112 research outputs found
Route optimization in dynamic flow fields: avigation system for the North Sea and Wadden Sea
No full textThis thesis introduces a new algorithm for optimising shipping routes within a dredging project. Highly dynamic and time-dependent hydrodynamic features influence shipping routes. Due to the complex interactions between the horizontal tide, vertical tide, stratifying forces, wind-driven forces, and limited water-depth, shipping routes were previously only optimised for large scale routes (order of 1000 km). This study presents an algorithm that can optimise shipping routes that are influenced by these small scales (order of 10 km) hydrodynamic features. This algorithm uses graph theory to solve for the time-dependent fastest path between start and destination. Graph theory searches for the optimal path through a set of nodes that are connected with edges. This study uses the time-dependent shortest path algorithm which accounts for the FIFO-criteria (Waiting criteria) and can solve the non-convex nature of the problemThe input of this algorithm is a hydrodynamic model. These models are Computational Fluid Dynamic (CFD) models that calculate currents and water levels in a specific domain. The domain is discretised into cells and nodes to calculate these hydrodynamic features. This study uses the nodes of this hydrodynamic model as the vertices of the graph. However, for some cases, the hydrodynamic model has too many nodes for the shortest path algorithm. This study presents a method for reducing the number of nodes without reducing the spatial resolution. The nodes are reduced based on a combination of the vorticity and the magnitude of the flow. This algorithm is implemented in a python software package named Hydrodynamic Algorithm for Logistic enhancement Module (HALEM). HALEM can determine the optimal shipping route for a given hydrodynamic model. Defining different cost functions results in different optimisation purposes. This thesis presents cost functions for the fastest route, shortest route, cheapest route and least polluting route. This software is then implemented in the OpenCLSim software so that this combination of software can optimise routes of entire projects. A case study simulates a beach-nourishment at Schouwen Westkop Noord to demonstrate the practical use of HALEM and OpenCLSim. For this project, 425,500 m3 sand should be dredged offshore and pumped onto the beach. Due to the narrow gullies and tidal changes in hydrodynamic features, the routes were hard to predict. The simulation with HALEM and OpenCLSim shows an increase in the production with 21 % compared to the simulation with just OpenCLSim.Civil Engineering | Hydraulic Engineerin
Assessment of Fe(II), Fe(III) and NaMnO4 dosing for As removal <1 µg/L during aeration-filtration at WTP Prinsenbosch
No full textIn 2013, Brabant Water (BW) adopted a new goal of <1 μg/l for As level in the drinking water, resulting in the need to enhance As removal at seven water treatment plants (WPT’s), including WTP Prinsenbosch (As = 2.6 μg/l). Earlier experiences of BW at WTP Dorst had shown that dosing of NaMnO4 to an aeration-filtration system efficiently reduces As concentrations. However, the so-called AOCF method had undesired operational side-effects, including decreased filter run time, breakthrough of particles and poor thickening of backwash sludge. The aim of this thesis was to investigate 3 process alternatives (respectively dosing of NaMnO4, Fe(III) and Fe(II)) to enhance the As removal to < 1 μg/l at WTP Prinsenbosch, specifically including the impact on operational aspects like the filtration process and the backwash water production and sludge properties. The assessment is based on the results of (full-scale and) pilot-plant research at WTP Prinsenbosch. It was found that Fe(III) was slightly more effective than Fe(II) and NaMnO4 for the removal of As, but at doses of 1.3 mg/l NaMnO4, 0.7 mg/l Fe(III) or 1.2 mg /l Fe(II) a drinking water quality of 0.7 μg As/l could be obtained with all 3 chemicals. In rapid sand filters, As(III) is oxidized biologically leading to subsequent adsorption of As(V) onto Fe(III)oxyhydroxides and Mn(IV) oxides. It was found that the adsorption capacity of the filter precipitates was relatively high, because to obtain a concentration of 0.7 μg As/l, the acceptable adsorption load was between 1.4-1.7 μg As/ mg (Fe+Mn). Although As removal was similar for dosing either 1.3 mg/l NaMnO4, 0.7 mg/l Fe(III) or 1.2 mg /l Fe(II), the impact on the filtration process and the backwash water production and sludge properties proved to be quite different. Dosing of NaMnO4 and Fe(III) led to shorter filter run times, increased vulnerability to breakthrough, higher backwash water production and reduced thickening of the sludge. Contrarily, dosing of Fe(II) and the reference case (without dosing) led to longer run times, no breakthrough, lower backwash water production and superior thickening of the sludge. The differences in the impact on the filtration process and sludge properties between Fe(II) and Fe(III) and NaMnO4 are most likely explained by a different density of the Fe(III)oxyhydroxides and Mn(IV) oxides formed in the filter. The different density may be related to the formation process (biotic or abiotic oxidation of Fe and Mn, homogeneous or heterogeneous precipitation of Fe(III)oxyhydroxides and Mn(IV) oxides) and the crystal structure and density (which may be influenced by Eh and pH). The conclusion of the research for WTP Prinsenbosch is that Fe(II) is the preferred chemical in view of the superior operational aspects. It is also cheaper than NaMnO4 (both chemical costs and sludge disposal costs) and easier to handle
Care for adult non-ICU Covid-19 patients: early experiences from a Belgian tertiary care centre
No full textThe current Covid-19 outbreak poses many challenges on hospital organisation and patient care. Our hospital lies at the epicentre of the Belgian epidemic. On April 1st, a total of 235 Covid-19 patients had been admitted to our hospital. This demanded an unprecedented adaptation of our hospital organisation, and we have met many clinical issues in the care for Covid-19 patients. In this article, we share our experience in the handling of some of the practical and organisational issues in the care for Covid-19 patients.van der Hilst, J (reprint author), Jessa Hosp, Dept Infect Dis & Immun, Hasselt, Belgium.
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Care for adult non-ICU Covid-19 patients: early experiences from a Belgian tertiary care centre
No full textThe current Covid-19 outbreak poses many challenges on hospital organisation and patient care. Our hospital lies at the epicentre of the Belgian epidemic. On April 1st, a total of 235 Covid-19 patients had been admitted to our hospital. This demanded an unprecedented adaptation of our hospital organisation, and we have met many clinical issues in the care for Covid-19 patients. In this article, we share our experience in the handling of some of the practical and organisational issues in the care for Covid-19 patients.van der Hilst, J (reprint author), Jessa Hosp, Dept Infect Dis & Immun, Hasselt, Belgium.
[email protected]
Nano zero valent iron amended ceramic pot filters for enhanced virus and arsenic removal
No full textWorldwide 748 million people lacked access to improved sources of drinking water in 2014, of this group almost a quarter relies on untreated surface water (WHO & Unicef, 2014). According to the WHO, simple, socially accepted and low-cost household water treatment systems (HWTS), such as the Ceramic Pot Filter (CPF), can provide a solution for reliable drinking water on the short term. Although CPFs are used worldwide and are generally effective with regard to bacteria removal, they can in most cases not be indicated by the WHO as a “protective” HWTS, since the virus removal is insufficient. Another limitation of the CPF is the incapability of removing arsenic. Prolonged ingestion of water with elevated arsenic levels can lead to severe health issues including dermal lesions and various types of cancers (WHO, 2011b). The objective of this study was therefore to provide reliable experimental data to investigate whether it is feasible to extend the capabilities of CPFs with arsenic removal properties and enhanced virus inactivation by the incorporation of nano Zero Valent Iron (nZVI), which is a well-known arsenic adsorbent and has also potential capabilities for virus reduction. As a basis for the research approach, the following sub-objectives were formulated: (i) study the arsenic adsorption capacities nZVI amended CPFs, (ii) determine the microbiological inactivation efficiency by nZVI amended CPFs, (iii) evaluate the leaching of the incorporated nZVI and (iv) provide knowledge on the effect of incorporating nZVI into CPFs before firing. In this study Ceramic Disk Filters (CDFs) manufactured by combining clay soil with water and sawdust, pressing them in a disk shape and, firing them. Additionally, metals (nZVI, Composite Iron Matrix powder or silver nanoparticles (nAg)) were added to the clay mixture before firing, to obtain an iron content of 0.05%, 0.5% or 5% based on the weight of a dry disk. The manufactured CDFs were tested based on the following established requirements: (i) arsenic must be removed to below the provisional WHO guideline of 10 ?g/L, (ii) for bacteria a LRV of 2 or greater is required, (ii) for viruses a LRV of 3 or greater is required, (iv) the leached amount of metals must not exceed the WHO guidelines and (v) CDFs should have a flow rate of 0.08-0.24 L/h, which corresponds to 1-3 L/h for a full-size CPF. The removal of bacteria and viruses was quantified by loading the CDFs with test water with Escherichia coli and MS2 bacteriophages, as indicator organisms for bacteria and viruses, respectively. During this filter experiment also the metal leaching from the CDFs was evaluated, an arsenic breakthrough experiment was performed and the flow rates were measured. Furthermore, batch experiments were conducted with ground CDFs, both fired and unfired, to get more insight on the capabilities of the adsorption and inactivation of MS2 bacteriophages and the removal of arsenic, and to study the consequences of firing nZVI into the CDFs. Moreover, knowledge was obtained on the effect of firing nZVI into ceramic material by means of X-ray diffraction (XRD), 57Fe Mössbauer spectroscopy, optical microscopy and Scanning Electron Microscope – Energy Dispersive X-ray (SEM-EDX). The main findings, with regard to the requirements for a CPF, were: (i) although this study showed that ZVI on itself is an effective arsenic adsorbent an immediate total arsenic breakthrough of 200 ?g/L was observed for the CDFs with 5% nZVI; (ii) all CDFs, except the filter with 0.05% nZVI, were able to remove E. coli sufficiently to meet the requirements for bacteria removal (LRV 0.75-4.28); (iii) MS2 bacteriophages were poorly removed (LRV 0.11-0.24) (iv) there is no health-based guideline of the WHO for iron and the leached silver stayed far below the maximum WHO guideline of 0.1 mg/L; (v) the translated flow rates for CPFs were for all type filters higher than the requirement of 1-3 L/h (3.4 – 15.6 L/h), except for the filter with 0.05% nAg (1.5 L/h). Overall, it can thus be concluded that it is not recommended to incorporate nZVI in CPFs before firing with the purpose to enhance the removal of arsenic and viruses. Although, ZVI on itself is well capable of removing arsenic, especially at nano-scale, it was found that when it is incorporated into clay it looses effectiveness and when the clay is fired even more. In the batch experiments the unfired crushed CDF with 5% nZVI was able to remove approximately 90% of the initial 200 ?g/L As(III) in 30 minutes of contact time, while the fired crushed CDF only removed a few per cent As(III). Part of the faster As(III) removal of the unfired filter was a result of sorption by the clay, but the nZVI contributed considerably. Although, the LRVs for MS2 bacteriophages by fired filter material were higher in the batch experiment (LRV 0.42-1.52) than in the filter experiment – probably due more intensive contact - there was also no enhanced MS2 bacteriophage reduction noticed for the fired CDFs with nZVI compared to the fired blank CDF. There are probably several reactions that caused this loss of performance of ZVI. The results of the filter experiments indicated that there was insufficient surface contact with the nZVI particles; either due to unavailability of nZVI particles on the pore surface or due to too high flow rates. The addition of nZVI particles namely led to a considerable increase of flow rate, probably as a result of successive expansion and shrinking of the nZVI during firing. Furthermore, it is hypothesized that due to the vitrification process, in which the clay bonds together, the nZVI became enclosed in the clay structure. Furthermore, the 57Fe Mössbauer spectra evidenced that during firing all the added nZVI was oxidized into hematite, which probably affects the removal of arsenic. Different ZVI corrosion products have a different ability to adsorb arsenic: ZVI exhibits the greatest arsenic adsorption, secondly magnetite, then hematite and lastly goethite (Mamindy-Pajany et al. (2011)). This study showed that ZVI has potential for the removal of arsenic in HWTS, but with application in a different setting than by firing it in the CPF. Suggestions were made for potential alternatives: (i) CPFs with an iron coating; (ii) CPF with ZVI pre-treatment in the form of an hang-element or an extra bucket on top of the CPF, like the effective SONO filter for arsenic removal (Neumann et al., 2013); (iii) CPF with inside iron mixed ceramic pellets (Shafiquzzam et al.,2013). When designing a new type of CPF it is important to make sure that the iron (oxides) particles can be reached and that the flow rate is not too high, which ensures that the contact time with the iron (oxides) particles is long enough. Furthermore, additional research is needed on the enhancement of virus removal and inactivation. It is recommended to study the combination of nZVI and nAg in more detail and also to look at other combination of metals, such as Ag and copper. In order to better understand the adsorption of viruses onto different media it is advised to perform to determine the actual pHPZC of the used media. Lastly, it is advised that in a later stage of future research experiments should be performed with more challenging water and varying parameters such as the turbidity, the pH, competing ions, the ionic strength, influent arsenic concentration and different types of viruses.Sanitary EngineeringWater ManagementCivil Engineering and Geoscience
Subsurface iron and arsenic removal for drinking water treatment in Bangladesh
No full textArsenic contamination of shallow tube well drinking water is an urgent health problem in Bangladesh. Current arsenic mitigation solutions, including (household) arsenic removal options, do not always provide a sustainable alternative for safe drinking water. A novel technology, Subsurface Arsenic Removal, relies on the existing technology of Subsurface Iron Removal. The principle of this technology is that aerated water is periodically injected into an anoxic or anaerobic aquifer through a tube well. The injection water partially displaces the original iron and arsenic containing groundwater. The oxygen-rich injection water oxidized adsorbed iron on the soil grains around the tube well. Once the flow direction is reversed, the oxidized iron (precipitated as iron (oxy)hydroxides) provides adsorption sites for soluble iron and arsenic. Subsequently groundwater with reduced iron and arsenic concentrations can be abstracted. This technology has the potential to be an affordable, robust and chemical-free arsenic removal solution for decentralized application. In this PhD study a combination field and laboratory research, in Bangladesh and the Netherlands, has resulted in better understanding of the subsurface processes determining the sustainable operation in diverse geochemical settings.Water MangamentCivil Engineering and Geoscience
Performance of photobioreactor, constructed wetland and anaerobic membrane bioreactor in treating antibiotic resistant bacteria in the Barapullah drain, New Delhi, India
No full textLimitless usage of antibiotics has led antibiotic resistance to be one of the largest threats to world health and development. In this study, the concentrations of Extended spectrum betalactamase Escherichia coli and carbapenem resistant Escherichia Coli was assessed in a major drain in New Delhi, India. The performance of Anaerobic membrane bioreactor, photobioreactor and constructed wetlands in treating ESBL-E.coli and CRE-E.coli was evaluated. The results showed ESBL-E.coli and CRE-E.coli removal efficiencies of 99.82% and 99.69% for AnMBR, 99.62% and 99.86% for PBR and 98.1-99.3% for constructed wetlands respectively. Log10 reduction values of 2.7-3 for AnMBR, 2.8-3.2 for PBR and 1.82.3 for CWs was achieved in this study. Coupling micro-aeration with AnMBR improved the removal efficiency by 36-46%. A quantitative microbial risk assessment showed probability of infection by Enterotoxigenic E.coli (ETEC O55) post treatment to be reduced below 10-18% for AnMBR and PBR and below 20-35% for CWs. Treated effluents accounted for a high reduction in the total DALYs pppy by 63% for PBR, followed by 41.6% for AnMBR and 12.5% for CWS. ESBL-E. coli and CRE-E.coli counts decreased below the monitoring level of 103-105 for unrestricted irrigation and 104-105 for restricted irrigation as declared by WHO. Treated water was not recommended for direct consumption due to higher risk above 10%. This study exhibits the potential of these efficient and sustainable technologies in treating antibiotic resistant bacteria. CIE5050-09 Additional Graduation WorkLOTUS-H
Electrocoagulation as a tertiary treatment of municipal wastewater: Removal of enteric pathogen indicators and antibiotic-resistant bacteria
No full textWith the growing population and economic development, there is more stress on natural water resources. Additionally, current and future water shortages, increasing environmental concerns and stringent discharge standards demand high-quality treated water. In this scenario, it is crucial to recover water and wastewater resources for reuse, reducing the dependency on new resources. While aiming for water reclamation, the influence of wastewater quality parameters on human health is given foremost attention in recent times. Enteric pathogens are a major concern when reclaiming municipal wastewater. Electrocoagulation (EC) process that introduces coagulants by electrochemical means has been successfully employed for the treatment of groundwater, industrial and municipal wastewater. EC has been widely accepted over other physicochemical processes due to its process design and lowcost material. In this research, EC has been thoroughly investigated as a tertiary treatment technology for water reclamation from municipal wastewater. This research is focused on determining the efficiency of low voltage iron EC for the removal of enteric pathogen indicators and antibiotic-resistant bacteria from secondary wastewater effluent. The effect of operational parameters: charge dosage (C/L) and charge dosage rate (C/L/min) on pollutant reduction was evaluated in different water matrices: demineralized water, synthetic wastewater effluent and real wastewater effluent. EC operated at 400 C/L, 7.2 C/L/min and natural pH allowed > 3.5 log units removal for E. coli and Enterococci, > 2.5 log units for ESBL E. coli and VRE and > 2 and 2.7 log units for Somatic coliphages and Clostridium perfringens spores respectively in real wastewater effluent. Furthermore, a significant reduction of phosphorous, COD and the true color was observed at 400 C/L and 36 C/L/min. Pollutant reduction was influenced by sedimentation and floatation mechanisms observed at varying charge dosage rates. A marginally higher removal rate constant of pathogen indicators as a function of charge dosage at low charge dosage rate showed slow iron dosing to improve microbial adsorption and increase contact time with iron precipitates. The reduction of pathogen indicators was associated with physical removal mechanisms like adsorption, sweep coagulation and entrapment within the flocs, charge neutralization and aggregation based on literature. The effective removal of physical, chemical and microbiological parameters in real wastewater effluent was achieved at 400 C/L and 7.2 C/L/min at an operating cost of 0.17 €/m3 indicating EC to be a cost-effective treatment in comparison to alternative technologies like ozone, UV, activated carbon and reverse osmosis
An Umbrella as a Mobile Acoustic Rain Gauge for use in Urban Areas
No full textTo validate rainfall intensity in urban areas measured by satellite a first prototype proof of concept is introduced and tested. Using low-cost electronics an umbrella is converted into a mobile acoustic rain gauge which can be used in urban areas to measure rainfall intensities. A reed switch is placed in the umbrella to measure whether the umbrella is open or closed. Using a piezoelectric sensor and a Sparkfun sound detector rain droplets are detected and using a Pycom WiPy send over Bluetooth to an application which saves it on an online server. Tests during a laboratory experiment to see how the output data evolves shows that the data collected have an output range of about 10 % compared to its mean value. During field evaluation, to compare its output data with rainfall intensities as measured with radar, it is shown that the output data follows the radar measurements within acceptable bounds
Optimising the Ripening Period of Slow Sand Filters
No full textThis work is carried out in collaboration with Dunea and TU Delft. The aim of this study was to optimize the ripening period of slow sand filters and to identify the indicators of ripening. Combination of full scale and column scale slow sandfilters were used to achieve the goals. Two full scale and eight column scaleslow sand filters were used in the study. Ripening period is required for the formation of biological community (schmutzdecke layer) over the sand layer and within the top layers of the sand bed during which filter performance is sub-optimal. The ripeningperiod depends on factors such as influent water quality (nutrient loading), temperature and filtration rate. In order to optimise the ripening period of slowsand filter, two possible approaches were investigated. First, how can we retain the maximum biological activity within the filter bed at the time of scraping (optimise scraping) and second how to accelerate the growth of microorganism when a filter is put into operation by changing operational parameters.In order to ensure maximum biological activity is retained within the filters at the time of scraping, biomass concentration in different layers of sand bed which is responsible for head loss was quantified followed by determining the inactivation potential and biological activity in different layers of sand bed.The biomass concentration was determined by measuring Adenosine Triphosphate(ATP) content and biological activity by using combination of total cell count and ATP of the sand samples in both column and full scale SSF. Inactivation potential of different layers of sand bed was determined by carrying of spiking experiments after removal of different layer of sand bed. Spiking experiments were done only in columns SSF. Spatial Distribution of biomass on the filter bed was also investigated. In order to accelerate the growth of microorganism’s, three possible solutions were investigated in column SSF. First was the use of additional nutrients, second was to increase the filtration rate and third was the use of microbial inoculum (schmutzdecke) from a matured filter. The effect of different operational parameters on the efficacy of column SSF was determined by measuring influent and effluent parameters such as particle counts, turbidity, dissolved organic carbon and total nitrogen. Along with this spiking experiment of E.Coli WR1 and MS2 bacteriophage were carried out during stages of filter operation. Physical, chemical & microbialparameters that were used to assess the efficacy of SSF were correlated to each other and most suitable indicators of ripening were identified. In total there were 8 columns, running in duplicates with six of them running at filtration rate of 0.1 m/hrand two at 0.5m/hr. Two columns with 0.1 m/hr were used a reference for comparison. Two columns running at 0.1 m/hr were seeded with microbial inoculum from one of the full scale filters and other two at 0.1 m/hr were seeded with additional nutrients.The Biomass concentration decreased with depth in both the full scale and column slow sand filters. More than 80% of biomassaccumulation takes place in schmutzdecke and top 2 cm of sand bed. Position of the inlet valve source affects the spatial distribution of biomass on the filter surface due to lateral gradients and leads to uneven biomass growth. Cell Count follows the similar patters as biomass distribution. Biological activity was present throughout the 10 cm of sand bed. Decimal Elimination Capacity of column SSF decreased after the removal of subsequent sand layers, with most significant reduction in DEC was observed after the removal of schmutzdecke (>1 log). Columnwith added microbial inoculum were able to mimic the full scale filters. After removing of schmutzdecke and top 2 cm of sand bed where most of the biomassaccumulation takes place, columns were still able to achieve more than 3 logremovals for bacteria and 1 log for virus. This is higher than the values required by current full scale SSF’s in their operation. Effluent turbidity and particle counts wereless than 0.1 NTU and 200/ml even after the removal of schmutzdecke in columns with inoculum. Combining the results of the biomassdistribution and spiking experiments carried out in the columns with microbialinoculum, it can be concluded that ripening period of the SSF will bedrastically reduced if the scraping of only 4 cm of sand bed takes place including schmutzdecke. To reduce the start up time of a new filter, addition of microbial inoculum (schmutzdecke from a matured filter) is the better solution in comparison to addition of nutrients or increasing the filtration rate. Although the purpose of adding inoculum or nutrients or increasing the filtration rate was same: that is to increase the biological activity in the sand bed. Columns with inoculum reached more than 2.5 log removals in first 30 days of operation as compared to others which have less than 1.85 log and took only 24and 27 days to reach median levels of turbidity of 0.1 NTU and particle count of less than 200/ml. Reductions of bacteria, viruses, turbidity and particle counts increase substantially with time as filters ripens. No such pattern was observed in the DOC and TN removal, they were more a function of the influent water quality and independent of the ripening period. Correlation between different water quality parameters resulted Particle count and turbidity can be used as indicators of ripening. Although particle count was a better surrogate than turbidity as an indicator of ripening, using them together would provide a better insight as the correlation between them increases as the filter ripens. DOC and TN cannot be used as indicators of ripening. </p
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