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Enhanced ozone mass transfer and organic (micro)pollutant removal in packed bubble columns
No full textOzone-based processes are effectively used for e.g. removing organic (micro)pollutants from municipal secondary effluent and oxidizing contaminants from industrial wastewater. Nevertheless, the practical application of the ozonation technique is still facing some challenges. The first one is the formation of oxidation intermediates owing to the low mineralization efficiency during ozonation. Second, the low ozone gas/liquid mass transfer limits the overall oxidation reaction efficiency. As ozone gas generation is an energy-intensive process, this also reduces the cost-effectiveness. As such, enhancing the ozone mass transfer and achieving high ozonation efficiency at low energy consumption is essential for expanding the practical application of ozonation. The third challenge is related to the elimination of micropollutants by ozonation. It is difficult to monitor the removal efficiency of micropollutants in real-time because frequent (chromatography based) analysis of each compound with low concentrations is costly and time-consuming. As such, developing reliable and efficient online-monitoring methods for micropollutants removal during ozonation is needed. Based on these challenges, the first chapter gives a critical literature review on the ozonation process and ozone mass transfer enhancement techniques. According to this review, applying granular mineral solids as active packing materials in a packed ozone reactor, which has not yet been studied, is proposed to be a promising method to improve the ozone mass transfer and oxidation efficiency. Additionally, the research progress in surrogate-based monitoring and control strategies of micropollutants ozonation is reviewed in Chapter 1. The removal of dissolved organic matters (DOM, mainly represent by UV254) can be used as a reliable and robust surrogate to monitoring the removal of micropollutants in a conventional bubble column. However, its feasibility in the application of packed columns has not yet been investigated. Based on these research gaps, this thesis is mainly working on using mineral-packed bubble columns to enhance the ozone mass transfer, achieve high target organic (micro)pollutants removal, and reduce oxidation intermediates generation with low energy consumption. The feasibility of combining ozonation in packed bubble columns with other treatments was also studied. The specific research aims are listed in Chapter 2. The outline of this thesis is also shown in Chapter 2. The details of the experiment setups, materials, and methods are given in Chapter 3.
In this thesis, lava rock, metal pall rings and expanded clay aggregates (ECA) were used as packing materials to build packed bubble column (LBC, MBC, and EBC, respectively) and compared with non-packed bubble column (BC). In Chapter 4, the ozone gas/liquid mass transfer efficiency in BC, MBC and LBC was determined in a countercurrent continuous mode by calculating the height of packing equivalent to one transfer unit (HOG), where a lower HOG represents a higher mass transfer efficiency. Compared with the HOG value of BC (17 m), that of LBC (6 m) and MBC (11 m) was 65% and 35% lower. Furthermore, in Chapter 5 and 6, ozone mass transfer tests were conducted in semi-batch mode to determine their volumetric mass transfer coefficient values k_L a of ozone at pH=7 and T=20 °C. The LBC had the highest value 0.62 min-1, followed by EBC (0.58 min-1), MBC (0.42 min-1) and BC (0.24 min-1), showing the packed bubble columns increased the ozone gas-liquid mass transfer efficiency and lava rock had the best promoting performance.
Meanwhile, the effect of these packing materials on the organic pollutants (focusing on DOM and specific micropollutants) degradation by ozonation was studied. In Chapter 4 humic acids (HA) were used as model pollutant to evaluate the ozonation performance of different columns since HA is widely present in natural water and various types of wastewater and has adverse effects on water quality. The use of LBC and MBC increased the HA removal efficiency by 19%~26% at 33.3 mg/(Lcolumn h) (i.e. 0.8 g O3/g COD) of ozone dose, compared to BC. The O3 utilization efficiency was improved by up to 42% and the energy consumption (EEO) for HA removal was decreased by 5%~51%.
In Chapter 5 and 6, LBC, MBC and BC were used to ozonate real wastewater (bio-treated landfill leachate) which contains bio-refractory organic compounds including DOM and micropollutants. In Chapter 5 mainly the DOM removal from bio-treated landfill leachate was investigated. Insight into the formation of oxidation intermediates from DOM in the leachate during ozonation was provided. At an O3 dose of 0.6 g O3/g COD, the COD removal efficiency was 32% in MBC and 46% in LBC, which was 6% and 20% higher than that in BC (26%). The presence of lava rock decreased the energy consumption for COD removal by about 53%, i.e. from 38 kWh/m3 in BC to 18 kWh/m3 in LBC. The lowest operating cost for per kilogram COD removal (2.53 €/kg COD) was achieved in LBC. Gas chromatography–mass spectrometry (GC-MS) analysis showed that MBC and LBC improved the further oxidation efficiency of DOM from the bio-treated landfill leachate and reduced intermediate products during ozonation.
In Chapter 6 the abatement of micropollutants from biotreated landfill leachates was investigated, as well as the correlation between micropollutant removal and the reduction of DOM represent by UV254 absorbance (ΔUV254). Results showed both mineral materials (lava rock and ECA) had a comparable beneficial effect towards micropollutants ozonation and their intermediates degradation. The removal efficiency of O3-recalcitrant compounds (diuron, atrazine (ATZ) and alachlor (ALA)) increased by 20%-40% and the ΔUV254 increased by over 20% in LBC and EBC in comparison with that in BC. In view of process control, a two-stage linear correlation between the O3-recalcitrant compounds (ATZ and ALA) removal and ΔUV254 was observed.
In addition to a single stage ozonation process, the packed bubble column was used as a pre- or post- treatment unit in a treatment train in Chapter 7 and 8. In Chapter 7, the ozonation process was followed by an adsorption process to recover Ortho-phosphate (Ortho-P) from a phosphonate, i.e. 1-hydroxyethane-1,1-diphosphonic acid (HEDP) containing waste water. Mineral packed bubble columns including LBC (86%) and EBC (72%) showed higher net Ortho-P production efficiency than BC (59%). Afterwards, the produced Ortho-P in the ozonated effluents was adsorbed and recovered by a waste product, i.e. iron coated sand (ICS) granules. The highest Ortho-P recovery efficiency (66 %) was achieved by ICS adsorption after ozonation in the LBC column, followed by EBC (62 %) and BC (38 %).
Furthermore, in Chapter 8, the ozonation process following a biological treatment process was studied. Considering that microorganisms might have some tolerance to ozone, chapter 8 investigated the feasibility to combine the biological treatment process with the in-situ ozonation process in the same bioreactor unit. An ECA-packed biofilm column (EBC) was run and operated for 150 days. In the first experimental period, a biodegradation process was operating at a residence time of 48 h. About 85% of the total inorganic nitrogen can be removed from the raw landfill leachate biologically. About 90% of the biodegradable micropollutants (bisphenol A, 17α-ethinylestradiol and alachlor) could be removed as well, while a large percentage of recalcitrant compounds such as carbamazepine (CBZ, around 70%) and atrazine (ATZ, about 30%) remained in the effluent. In a second experimental period, ozone gas was gradually introduced into the biofilm reactor in situ to further remove the bio-refractory micropollutants. At an ozone dose of 0.4 g O3/g COD, the residual target micropollutants (ATZ, CBZ) were completely removed. Meanwhile, the high nitrogen removal efficiency can be maintained at 85%, which was attributed to the high abundance of nitrifying and denitrifying bacteria in the reactor indicated by the results of the 16S rRNA analysis.
Overall, this PhD research provides comprehensive insights into the enhanced ozone mass transfer and removal of the organic (micro)pollutants by ozonation in minerals packed bubble columns. The findings and results were discussed in Chapter 9. Some perspectives on potential future research are provided as well
Methodologies for analog-to-digital conversion with high bandwidth and high accuracy based on voltage-controlled oscillators
No full textDoor de technologie schaling van CMOS componenten in de laatste paar decennia, is de efficiëntie en snelheid van digitale elektronica zodanig gestegen, dat een steeds groter wordende functionaliteit naar het digitale domein wordt geduwd. Door de toenemende bandbreedte en vraag naar hogere datasnelheid, samen met het feit dat meer functionaliteit naar het digitale domein wordt geduwd, worden de prestatie eisen van deze omzetting van het analoog- naar het digitaal domein steeds strikter. In dit proefschrift worden tijdscodering gebaseerde omzettingstechnieken gebruikt om deze strikte prestatie eisen te behalen, en om maximaal voordeel te halen uit de nieuwste CMOS technologieën. Eerst werd er een breed theoretisch kader opgesteld, wat het mogelijk maakt om deze componenten op een zo efficiënt en compact mogelijke manier te vervaardigen. Op basis van dit nieuw theoretisch kader werd dan tenslotte een prototype chip gefabriceerd in een 28nm CMOS technologie. Het prototype vertoonde een resolutie van meer dan 10 bit met een bandbreedte van 125 MHz en behaalde deze specificaties met een competitief verbruik van 54mW. Met een chip oppervlakte van slechts 0.014mm², is het in vergelijking met de beste hedendaagse gepubliceerde designs met vergelijkbare specificaties, zeer overtuigend de meest compacte oplossing
Constructing leniency policies : economic effects and implications of granting leniency in cartel cases
No full textThe dissertation delves into leniency policies in antitrust enforcement, which incentivize cartel members to reveal wrongdoing in exchange for reduced penalties. While these policies are effective in detection and deterrence, relying solely on them can yield suboptimal outcomes. The dissertation underscores optimizing policy design based on factors such as collusion, transaction, and information costs. Notably, it highlights the need for both independent investigations by the antitrust authority and self-reporting and addressing practical challenges such as parallel proceedings and access to leniency documents. In this context, international cooperation is found to be crucial for combating international cartels. From a welfare perspective, the dissertation underscores limiting transaction costs and welfare losses from hiding by cartel members and finds that confidential disclosure policies can be welfare-maximizing
Mobile immersive virtual reality in secondary education : from affordances to implementation
No full textMen's engagement in maternal, newborn and child care : promoting health and gender equality
No full textExecutive summary (English)
Women, newborns and children in low- and middle-income countries face an unfair and unacceptably high burden of poor health in pregnancy, during and after childbirth, and in the first five years of life.
The burden of poor maternal, newborn and child health (MNCH) in low- and middle-income countries is largely preventable through high coverage of essential health services, combined with optimal caregiving and other health promoting behaviours. Gender inequality is a key driver of poor MNCH in low- and middle-income countries, and working with men as well as women has been recognised as a promising strategy to improve gendered MNCH outcomes. Some interventions to influence men’s engagement in MNCH have been demonstrated to increase uptake of essential MNCH services and improve the quality of caregiving and health promoting behaviours. Overall, however, the evidence base for this approach is patchy, and inconclusive.
The aim of this thesis is to investigate how interventions designed to influence men’s engagement in MNCH can be made optimally effective for the health and wellbeing of women and children, particularly in low- and middle-income countries. This is addressed by, first, assessing the effectiveness of these interventions on MNCH outcomes, and then identifying key mechanisms through which the interventions achieve any observed positive effects. An exploratory sequential mixed-methods design is used to integrate findings from two evidence syntheses and two primary studies in an iterative, reflective process of hypothesis development. Findings across the four studies are integrated to propose a detailed hypothesis – a theory of change – for interventions designed to
influence men’s engagement in MNCH.
The first two papers submitted for this thesis report on a systematic review of the effectiveness of male involvement interventions for maternal and newborn health outcomes in low- and middleincome countries. The review identifies that these interventions can improve health service utilisation and home care practices, while at the same time finding variable intervention effects with some harmful outcomes (Chapter 4.1). Secondary content analysis of studies included in the systematic review (Chapter 4.2) applies a critical gender lens to explore how interventions engaging with men can support gender-transformative change and identify factors that may underpin the variable and harmful outcomes identified through the effectiveness review; this analysis identified lines of enquiry that were explored through subsequent primary studies and a global evidence synthesis.
The third paper submitted for this thesis reports on a primary qualitative study exploring the experiences of men and women in Tanzania and Zimbabwe who had been exposed to interventions designed to influence men’s engagement in MNCH (Chapter 4.3). Study findings highlight the importance of increased love, happiness and emotional intimacy in coparent relationships, both as a wellbeing outcome valued by women and men, and as a contributor to the effectiveness of
interventions engaging with men for MNCH.
The fourth paper submitted for this thesis reports on a cluster-randomised controlled trial of a gendersynchronised intervention with women and men in rural Zimbabwe, which was designed to support men’s positive engagement in MNCH (Chapter 4.4). Trial results demonstrate that the intervention enhanced men’s practical support for women and infants, enabled coparents’ equitable, informed MNCH decision-making, and improved maternal mental health and MNCH care-seeking.
The final paper submitted for this thesis presents the results of a global qualitative evidence synthesis of the experiences of women, men and health providers relating to interventions designed to influence men’s engagement in MNCH (Chapter 4.5). Findings indicate that interventions enable
health service utilisation and improve the quality of care for women, newborns and men, and also strengthen family relationships. Synthesis findings also illustrate that poorly designed or implemented interventions can constrain some women’s access to health services and compound the negative
impacts of existing gender inequalities. Finally, findings highlight the importance of context, including health system factors, gender norms, sociodemographic characteristics, and household needs, on intervention uptake and outcomes.
Overall, thesis findings provide persuasive evidence that interventions to influence men’s engagement in MNCH can have substantial benefits for women’s, newborn’s and children’s health. Findings indicate key mechanisms through which interventions can improve MNCH: more loving and genderequal
coparent relationships, men’s increased practical support for MNCH, and men’s improved health and wellbeing. Findings also highlight the influence of health system context and established and emerging gender norms, and the importance of considering these factors in intervention design and delivery. The proposed theory of change illustrates how interventions seeking to influence men’s engagement in MNCH can target these mechanisms in order to improve both health and gender equality.
The main recommendation emerging from the thesis is presented in the form of the theory of change. This theory of change indicates key mechanisms, predominantly at the individual and interpersonal level, through which interventions to influence men’s engagement in MNCH can lead to improved
health and gender equality outcomes. It is hoped that policymakers and programmers will use, contextualise, and adapt the theory of change developed through this thesis, in order to support the design, delivery and monitoring of interventions that engage effectively with men to achieve optimal
benefits. Thesis findings also highlight the critical importance of a gender-transformative approach to engaging with men for MNCH. Consequently, a strong recommendation emerging from the thesis is that interventions designed to influence men’s engagement in MNCH should incorporate locally relevant gender-transformative messages and approaches, and monitor the extent to which established and emerging local norms around fatherhood, motherhood, coparenting and caregiving enable men’s positive involvement in MNCH.
Work completed for this thesis has also highlighted ways in which health systems can constrain men’s ability to engage in MNCH. Health policy and health services stakeholders should implement supply side interventions to enable men’s engagement in MNCH services and other health services, using a
health system strengthening approach to ensure that these changes do not place an unacceptable strain on existing services. There is also the opportunity for health and social services to better support critical outcomes that optimise the benefits of men’s engagement in MNCH. Specifically, services that
reach one or both parents during the perinatal period should provide screening and support for both paternal and maternal health, and should also incorporate some degree of support for positive coparent and father-child relationships where this can be done without compromising service quality or safety.
Finally, to avoid causing harm, policies and programs designed to influence men’s engagement in MNCH should respond to the reality of diverse families, women, and men, by consulting with diverse stakeholders, using inclusive messages and approaches, and ensuring that intended outcomes are
relevant and acceptable to the target population.
Future research will be needed to further strengthen and consolidate the evidence base in this rapidly evolving field, by assessing the outcomes and processes described in the proposed theory of change, including maternal and paternal mental health. Implementation research is also required to develop
practical guidance for designing interventions and maintaining implementation fidelity, particularly regarding gender-transformative messages and delivery strategies
Introducing nuance to the measurement of consumers' automatic product appraisals : validation and applications of the Implicit Attribute Classification Task (‘IMPACT’)
No full textApplication of metagenomics for antimicrobial resistance detection in a One Health context
No full textEwing sarcoma
No full textEwing sarcoma (ES) is the second most common primary musculoskeletal neoplasm in children and adolescents after osteosarcoma with a peak between 10 and 20. Rarely, the tumor develops in newborns or in adults over the age of 30. ES can affect either the appendicular or axial skeleton. Extraosseous ES is less prevalent. Clinical presentation is usually nonspecific. Radiography is the initial method for detection and imaging characterization of osseous ES. Computed tomography is used to assess bone destruction and characterization in anatomically complex areas, such as the spine and pelvis. MRI is the preferred imaging modality for local staging. The most characteristic finding on MRI is the presence of a large soft tissue mass. The definitive diagnosis of ES relies on a combination of histology, immunohistochemistry, and molecular testing. At initial presentation, 20%–30% of patients have pulmonary and/or skeletal metastases. The workup for pulmonary metastases includes a CT scan of the chest. PET-CT or WB-MRI is becoming standard for staging of osseous and nonosseous metastasis. The most important prognostic factor in ES is the presence or absence of metastasis. Follow-up imaging is performed during and after treatment, using the same imaging modalities as for initial workup
