanuel
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Hedström, Annelie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Edge-based graph centrality measures with spatial analytics to support vulnerability assessment and maintenance planning in sewer networksManuscript (preprint) (Other academic)
  • 1665.
    Okwori, Emmanuel
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Hedström, Annelie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Performance assessment of Swedish sewer pipe networks using pipe blockage and other associated performance indicators2019Conference paper (Refereed)
    Abstract [en]

    Sewer networks are expected to operate with minimal or no interruptions. The complex nature of randomly occurring failures in sewer networks arising from blockages significantly adds to the cost of operation and maintenance. Blockages are significant due to sewage backup or basements flooding, resulting from their occurrence. Continuous performance assessment of sewer pipe networks is necessary to ensure a required level of service at an acceptable cost. This study provides insight into the performance of the sewer pipe networks by assessing the proneness of the network to blockages and drawing inferences at a holistic strategic level of influential explanatory factors of blockage proneness, using data available in the VASS statistics database managed by Swedish Water and Wastewater Association. Results indicate that medium sized municipalities are prone to at least 30% more blockages per km per year compared to other municipalities. A hypothesis of explanatory factors includes, reduced flow volumes and design flow depth resulting in flow velocities below self-cleaning velocity in sewer pipe networks encouraging the sluggishness of flow and increased possibility for sediment deposition and accumulation in sewer leading to blockages. This is also exacerbated by the deposition of non-disposables (wet wipes, baby diapers, hard paper etc.), accumulation of FOGs in sewers and increased water conservation measures. Blockages also show a trend indicating occurrence may have a constant return frequency in medium – less than small sized municipalities.

  • 1666.
    Okwori, Emmanuel
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Hedström, Annelie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Performance assessment of Swedish sewer pipe networks using pipe blockage and other associated performance indicators2020In: H2Open Journal, E-ISSN 2616-6518, Vol. 3, no 1, p. 46-57Article in journal (Refereed)
    Abstract [en]

    Sewer pipe networks are expected to operate with minimal or no interruptions. The complex nature of randomlyoccurring failures in sewer networks arising from blockages significantly adds to the cost of operation and maintenance.Blockages are significant due to sewage backup or basements flooding, resulting from theiroccurrence. Therefore, continuous performance assessment of sewer pipe networks is necessary to ensurerequired levels of service at an acceptable cost. This study provides insight into the performance of the sewerpipe networks by assessing the proneness of the network to blockages. Furthermore it draws inferences at a holisticstrategic level of influential explanatory factors of blockage proneness, using data available in the SwedishWater and Wastewater Association’s benchmarking system. Results indicate that medium sized municipalitiesare prone to at least 30% more blockages per km per year compared to other municipalities. A hypothesis ofexplanatory factors includes reduced flow volumes and flow depth. Flow velocities below self-cleaning velocityin sewer pipe networks, encouraged by sluggishness of flow are responsible for increased possibility for sedimentdeposition and accumulation in sewers leading to blockages. This is also exacerbated by the deposition of nondisposables(wet wipes, baby diapers, hard paper, etc.), accumulation of fats, oils and grease in sewers andincreased water conservation measures.

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  • 1667.
    Okwori, Emmanuel
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Hedström, Annelie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Spatial heterogeneity assessment of factors affecting sewer pipe blockages and predictions2021In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 194, article id 116934Article in journal (Refereed)
    Abstract [en]

    Efficient management of sewer blockages requires increased preventive maintenance planning. Conventional approaches to the management of blockages in sewer pipe networks constitute largely unplanned maintenance stemming from a lack of adequate information and diagnosis of blockage causative mechanisms. This study mainly investigated a spatial statistical approach to determine the influence of explanatory factors on increased blockage propensity in sewers based on spatial heterogeneity. The approach consisted of the network K-function analysis, which provided an understanding of the significance of the spatial variation of blockages. A geographically-weighted Poisson regression then showed the degree of influence that explanatory factors had on increased blockage propensity in differentiated segments of the sewer pipe network. Lastly, blockage recurrence predictions were carried out with Random Forest ensembles. This approach was applied to three municipalities. Explanatory factors such as material type, number of service connections, self-cleaning velocity, sagging pipes, root intrusion risk, closed-circuit television inspection grade and distance to restaurants showed significant spatial heterogeneity and varying impacts on blockage propensity. The Random Forest ensemble predicted blockage recurrence with 60–80% accuracy for data from two municipalities and below 50% for the last. This approach provides knowledge that supports proactive maintenance planning in the management of blockages in sewer pipe networks.

  • 1668.
    Okwori, Emmanuel
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Hedström, Annelie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Using centrality measures, network cross k-function and geographically weighted regression as decision support for operational issues and redesigning sewers.2022In: 10th International Conference on Sewer Processes and Networks, 2022Conference paper (Refereed)
    Abstract [en]

    The topology of Sanitary Sewer Networks (SSNs) can play an influential role in the occurrence and magnitude of operational failures such as blockages and basements flooding (Reyes-Silva et al., 2020). For example, meshed (grid-like) topologies are reported to be less vulnerable to failures compared to branched (tree-like) topologies (Zhang et al., 2017). However, in reality, most SSNs are reported to have a predominantly branched topology (Reyes-Silva et al., 2020). Therefore, it could be argued that the spatial behaviour of operational failures may be related to the topological properties of SSNs. This study explored this argument by investigating the spatial association between the location of recurrent blockages and the location of influential nodes within the network. Graph theory–centrality measures (Ganesan et al., 2020) and the network cross-K-function (Okabe and Sugihara, 2012) were the methods used. Secondly, the question of which structural, hydraulic or environmental factors may explain the identified spatial associations was also explored using geographically weighted regression (Fotheringham and Charlton, 2009). In lieu of robust properly calibrated hydraulic models, results from centrality measures and network cross k-function can support the discovery of influential locations within the topology of SSNs that may propagate recurrent blockages. Such influential locations may also be inception points for remedial actions such as redesigning, which may be more cost-effective in the long term compared to conventional approaches like flushing. Results from a preliminary application of centrality measures and network cross-function to the SSN of one municipality (total network length 500 km, ≈40 people/km) using its historical blockage data are presented.

  • 1669.
    Olofsson, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Climate change and urban drainage: future precipitation and hydraulic impact2007Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Increasing global mean temperature influences the hydrologic cycle. In the 21st century, hydrologic change featuring more heavy precipitation events is very likely according to the UN Intergovernmental Panel on Climate Change, IPCC. This change will have a great impact on urban environments and infrastructures. In Sweden, precipitation during the winter will most likely increase by as much as 30 to 50 % by the end of the 21st century, while summer precipitation will decrease in the southern and middle parts of Sweden. Recent years have seen a number of floods caused by heavy rainfalls. With climate change, the problem with floods can be expected to continue and increase. To prevent adverse damage, modelling how the changes in precipitation and temperature will influence the urban drainage systems and how measures can be taken to prevent or reduce the consequences of floods has become increasingly important. The main objective with this thesis is to investigate the hydraulic impact in an urban drainage system due to the presumed increase in intense rainfalls. Regional Climate models produce temperature and precipitation data for the future. The regional climate model RCA3 from Rossby Center at SMHI, produces data with a spatial resolution of 50*50 km and a temporal resolution of 30 min. To be able to use the climate data in urban drainage models, temporal and spatial resolution must be improved. A modification of the so-called Delta change method, where the changes are related to the rainfall intensity level, is presented to transfer the changes in rain characteristics from different future time periods to an observed series. For the study area, the climate model shows an increase of the highest intensities of up to 20 % for the 21st century. Effects of these changes are studied on an urban drainage system in the study area. Results from the urban drainage simulations show that higher water flow- ratios in pipes, longer durations of floods, and more frequent floods can be expected if the climate continues to change with more high intensity rains, as the climate models predict. The maximum water levels in nodes were significantly higher for all future time periods that were simulated. Even in the near future (2011-2040), maximum water levels in nodes were >0,1 m higher compared to today's climate. Since the renewal rate of pipes in the existing urban drainage system is relatively slow, emphasis must not lie only on city development but also on future climate change. Design criteria, therefore, need to be changed according to changes in precipitation. Weak spots in the system must be identified for the adaptation to be as effective as possible. Knowing when, where, and how to put the correct measures when adapting the urban drainage system is essential for efficient management. Climate change also affects urban drainage in different ways, depending on where in Sweden the city lies. In northern Sweden, problems can arise with changing snowmelt patterns, for example. Further research involves an analysis of the consequences that higher water levels, increased max flow, and higher seasonal variations will have and of the adaptation strategies required not only for the urban drainage systems but also for other infrastructures.

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  • 1670.
    Olofsson, Mats
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Olsson, Jonas
    SMHI.
    Berggren, Karolina
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Adaptation of RCA3 climate model data for the specific needs of urban hydrology simulations2006In: Extreme Precipitation, Multisource Data Measurement and Uncertainty: Proceedings of the 7th International workshop on precipitation in urban areas / [ed] Peter Molnar, Zürich: Institute of Environmental Engineering, ETH, Zürich , 2006, p. 144-148Conference paper (Refereed)
    Abstract [en]

    Adapting climate model data to urban drainage applications can be done in several ways but a popular way is the so-called ‘delta change' method. In this method, relative changes in rainfall characteristics estimated from climate model output are transferred to an observed rainfall time series, generally by multiplicative factors. In this paper, a version of the method is proposed in which these ‘delta factors' are related to the rainfall intensity level. This is achieved by calculating changes in the probability distribution of rainfall intensities and modelling the delta factors as a function of percentile. The model is applied to 30-min output from the RCA3 regional atmospheric climate model, in a grid box covering Kalmar City, Sweden. The climate model results indicate an increase of the highest intensities by up to ~20% and a decrease of lower intensities by up to almost 40%. This result is valid for a 30-min time scale, and to evaluate whether urban drainage impact assessment can be meaningfully performed on this time scale, a MOUSE model was applied in Kalmar using different time steps. The results indicate that a 30-min time step may be meaningful, but that ways to transfer the rainfall changes also to data of a higher time resolution needs to be considered. This will be done in future studies, as well as further testing and evaluation for other Swedish cities.

  • 1671.
    Olsenius, Björn
    et al.
    Jönköping University, School of Engineering, JTH, Civil Engineering and Lighting Science.
    Tornell, Mattias
    Jönköping University, School of Engineering, JTH, Civil Engineering and Lighting Science.
    Undersökning av en teknisk lösning för att minska risken för översvämning i lågstråk i en urban miljö vid större nederbörd2021Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Purpose: In many cities there are areas that are lower than the surrounding terrain (low-lying areas). In these low-lying areas, there is a great risk that stormwater will accumu-late in the event of heavy rainfall and cause floods and damage to buildings and facili-ties. In this study, a review has been carried out of various theories, methods and appli-cations that can form the basis for a technical solution to solve the problem of flood risk in an urban environment with low-lying areas.

    Method: First, a literature study was conducted to, among other things, deepen the knowledge of the subject. Subsequently, four interviews were conducted where the goal was to utilize the knowledge that experts have about which technical solutions are suit-able in an urban environment and what costs different stormwater facilities have. The last step was to carry out a case study where a selected solution was studied with the aim of investigating the suitability of constructing that solution.

    Findings: The interviews showed that there are many parameters to take into account when designing and building stormwater facilities that are effective in the event of a downpour. Open solutions such as flood surfaces and ditches / canals were preferred as they were partly more efficient and partly because they were often cheaper to construct. The literature study also gave similar results, but there was greater variation in which solutions were suitable. The case study showed that the proposed solution could swal-low up to 60% of the precipitation in a 30-year rain but in the worst case only 16% of a 100-year rain.

    Implications: Judging by the results, the proposed solution was not sufficient to solve the flood problem in the event of a 100-year rain, which was the return time that Växjö municipality has the biggest problem with. To handle the large amount of precipitation, very large magazine volumes or many small solutions are needed in order for an ac-cepted level to be achieved, which the solution that was tested could not achieve. In the interviews, it also emerged that this was often the problem, which is basically due to too little available space and too much hardened surface. The recommendation will be to supplement with several other solutions or to install so-called cassettes under the street to increase storage capacity.

    Limitations: The result is limited by the fact that it is site-specific and thus more diffi-cult to apply in other locations. Since interviews have been conducted in several differ-ent municipalities, however, this aspect has diminished somewhat as many different opinions have been noted and presented. The calculations performed were not through a data modelling, which could possibly affect the reliability somewhat, even though according to the literature it was considered to maintain a sufficient level to be able to be used on smaller areas.

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    Undersökning av en teknisk lösning för att minska risken för översvämning i lågstråk i en urban miljö vid större nederbörd
  • 1672.
    Olsson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Natural Resources and Sustainable Development.
    Water use in the Chinese coal industry2015Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Freshwater resources are getting increasingly scarce throughout the world. In 21th century China, coal is the fuel of the nation’s economic growth. Coal is also the nation’s largest source of industrial water use. The objective of this thesis is to project water use in the Chinese coal industry up until 2035 by presenting two scenarios simulating two different approaches to water management policies.Literature studies makes up the base for estimating water use in three stages in the coal’s life cycle; mining, washing, and combustion. Through univariate sensitivity analysis, significant parameters are identified and included in the scenario modeling. Key for the study is the separation of water withdrawal rates and water consumption rates.The results indicate that future coal production and electricity demand have strong influence on water consumption. The coal industry’s water consumption is expected to have increased by 18-28% by 2035 depending on water use policies. By 2035, a business-as-usual scenario (BAU) will have increased annual water consumption by 24-63% from current levels, compared to an increase of 6-35% in a water saving scenario (WS). In terms of water withdrawal by 2035, the results show a 18-47% increase in the BAU scenario and a 9% decrease to 13% increase in the WS scenario. It is concluded that water management has high potential in mitigating and reducing water withdrawal rates, but failure to do so may result in a significant increase.

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  • 1673.
    Olsson, J.
    et al.
    Research and Development (hydrology), Swedish Meteorological and Hydrological Institute, Norrköping.
    Berggren, Karolina
    Olofsson, Mats
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Applying climate model precipitation scenarios for urban hydrological assessment: a case study in Kalmar City, Sweden2009In: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895, Vol. 62, no 3, p. 364-375Article in journal (Refereed)
    Abstract [en]

    There is growing interest in the impact of climate change on urban hydrological processes. Such assessment may be based on the precipitation output from climate models. To date, the model resolution in both time and space has been too low for proper assessment, but at least in time the resolution of available model output is approaching urban scales. In this paper, 30-min precipitation from a model grid box covering Kalmar City, Sweden, is compared with high-resolution (tipping-bucket) observations from a gauge in Kalmar. The model is found to overestimate the frequency of low rainfall intensities, and therefore the total volume, but reasonably well reproduce the highest intensities. Adapting climate model data to urban drainage applications can be done in several ways but a popular way is the so-called Delta Change (DC) method. In this method, relative changes in rainfall characteristics estimated from climate model output are transferred to an observed rainfall time series, generally by multiplicative factors. In this paper, a version of the method is proposed in which these DC factors (DCFs) are related to the rainfall intensity level. This is achieved by calculating changes in the probability distribution of rainfall intensities and modelling the DCFs as a function of percentile. Applying this method in Kalmar indicated that in summer and autumn, high intensities will increase by 20-60% by year 2100, whereas low intensities remain stable or decrease. In winter and spring, generally all intensity levels increase similarly. The results were transferred to the observed time series by varying the volume of the tipping bucket to reflect the estimated intensity changes on a 30-min time scale. In an evaluation of the transformed data at a higher 5-min resolution, effects on the intensity distribution as well as single precipitation events were demonstrated. In particular, qualitatively different changes in peak intensity and total volume are attainable, which is required in light of expected future changes of the precipitation process and a step forward as compared with simpler DC approaches. Using the DC transformed data as input in urban drainage simulations for a catchment in Kalmar indicated an increase of the number of surface floods by 20-45% during this century.

  • 1674.
    Olsson, Jesper
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Forkman, T.
    Swedish University of Agricultural Sciences, Sweden.
    Gentili, F.G.
    Swedish University of Agricultural Sciences, Sweden.
    Zambrano, Jesús
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Schwede, Sebastian
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Anaerobic co-digestion of sludge and microalgae grown inmunicipal wastewater: A feasibility study2018In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 77, no 3, p. 682-694Article in journal (Refereed)
    Abstract [en]

    In this study a natural mix of microalgae grown in wastewater of municipal character was co-digested with sewage sludge in mesophilic conditions, in both batch and semi-continuous modes. The semicontinuous experiment was divided into two periods with OLR 1 (Organic Loading Rate) of 2.4 kg VS m3 d-1 and HRT1 (Hydraulic Retention Time) of 15 days, and OLR2 of 3.5 kg VS m3 d-1 and HRT2 of 10 days respectively. Results showed stable conditions during both periods. The methane yield was reduced when adding microalgae (from 200 ± 25 NmL CH4 g VSin-1 , to 168±22 NmL CH4 g VSin-1). VS reduction was also decreased by 51%. This low digestability was confirmed in the anaerobic batch test. However, adding microalgae improved the dewaterability of the digested sludge. The high heavy metals content in the microalgae resulted in a high heavy metals content in the digestate, making it more difficult to reuse the digestate as fertilizer on arable land. The heavy metals are thought to originate from the flue gas used as a CO2 source during the microalgae cultivation. Therefore the implementation of CO2 mitigation via algal cultivation requires careful consideration regarding thesource of the CO2-rich gas.

  • 1675.
    Olsson, Jesper
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Schwede, Sebastian
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Microalgae as biological treatment for municipal wastewater - Effects on the sludge handling in a treatment plant2018In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, ISSN 0273-1223, Vol. 78, no 3, p. 644-654Article in journal (Refereed)
    Abstract [en]

    A mix of microalgae and bacteria was cultivated on pre-sedimented municipal wastewater in a continuous operated microalgae-activated sludge process. The excess material from the process was co-digested with primary sludge in mesophilic and thermophilic conditions in semi-continuous mode (5 L digesters). Two reference digesters (5 L digesters) fed with waste-activated sludge (WAS) and primary sludge were operated in parallel. The methane yield was slightly reduced (≈10%) when the microalgal-bacterial substrate was used in place of the WAS in thermophilic conditions, but remained approximately similar in mesophilic conditions. The uptake of heavy metals was higher with the microalgal-bacterial substrate in comparison to the WAS, which resulted in higher levels of heavy metals in the digestates. The addition of microalgal-bacterial substrate enhanced the dewaterability in thermophilic conditions. Finally, excess heat can be recovered in both mesophilic and thermophilic conditions. 

  • 1676.
    Olsson, John
    Kristianstad University, School of Teacher Education.
    Förbättrad vattenanvändning på Björnekulla Fruktindustrier AB: för ökad lönsamhet och bättre miljö2010Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Björnekulla Fruktindustrier AB i Åstorp vill minska kostnaderna för sin vattenförbrukning i fabriken. Det är endast en liten del av den totala vattenkonsumtionen som hamnar i slutprodukten. Majoriteten av vattnet går åt för tvättning av råvaror och maskinell utrustning. Anledningen till att kostnaderna är höga är den stora andel kommunalt vatten som fabriken köper in. För att minskaden andelen har jag undersökt två alternativ, ett eget reningsverk för återanvändning av vatten och en ny vattentäkt. För att undersöka möjligheten för ett reningsverk har jag analyserat det aktuella vattnet och sorterat ut de ämnen och parametrar som är utanför gränsvärden. Lämpliga reningssteg för att reducera och korrigera dessa parametrar har dimensionerats och sats ihop till ett komplett reningsverk. Att anlägga en ny vattentäkt och tillföra fabriken rent grundvatten är ett enkelt alternativ för att minska kostnaderna. Geologiskt ligger dock fabriken i ett svårt område och det kan vara svårt att hitta tillräcklig mängd vatten.

    Resultatet är ett förslag som kommer minska fabrikens kostnader avsevärt.

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    Förbättrad vattenanvändning på
  • 1677.
    Olsson, Jonas
    et al.
    Research and Development (hydrology), Swedish Meteorological and Hydrological Institute, Norrköping, Sweden.
    Arheimer, Berit
    Research and Development (hydrology), Swedish Meteorological and Hydrological Institute, Norrköping, Sweden.
    Borris, Matthias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Donnelly, Chantal
    Research and Development (hydrology), Swedish Meteorological and Hydrological Institute, Norrköping, Sweden.
    Foster, Kean
    Research and Development (hydrology), Swedish Meteorological and Hydrological Institute, Norrköping, Sweden.
    Nikulin, Grigory
    Rossby Centre, Swedish Meteorological and Hydrological Institute, Norrköping, Sweden.
    Persson, Magnus
    Department of Water Resources Engineering, Lund University, Box 118, Lund, Sweden.
    Perttu, Anna-Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Uvo, Cintia B.
    Department of Water Resources Engineering, Lund University, Box 118, Lund, Sweden.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Yang, Wei
    Research and Development (hydrology), Swedish Meteorological and Hydrological Institute, Norrköping, Sweden.
    Hydrological climate change impact assessment at small and large scales: Key messages from recent progress in Sweden2016In: Climate, E-ISSN 2225-1154, Vol. 4, no 3, article id 39Article, review/survey (Refereed)
    Abstract [en]

    Hydrological climate change impact assessment is generally performed by following a sequence of steps from global and regional climate modelling, through data tailoring (bias-adjustment and downscaling) and hydrological modelling, to analysis and impact assessment. This "climate-hydrology-assessment chain" has been developed with a primary focus on applicability to a medium-sized rural basin, which has been and still is the main type of domain investigated in this context. However, impact assessment is to an increasing degree being performed at scales smaller or larger than the medium-sized rural basin. Small-scale assessment includes e.g., impacts on solute transport and urban hydrology and large-scale assessment includes e.g., climate teleconnections and continental modelling. In both cases, additional complexity is introduced in the process and additional demands are placed on all components involved, i.e., climate and hydrology models, tailoring methods, assessment principles, and tools. In this paper we provide an overview of recent progress with respect to small- and large-scale hydrological climate change impact assessment. In addition, we wish to highlight some key issues that emerged as a consequence of the scale and that need further attention from now on. While we mainly use examples from work performed in Europe for illustration, the progress generally reflects the overall state of the art and the issues considered are of a generic character.

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  • 1678.
    Olsson, Oscar
    Umeå University, Faculty of Science and Technology, Umeå Institute of Design.
    SC Vega: Den fjärrstyrda räddningsfarkosten2021Independent thesis Basic level (degree of Bachelor of Fine Arts), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Swedish Sea Rescue Society (SSRS) is a voluntary organization that is responsible for the majority of all sea rescue missions in Sweden. In the past year, the organization has received an increased number of mission as a result of, among other things, more Swedes choosing to celebrate summers at home in Sweden.My thesis revolves around how to use modern technology in order to design a remotely controlled rescue vessel that can facilitate the Swedish Sea Rescue Society during less urgent missions, so-called membership missions, or preventive rescue missions as they are also called. These missions make up the majority of the organizations missions. The project has been carried out in collaboration with the Swedish Sea Rescue Society and has followed a classic design methodology based on research and interviews with people who touch on the chosen problem area, in order to give the project a relevant and solid foundation.

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    Oscar Olsson SC Vega Rapport 2021
  • 1679.
    Olsson, Peter
    Luleå University of Technology.
    Influence of ice-cover on local scour at circular bridge piers: an experimental study2000Licentiate thesis, monograph (Other academic)
    Abstract [en]

    The objective of this work has been to investigate the effect of a simulated ice cover on the local scour depth around a cylindrical pier. Experiments were performed in a laboratory flume for different flow velocities with both a smooth and rough cover. The bed material consisted of uniform ripple-forming sand. The experiments took place at the Hydraulic Laboratory of Clarkson University, USA. Comparisons were made with scour at free surface flow; the emphasis being on conditions with sediment transport on the bed, so called live bed conditions. The scour depth was continuously measured during each test and the result was presented as an average scour depth. A total of 30 test-series were made, 20 with a cover and 10 without. Two kinds of covers were used, smooth and rough. The experiments included both clear water conditions, i.e. no sediment transport, and live bed conditions. The results show that an ice-cover may increase the local scour depth by as much as 25-35%, or 0.3-0.5 pier diameters, at live bed conditions. The results in summary were: Covered tests gave larger scour depths for all flow velocities. These included both clear water scour and live bed scour. The difference in scour depth (between covered and free surface flow) was most pronounced for five bed conditions and most noticeable at relative flow velocities between 1.5 and 2. There the covered tests gave up to 35% larger scour depths, which in this range is equal to 0.5 pier diameters. The rough cover gave slightly larger scour depths than the smooth cover. The variation in scour depth during testing was larger for covered flow than free surface flow with approximate relative velocities between 1.8 to 3. At other velocities the variations were similar. The scour depths velocity-dependence and magnitude for free surface flow were in agreement with the findings of Melville (1984). The increased scour depth at clear water conditions, with covered flow, was in agreement with the findings of Bacuta and Dargahi (1986). The velocity-dependence of the scour depth followed a similar pattern for both covered and free surface flow conditions.

  • 1680.
    Olsson, Peter
    et al.
    Luleå University of Technology.
    Sellgren, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Energieffektiv gruvluftuppvärmning: preliminär problemanalys med utvecklingsförslag1991Report (Other academic)
  • 1681.
    Olsson, Peter
    et al.
    Luleå University of Technology.
    Sellgren, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Vattetrycksreglerade frysskyddsanordningar: översiktlig funktionsstudie1992Report (Other academic)
  • 1682.
    Olsson, Ulf
    Luleå University of Technology.
    Snow removal from streets and roads: an analysis of cost dependence and a discussion of engineer's possibilities for influencing productivity development1989Report (Other academic)
  • 1683.
    Olsthoorn, Bart
    et al.
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. Stockholm Univ, Hannes Alfvens Vag 12, S-11421 Stockholm, Sweden..
    Ronnqvist, Tryggve
    Radonova Labs AB, Rapsgatan 25, S-75450 Uppsala, Sweden..
    Lau, Cheuk
    Swedish Radiat Safety Author, Katrineholm, Sweden..
    Rajasekaran, Sanguthevar
    Univ Connecticut, Dept Comp Sci & Engn, Storrs, CT 06269 USA..
    Persson, Tomas
    Swedish Radiat Safety Author, Katrineholm, Sweden..
    Månsson, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Balatsky, Alexander V.
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. Stockholm Univ, Hannes Alfvens Vag 12, S-11421 Stockholm, Sweden.;Univ Connecticut, Dept Phys, Storrs, CT 06269 USA.;Univ Connecticut, Inst Mat Sci, Storrs, CT 06269 USA..
    Indoor radon exposure and its correlation with the radiometric map of uranium in Sweden2022In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 811, article id 151406Article in journal (Refereed)
    Abstract [en]

    Indoor radon concentrations are controlled by both human factors and geological factors. It is important to separate the anthropogenic and geogenic contributions. We show that there is a positive correlation between the radiometric map of uranium in the ground and the measured radon in the household in Sweden. A map of gamma radiation is used to obtain an equivalent uranium concentration (ppm eU) for each postcode area. The aggregated uranium content is compared to the yearly average indoor radon concentration for different types of houses. Interestingly, modern households show reduced radon concentrations even in postcode areas with high average uranium concentrations. This shows that modern construction is effective at reducing the correlation with background uranium concentrations and minimizing the health risk associated with radon exposure. These correlations and predictive housing parameters could assist in monitoring higher risk areas.

  • 1684.
    Oskarsson, Joakim
    et al.
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Olsson, Johan
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Bergkylsystemets påverkan på processen: En utvärdering och energieffektivisering på bergkylsystemet hos More biogas i Läckeby2021Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The work is based on a cooling plant installed at a biogas company, which was initially intended as a pilot project but is now fully used in the plant. It is not evaluated or documented and how much power is transmitted is unknown. The meaning of the work is to find out the effect and document the system in the form of both calculations, drawing and any areas of efficiency. Calculation was made via enthalpy the difference that was taken out over the heat exchangers involved, as well as the flow that was taken out via a control valve with the help of a measuring instrument. Drawing was made via the Visio program based on the facility's current design. The result for the cooling power that was transferred was calculated via flow and enthalpy, where the result was 14.03 kW over both heat exchangers. Calculation of what a potential improvement of insulation of the pipe system could contribute, based on the calculations, the energy savings could be doubled compared to the current one.

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  • 1685. Osorio, Andrea Diaz
    et al.
    Govindarajan, Venkatesh
    Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
    Integrated Management Spells Success for Medellin, Colombia's, Water and Wastewater Utility2013In: Journal - American Water Works Association, ISSN 0003-150X, E-ISSN 1551-8833, Vol. 105, no 3, p. 78-82Article in journal (Refereed)
    Abstract [en]

    The city of Medellin is the second largest urban area in Colombia. The state-owned company, Empresas Publicas de Medellin E.S.P. (EPM), provides water supply and wastewater treatment services to more than 3.5 million people in the city and nine other smaller towns in the conurbation. EPM also provides public services other than water supply and wastewater treatment. Eduardo Cadavid Restrepo, director of the department of water management at EPM, described the current status, challenges, and future plans for the water supply and sanitation system in Medellin in this interview (conducted by e-mail in Spanish and later translated to English) with Andrea Diaz Osorio and Govindarajan Venkatesh.

  • 1686.
    Ottoson et. al., Jakob
    KTH, Superseded Departments (pre-2005), Land and Water Resources Engineering.
    Tracking the origin of faecal pollution in surface water. An ongoing project within the European Union research programme2004In: Journal of Water and Health, ISSN 1477-8920, E-ISSN 1996-7829, Vol. 2, no 4, p. 249-260Article in journal (Refereed)
    Abstract [en]

    The objectives of this study are to generate knowledge about methods to track the sources of faecal pollution in surface waters, with the aim of having one or a few easy procedures applicable to different geographic areas in Europe. For this, a first field study using already proposed methods (genotypes of F-specific RNA bacteriophages, bacteriophages infecting Bacteroides fragilis, phenotypes of faecal coliforms and enterococci, and sterols) has been done in five areas representing a wide array of conditions in Europe. The present faecal indicators (faecal coliforms, enterococci, sulfite reducing clostridia and somatic coliphages) have also been included in this first field study. At the same time some emerging methods have been settled or adapted to water samples and assayed in a limited number of samples. The results of this first field study indicate that no single parameter alone is able to discriminate the sources, human or non-human, of faecal pollution, but that a 'basket' of 4 or 5 parameters, which includes one of the present faecal indicators, will do so. In addition, numerical analysis of the data shows that this 'basket' will allow the successful building of predictive models. Both the statistical analyses and the studied predictive models indicate that genotype II of F-specific RNA bacteriophages, the coprostanol and the ratio coprostanol: coprostanol+epicoprostanol are, out of the studied parameters, those with a greater discriminating power. Either because unsuccessful adaptation of the methods to water samples or because the preliminary assays in water samples indicated low discriminating capability, only three (sorbitol-fermenting bifidobacteria, some species of bifidobacteria detected by PCR with specific primers and phages infecting Bacteroides tethaiotaomicron) of the newly assayed methods have been considered for a second field study, which is currently underway. Expectations are that these new tools will minimize the number of parameters in the 'basket', or at least minimize the difficulty in assaying them

  • 1687.
    Ottoson, Jakob
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Comparative analysis of pathogen occurrence in wastewater: management strategies for barrier function and microbial control2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This project was initiated to fill knowledge gaps on the occurrence of pathogens in different streams of wastewater, e.g. greywater and domestic wastewater. The aims were also to measure the removal of pathogens in different treatment processes, conventional and innovative, and correlate the removal to that of common microbial process indicators, such as faecal coliforms, enterococci, Cl. perfringens spores and bacteriophages. One study also assessed the correlation between the removal of microorganisms and some commonly measured physico-chemical process indicators. The results can be applied in microbial risk assessments (MRAs) of urban wastewater systems.

    Indicators and parasitic (oo)cysts were enumerated with standard methods and viruses with rtPCR. High levels of Giardia cysts and enteroviruses were found in untreated wastewater (103.2 and 104.2 L-1 respectively) indicating high incidences in the society. Noroviruses were also often found in high numbers (103.3 L-1) during winter, but less frequent and in lower numbers (102.3 L-1) during the rest of the year. This temporal variation correlated to the clinical laboratory reporting of noroviruses. A temporal variation was also shown for Giardia with significantly lower cyst counts in untreated wastewater during spring. Cryptosporidium oocysts were not as numerous in untreated wastewater (5 L-1) reflecting a lower incidence in the society than for the other pathogens during the time of the study. Since temporal variation had a larger impact than spatial, site-specific measurements may not be necessary to perform screening level MRAs of wastewater discharge and reuse. Good data can be found in the literature and corrected for by recovery of the detection method, flow and incidence in the society. Removal of microorganisms in wastewater treatments varied from 0 to >5.8 log due to process combination and organism in question. Treatment in integrated hydroponics removed microorganism more efficiently than did secondary conventional treatment, though having longer hydraulic retention time. Tertiary treatment and treatment in a membrane bioreactor (MBR) showed better removal potential than treatment in upflow anaerobic sludge blankets (UASB) in a pilot plant. Human virus genomes were less removed and Giardia cysts more removed than all of the studied indicators. Enumeration with PCR, however, may underestimate infectious virion removal. Spores of sulphite-reducing anaerobes and somatic coliphages were significantly less removed than E. coli and enterococci in all the studied processes. Bacterial indicator and spore removals correlated to enterovirus genome removal (p<0.05), but the predictive values were low (R<0.4). Removals between microbial indicators and NH4-N, Kjeldal-N, COD and TOC correlated stronger (10-18<p<0.02; 0.43<R<0.90).

    To manage the risk with reuse and discharge of wastewater, treatment performance targets have been calculated as a step in a hazard analysis and critical control point (HACCP) approach. These targets varied from 0 to 10.4 log removal due to water (grey or wastewater), organism (rotavirus, Campylobacter or parasitic (oo)cysts) and exposure (drinking water, surface water, aerosols, irrigation of crops or public parks). Faecal contamination in greywater was measured by coprostanol and was shown to be 980 times lower than in wastewater, corresponding to 2.9 log removal in treatment. Somatic coliphages were suggested to function as an index of virus removal in wastewater treatment processes as well as to be included in the monitoring of bathing water. The guideline level was suggested to be 300 PFU 100 mL-1 based on MRA of enteroviruses. This level in a water sample would equal a probability of infection of 0.3% (95th percentile 4%). The risk is overestimated if animal sources dominate the faecal pollution. Development in methods to track sources of faecal pollution showed that if somatic coliphages are enumerated together with phages infecting Bacteroides strain GA17, discriminating human from animal faecal pollution is possible based on the ratio between the phages

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  • 1688.
    Ottoson, Jakob
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Hansen, A.
    Björlenius, Berndt
    Stockholm Water Company.
    Norder, H.
    Stenström, T.A.
    Removal of viruses, parasitic protozoa microbial indicators and correlation with process indicators in conventional and membrane processes in a wastewater pilot plant2006In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 40, no 7, p. 1449-1457Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to investigate variations in the occurrence and removal of enterovirus and norovirus genomes, Giardia cysts, Cryptosporidium oocysts and the most commonly used faecal indicators in a Swedish wastewater pilot plant. Paired samples were taken from the inlet and outlet of each treatment line: tertiary filtration, membrane bioreactor (MBR) and upflow anaerobic sludge blankets (UASB). (Oo)cysts and indicators were enumerated using standard methods and viruses using RT-PCR. Giardia cysts and enteroviruses were constantly detected, mean numbers 10(3.11) cysts and 10(4.0) PCR units L-1, respectively. Oocysts were found in 5/19 samples, mean number 5 L-1. Noroviruses were found in 6/7 influent samples, with an average titre of 10(3 28) L-1, during winter, but only in 2/15 in the rest of the year (mean 200 L-1). MBR treatment removed indicators more efficiently than did the other two lines, with 5 log removal of E. coli. Human virus genome removal did not differ between the MBR and tertiary treatment line. Microorganism removal in UASB was significantly lower for all the organisms studied. E. coli, enterococci and Cl. perfringens removal was correlated (p < 0.05) with enterovirus genome removal, with R-values around 0.4. However, values for removal of indicators were more strongly correlated to each other. Removal of viruses based on enumeration using RT-PCR probably underestimates infectious virion removal.

  • 1689.
    Ottoson, Jakob
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Norström, Anna
    KTH, School of Biotechnology (BIO).
    Dalhammar, Gunnel
    KTH, School of Biotechnology (BIO).
    Removal of micro-organisms in a small-scale hydroponics wastewater treatment system2005In: Letters in Applied Microbiology, ISSN 0266-8254, E-ISSN 1472-765X, Vol. 40, no 6, p. 443-447Article in journal (Refereed)
    Abstract [en]

    Aims: To measure the microbial removal capacity of a small-scale hydroponics wastewater treatment plant. Methods and Results: Paired samples were taken from untreated, partly-treated and treated wastewater and analysed for faecal microbial indicators, i.e. coliforms, Escherichia, coli, enterococci, Clostridium perfringens spores and somatic coliphages, by culture based methods. Escherichia coli was never detected in effluent water after >5.8-log removal. Enterococci, coliforms, spores and coliphages were removed by 4.5, 4.1, 2.3 and 2.5 log respectively. Most of the removal (60-87%) took place in the latter part of the system because of settling, normal inactivation (retention time 12.7 d) and sand filtration. Time-dependent log-linear removal was shown for spores (k = -0.17 log d-1, r2 = 0.99). Conclusions: Hydroponics wastewater treatment removed micro-organisms satisfactorily. Significance and Impact of the Study: Investigations on the microbial removal capacity of hydroponics have only been performed for bacterial indicators. In this study it has been shown that virus and (oo)cyst process indicators were removed and that hydroponics can be an alternative to conventional wastewater treatment.

  • 1690.
    Ottoson, Jakob
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Stenström, Thor Anders
    Ashbolt, N.J.
    Proposed guidelines for bathing water based on the occurrence of somatic coliphagesIn: Letters in Applied Microbiology, ISSN 0266-8254, E-ISSN 1472-765XArticle in journal (Other academic)
  • 1691.
    Ottoson, Jakob
    et al.
    KTH, Superseded Departments (pre-2005), Land and Water Resources Engineering.
    Stenström, Thor Axel
    Faecal contamination of greywater and associated microbial risks2003In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 37, no 3, p. 645-655Article in journal (Refereed)
    Abstract [en]

    The faecal contamination of greywater in a local treatment system at Vibyasen, north of Stockholm, Sweden was quantified using faecal indicator bacteria and chemical biomarkers. Bacterial indicator densities overestimated the faecal load by 100-1000-fold when compared to chemical biomarkers. Based on measured levels of coprostanol, the faecal load was estimated to be 0.04 g person(-1) day(-1). Prevalence of pathogens in the population and the faccal load were used to form the basis of a screening-level quantitative microbial risk assessment (QMRA) that was undertaken for rotavirus, Salmonella typhimurium, Campylobacter jejuni, Giardia lamblia and Cryptosporidium parvum. The different exposure scenarios simulated-direct contact, irrigation of sport fields and groundwater recharge-gave unacceptably high rotavirus risks (0.04<P-inf<0.60) despite a low faecal load. The poor reduction of somatic coliphages, which were used as a virus model, in the treatment was one main reason and additional treatment of the greywater is suggested. Somatic coliphages can under extreme circumstances replicate in the wastewater treatment system and thereby underestimate the virus reduction. An alternative QMRA method based on faecal enterococci densities estimated similar risks as for rotavirus. Growth conditions for Salmonella in greywater sediments were also investigated and risk modelling based on replication in the system increased the probability of infection from Salmonella 1000-fold, but it was still lower than the risk of a rotavirus infection.

  • 1692.
    Ottosson, Jakob
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Hansen, A.
    Westrell, T.
    Johansen, K.
    Norder, H.
    Stenström, Thor Anders
    Removal of noro- and enteroviruses, Giardia cysts, Cryptosporidium oocysts and faecalindicators at four secondary wastewater treatment plants in SwedenIn: Water environment research, ISSN 1061-4303, E-ISSN 1554-7531Article in journal (Refereed)
  • 1693. Ouyang, Wei
    et al.
    Cai, Guanqing
    Tysklind, Mats
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Yang, Wanyin
    Hao, Fanghua
    Liu, Hongbin
    Temporal-spatial patterns of three types of pesticide loadings in a middle-high latitude agricultural watershed2017In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 122, p. 377-386Article in journal (Refereed)
    Abstract [en]

    Pesticide loadings to watersheds increase during agricultural development and may vary in accordance with different crop types and seasons. High pesticide loadings can potentially result in polluted stream water. The objective of this study was to determine the pesticide loadings and concentrations of three typical pesticides (atrazine, oxadiazon, and isoprothiolane) in river water from a middle high latitude agricultural watershed in northern China. During this study, we evaluated the watershed pesticide loss patterns for two crop types over three decades. For this purpose, we integrated data from field investigations, laboratory experiments, and modeling simulations involving a distributed hydrological solute transport model (Soil and Water Assessment Tool, SWAT). SWAT was employed to compare the temporal spatial fate and behaviors of atrazine, oxadiazon, and isoprothiolane from 1990 to 2014 in a watershed area amounting to 141.5 km(2). The results showed that the three pesticides could be detected at different locations throughout the watershed, and isoprothiolane was detected at the maximum value of 1.082 mu g/L in surface runoff of paddy land. The temporal trend for the yearly loading of atrazine decreased slightly over time, but the trends for oxadiazon and isoprothiolane increased markedly over an 18-year analysis period. In regard to the pesticide concentrations in water, atrazine was associated with the largest value of nearly 1.4 mu g/L. July and August were the found to be prime periods for pesticide loss from paddy land, and the biggest monthly loss of atrazine from dryland appeared in June. Under similar usage conditions, isoprothiolane loading from paddy fields ranked as the largest one among the three types of pesticides and reached up to 17 g/ha. Limited monitoring data were useful for validating the model, which yielded valuable temporal-spatial data on the fate of pesticides in this watershed. With the expansion of paddy rice cultivation, risks for pesticide contamination of water bodies will increase. The results of this study should be valuable for future exposure and risk assessments aimed at protecting the environment and human health.

  • 1694. Ouyang, Wei
    et al.
    Huang, Weijia
    Hao, Xin
    Tysklind, Mats
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Haglund, Peter
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Hao, Fanghua
    Watershed soil Cd loss after long-term agricultural practice and biochar amendment under four rainfall levels2017In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 122, p. 692-700Article in journal (Refereed)
    Abstract [en]

    Some heavy metals in farmland soil can be transported into the waterbody, affecting the water quality and sediment at the watershed outlet, which can be used to determine the historical loss pattern. Cd is a typical heavy metal leached from farmland that is related to phosphate fertilizers and carries serious environmental risk. The spatial-vertical pattern of Cd in soil and the vertical trend of Cd in the river sediment core were analyzed, which showed the migration and accumulation of Cd in the watershed. To prevent watershed Cd loss, biochar was employed, and leaching experiments were conducted to investigate the Cd loss from soil depending on the initial concentration. Four rainfall intensities, 1.25 mm/h, 2.50 mm/h, 5.00 mm/h, and 10.00 mm/h, were used to simulate typical rainfall scenarios for the study area. Biochar was prepared from corn straw after pretreatment with ammonium dihydrogen phosphate (ADP) and pyrolysis at 400 °C under anoxic conditions. To identify the effects of biochar amendment on Cd migration, the biochar was mixed with soil for 90 days at concentrations of 0%, 0.5%, 1.0%, 3.0%, and 5.0% soil by weight. The results showed that the Cd leaching load increased as the initial load and rainfall intensity increased and that eluviation caused surface Cd to diffuse to the deep soils. The biochar application caused more of the heavy metals to be immobilized in the amended soil rather than transported into the waterbody. The sorption efficiency of the biochar for Cd increased as the addition level increased to 3%, which showed better performance than the 5% addition level under some initial concentration and rainfall conditions. The research indicated that biochar is a potential material to prevent diffuse heavy metal pollution and that a lower addition makes the application more feasible.

  • 1695.
    Owusu-Agyeman, Isaac
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Water, Sewage and Waste technology.
    Systems for ammonium concentration for further removal in the partial nitritation/anammox technology.2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Anammox is one of the main processes discovered quite recently for removal of ammonium from wastewater. Anammox process is cost effective, in that low energy and carbon source is needed. Partial nitritation is a perquisite for anammox in wastewater treatment for removal nitrogen and therefore partial nitritation/Anammox technology is studied substantially and applied in full-scale. However, the technology at present can only be used to treat high rich ammonium streams. Application of Anammox for treatment of low ammonium wastewater is not possible because of low yield of Anammox bacteria. The study aimed at devising strategies for using the Anammox technology to treat wastewater streams with low concentration of ammonium nitrogen. The objective was to get systems that could concentrate ammonium from low ammonium waste streams, so as to be able to treat it with partial nitritation/Anammox process. Two methods were used to concentrate ammonium: ion exchange and reverse osmosis. Ion exchange method was used to concentrate UASB effluents of about 24 - 40 mg NH4-N/l to 188 - 367 mg  NH4-N/l respectively which is about 9 times the initial concentrations. At VRF 5, 163 mg  NH4-N/l concentrate was attained from 41.8 mg  NH4-N/l RO feed. Results also showed that concentrates from both methods are able to be treated with partial nitritation/Anammox technology. However it took more than 32 hours to complete treatment of ion exchange concentrates while it took less than 24 hours to finish the partial nitritation/Anammox process of RO concentrates. The longer time taken can be attributed to high salinity of the concentrates which is as a result of NaCl which was used for regeneration in ion exchange process. Both ion exchange and reverse osmosis are viable methods for concentrating ammonium from UASB effluents. Dissolved oxygen was very important factor that influenced the biological process.

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  • 1696. Pahud, D.
    et al.
    Hellström, Göran
    The new duct ground heat model for TRNSYS1996In: Physical models for thermal energy stores: proceedings of the Eurotherm Seminar no 49, Eindhoven, the Netherlands / organzized by Eindhoven University of Technology, J. M. Burgers Centre for Fluid Mechanics, the Netherlands / [ed] A. A. van Steenhoven, Technische Universiteit Eindhoven, 1996Conference paper (Refereed)
  • 1697.
    Palm, Per-Martin
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering.
    Hydrological investigation for climate change adaptations in the Kou Basin Burkina Faso. : A Minor Field Study.2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    One of the biggest upcoming challenges to the international community is the problem of a changing climate. The earth’s surface temperature is rising and associated impacts on physical and biological systems are increasingly being observed. Science tells us that climate change will bring about gradual changes, such as sea level rise, and shifts of climate zones due to increased temperatures and changes in precipitation patterns.

    A changing climate affects the entire world but will strike hardest against the poorest as they are the ones most dependent on agriculture which is a sector that is very vulnerable to changes in temperature and precipitation patterns. One region that will be especially vulnerable and has experienced the problems of shifting climate zones before is the Sahel region that borders to the south end of the Sahara desert where problems of desertification have occurred before. This region will in large extent be affected if the Intergovernmental Panel on Climate Change’s (IPCC) predictions of a rising temperature will become a reality. This is one of the reasons why I have chosen Burkina Faso, situated in the south end of the Sahel region, as the objective for my MFS. The question of rising temperatures will be especially important here as the region is very sensitive to differences in temperature. A crucial topic in this part of the world as well as the topic of this study is the process of adapting to the new climatic situation.

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  • 1698.
    Palmquist, Helena
    Luleå University of Technology.
    Hazardous substances in wastewater management2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The extensive use of materials and substances in society causes diffuse source emissions that lead to uncontrolled spreading of hazardous substances, largely channelled via wastewater systems, to the surrounding nature. Complex mixtures of substances appear in wastewater as a result of use, wear, and corrosion of goods (e.g. pipes, carpets, furniture) as well as the use of household chemicals from doing the laundry and dishwashing and the use of pharmaceuticals and personal care products. As a part in analysing the flows of hazardous substances in wastewater systems, domestic wastewater fractions (greywater, urine, and faeces) were chemically characterised through full-scale field samplings at the source separating domestic wastewater systems Vibyåsen and Gebers with respect to a selected number of hazardous substances. The mass flows of hazardous metals from households emerged in similar quantities in the greywater and toilet fractions. However, ratios of hazardous metals to phosphorus and nitrogen were significantly lower in the urine than in the faecal matter and greywater. The mass flows of organic hazardous substances from households were mainly searched for in the greywater, resulting in 50-60% of the 81 measured substances being found, with representatives from all of the substance groups investigated. Of the 72 measured organic hazardous substances, 36% were found in the blackwater at Vibyåsen. However, it was not possible to exactly identify their specific sources as the mass flows of organic hazardous substances derive from numerous and diffuse household sources. The input of organic hazardous substances to urine and faeces occurs mainly via the excretion of, for instance, pharmaceuticals, pesticides, and food additives. Other examples of relevant pathways are when emptying a scouring pail and throwing in cigarette butts, snuff, etc., into the blackwater via the water closet. A possible management approach was suggested to interpret and compare different wastewater systems, and to serve to find out if and how much the flow of hazardous substances can be stopped, diverged, or transformed at the source or during transport throughout the wastewater system. The barriers approach was proposed as a tool on a conceptual level as an attempt to link the use of resources and the spreading of hazardous substances to their underlying causes and driving forces (i.e. consumption and lifestyle) rather than only focusing on the emissions. Organisational and behavioural barriers, system design, process barriers, and optional recipients were suggested, implying that various kinds of measures are needed in the management of hazardous substances to achieve a change in direction towards sustainability. It was concluded that the flows of hazardous substances in wastewater systems are not only a complex issue for wastewater management, but for society as a whole.

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  • 1699.
    Palmquist, Helena
    Luleå University of Technology.
    Hazardous substances in wastewater systems: a delicate issue for wastewater management2001Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Many substances derived from human activity end up in wastewater systems at some point. A large number of different substances - up to 30,000 - are present in wastewater. Some of them are valuable, such as nitrogen and phosphorus, but there are also hazardous substances such as heavy metals and anthropogenic organic substances. To be able to utilise the wastewater nutrients on arable land (agriculture, forestry or other alternatives), it is of great importance to investigate the sources of hazardous substances in wastewater and the human activities and attitudes that brings these different substances into the wastewater systems. For management of wastewater residues it is therefore important to be able to assess both the benefits and the risks from such products. Residues from wastewater are complex mixtures of substances, which demand a multi-sided approach for solving the problem as a whole.

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  • 1700.
    Palmquist, Helena
    Luleå University of Technology.
    Substance flow analysis of hazardous substances in a Swedish municipal wastewater system2004In: Vatten, ISSN 0042-2886, Vol. 60, no 4, p. 251-260Article in journal (Refereed)
    Abstract [en]

    In a comparative substance flow analysis two wastewater management scenarios in the Swedish town of Surahammar were assessed - a Conventional Scenario vs. a Separating Scenario. The study was restricted to a selection of 16 representative hazardous substances, including metals and organic compounds. Quantitative data of the selected hazardous substances - their presence in grey- and blackwater, and their reduction rates in the wastewater treatment plant - were gathered from the literature and our own studies. The Conventional Scenario caused an overall higher flow of the selected hazardous substances to the surrounding nature. However, the difference between both scenarios regarding emissions of hazardous substances to the receiving water was small. In general, the Separating Scenario resulted in a significantly smaller flow of hazardous substances to arable land than the Conventional Scenario. A possible management approach was suggested to be used to interpret and compare different wastewater systems, and serve to find out if and how much the flow of hazardous substances can be stopped, diverged, or transformed at the source or during transport throughout the system. System design, process barriers, and organisational and behavioural barriers were suggested, but only the first two were assessed in this study.

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