Audiologic monitoring of multi-drug resistant tuberculosis patients on aminoglycoside treatment with long term follow-up

<p>Abstract</p> <p>Background</p> <p>Multi-drug resistant tuberculosis has emerged as a significant problem with the resurfacing of tuberculosis and thus the need to use the second line drugs with the resultant increased incidence of adverse effects. We discuss the effect of second line aminoglycoside anti-tubercular drugs on the hearing status of MDR-TB patients.</p> <p>Methods</p> <p>Sixty four patients were put on second line aminoglycoside anti-TB drugs. These were divided into three groups: group I, 34 patients using amikacin, group II, 26 patients using kanamycin and group III, 4 patients using capreomycin.</p> <p>Results</p> <p>Of these, 18.75% of the patients developed sensorineural hearing loss involving higher frequencies while 6.25% had involvement of speech frequencies also. All patients were seen again approximately one year after aminoglycoside discontinuation and all hearing losses were permanent with no threshold improvement.</p> <p>Conclusion</p> <p>Aminoglycosides used in MDR-TB patients may result in irreversible hearing loss involving higher frequencies and can become a hearing handicap as speech frequencies are also involved in some of the patients thus underlining the need for regular audiologic evaluation in patients of MDR-TB during the treatment.</p

Study Of Human Activity In Video Data With An Emphasis On View-invariance

The perception and understanding of human motion and action is an important area of research in computer vision that plays a crucial role in various applications such as surveillance, HCI, ergonomics, etc. In this thesis, we focus on the recognition of actions in the case of varying viewpoints and different and unknown camera intrinsic parameters. The challenges to be addressed include perspective distortions, differences in viewpoints, anthropometric variations, and the large degrees of freedom of articulated bodies. In addition, we are interested in methods that require little or no training. The current solutions to action recognition usually assume that there is a huge dataset of actions available so that a classifier can be trained. However, this means that in order to define a new action, the user has to record a number of videos from different viewpoints with varying camera intrinsic parameters and then retrain the classifier, which is not very practical from a development point of view. We propose algorithms that overcome these challenges and require just a few instances of the action from any viewpoint with any intrinsic camera parameters. Our first algorithm is based on the rank constraint on the family of planar homographies associated with triplets of body points. We represent action as a sequence of poses, and decompose the pose into triplets. Therefore, the pose transition is broken down into a set of movement of body point planes. In this way, we transform the non-rigid motion of the body points into a rigid motion of body point iii planes. We use the fact that the family of homographies associated with two identical poses would have rank 4 to gauge similarity of the pose between two subjects, observed by different perspective cameras and from different viewpoints. This method requires only one instance of the action. We then show that it is possible to extend the concept of triplets to line segments. In particular, we establish that if we look at the movement of line segments instead of triplets, we have more redundancy in data thus leading to better results. We demonstrate this concept on “fundamental ratios.” We decompose a human body pose into line segments instead of triplets and look at set of movement of line segments. This method needs only three instances of the action. If a larger dataset is available, we can also apply weighting on line segments for better accuracy. The last method is based on the concept of “Projective Depth”. Given a plane, we can find the relative depth of a point relative to the given plane. We propose three different ways of using “projective depth:” (i) Triplets - the three points of a triplet along with the epipole defines the plane and the movement of points relative to these body planes can be used to recognize actions; (ii) Ground plane - if we are able to extract the ground plane, we can find the “projective depth” of the body points with respect to it. Therefore, the problem of action recognition would translate to curve matching; and (iii) Mirror person - We can use the mirror view of the person to extract mirror symmetric planes. This method also needs only one instance of the action. Extensive experiments are reported on testing view invariance, robustness to noisy localization and occlusions of body points, and action recognition. The experimental results are very promising and demonstrate the efficiency of our proposed invariants. i

Operations Research Modeling of Cyclic Train Timetabling, Cyclic Train Platforming, and Bus Routing Problems

Public transportation or mass transit involves the movement of large numbers of people between a given numbers of locations. The services provided by this system can be classified into three groups: (i) short haul: a low-speed service within small areas with high population; (ii) city transit: transporting people within a city; and (iii) long haul: a service with long trips, few stops, and high speed (Khisty and Lall, 2003). It can be also classified based on local and express services. The public transportation planning includes five consecutive steps: (i) the network design and route design; (ii) the setting frequencies or line plan; (iii) the timetabling; (iv) the vehicle scheduling; and (v) the crew scheduling and rostering (Guihaire and Hao, 2008; Schöbel, 2012). The first part of this dissertation considers three problems in passenger railway transportation. It has been observed that the demand for rail travel has grown rapidly over the last decades and it is expected that the growth continues in the future. High quality railway services are needed to accommodate increasing numbers of passengers and goods. This is one of the key factors for economic growth. The high costs of railway infrastructure ask for an increased utilization of the existing infrastructure. Attractive railway services can only be offered with more reliable rolling stock and a more reliable infrastructure. However, to keep a high quality standard of operations, smarter methods of timetable construction are indispensable, since existing methods have major shortcomings. The first part of this dissertation, comprising Chapters 1-6, aims at developing a cyclic (or periodic) timetable for a passenger railway system. Three different scenarios are considered and three mixed integer linear programs, combined with heuristics for calculating upper and lower bounds on the optimal value for each scenario, will be developed. The reason of considering a periodic timetable is that it is easy to remember for passengers. The main inputs are the line plan and travel time between and minimum dwell time at each station. The output of each model is an optimal periodic timetable. We try to optimize the quality of service for the railway system by minimizing the length of cycle by which trains are dispatched from their origin. Hence, we consider the cycle length as the primary objective function. Since minimizing travel time is a key factor in measuring service quality, another criterion--total dwell time of the trains--is considered and added to the objective function. The first problem, presented in Chapter 3, has already been published in a scholarly journal (Heydar et al., 2013). This chapter is an extension of the work of Bergmann (1975) and is the simplest part of this research. In this problem, we consider a single-track unidirectional railway line between two major stations with a number of stations in between. Two train types--express and local--are dispatched from the first station in an alternate fashion. The express train stops at no intermediate station, while the local train should make a stop at every intermediate station for a minimum amount of dwell time. A mixed integer linear program is developed in order to minimize the length of the dispatching cycle and minimize the total dwell time of the local train at all stations combined. Constraints include a minimum dwell time for the local train at each station, a maximum total dwell time for the local train, and headway considerations on the main line an in stations. Hundreds of randomly generated problem instances with up to 70 stations are considered and solved to optimality in a reasonable amount of time. Instances of this problem typically have multiple optimal solutions, so we develop a procedure for finding all optimal solutions of this problem. In the second problem, presented in Chapter 4, we present the literature\u27s first mixed integer linear programming model of a cyclic, combined train timetabling and platforming problem which is an extension of the model presented in Chapter 3 and Heydar et al. (2013). The work on this problem has been submitted to a leading transportation journal (Petering et al., 2012). From another perspective, this work can be seen as investigating the capacity of a single track, unidirectional rail line that adheres to a cyclic timetable. In this problem, a set of intermediate stations lies between an origin and destination with one or more parallel sidings at each station. A total of T train types--each with a given starting and finishing point and a set of known intermediate station stops--are dispatched from their respective starting points in cyclic fashion, with one train of each type dispatched per cycle. A mixed integer linear program is developed in order to schedule the train arrivals and departures at the stations and assign trains to tracks (platforms) in the stations so as to minimize the length of the dispatching cycle and/or minimize the total stopping (dwell) time of all train types at all stations combined. Constraints include a minimum dwell time for each train type in each of the stations in which it stops, a maximum total dwell time for each train type, and headway considerations on the main line and on the tracks in the stations. This problem belongs to the class of NP-hard problems. Hundreds of randomly generated and real-world problem instances with 4-35 intermediate stations and 2-11 train types are considered and solved to optimality in a reasonable amount of time using IBM ILOG CPLEX. Chapter 5 expands upon the work in Chapter 4. Here, we present a mixed integer linear program for cyclic train timetabling and routing on a single track, bi-directional rail line. There are T train types and one train of each type is dispatched per cycle. The decisions include the sequencing of the train types on the main line and the assignment of train types to station platforms. Two conflicting objectives--(1) minimizing cycle length (primary objective) and (2) minimizing total train journey time (secondary objective)--are combined into a single weighted sum objective to generate Pareto optimal solutions. Constraints include a minimum stopping time for each train type in each station, a maximum allowed journey time for each train type, and a minimum headway on the main line and on platforms in stations. The MILP considers five aspects of the railway system: (1) bi-directional train travel between stations, (2) trains moving at different speeds on the main line, (3) trains having the option to stop at stations even if they are not required to, (4) more than one siding or platform at a station, and (5) any number of train types. In order to solve large scale instances, various heuristics and exact methods are employed for computing secondary parameters and for finding lower and upper bounds on the primary objective. These heuristics and exact methods are combined with the math model to allow CPLEX 12.4 to find optimal solutions to large problem instances in a reasonable amount of time. The results show that it is sometimes necessary for (1) a train type to stop at a station where stopping is not required or (2) a train type to travel slower than its normal speed in order to minimize timetable cycle time. In the second part of this dissertation, comprising Chapters 7-9, we study a transit-based evacuation problem which is an extension of bus routing problem. This work has been already submitted to a leading transportation journal (Heydar et al., 2014). This paper presents a mathematical model to plan emergencies in a highly populated urban zone where a certain numbers of pedestrians depend on transit for evacuation. The proposed model features a two-level operational framework. The first level operation guides evacuees through urban streets and crosswalks (referred to as the pedestrian network ) to designated pick-up points (e.g., bus stops), and the second level operation properly dispatches and routes a fleet of buses at different depots to those pick-up points and transports evacuees to their destinations or safe places. In this level, the buses are routed through the so-called vehicular network. An integrated mixed integer linear program that can effectively take into account the interactions between the aforementioned two networks is formulated to find the maximal evacuation efficiency in the two networks. Since the large instances of the proposed model are mathematically difficult to solve to optimality, a two-stage heuristic is developed to solve larger instances of the model. Over one hundred numerical examples and runs solved by the heuristic illustrate the effectiveness of the proposed solution method in handling large-scale real-world instances

Beyond Gingles: influence districts and the pragmatic tradition in voting rights law

Should minority voters who are not numerous enough to form.a majority of an electoral district have a legal right to protection against vote dilution? This question of "influence districts" is not new, but has yet not been definitely resolved by judicial decisions. This paper examines the logic, history, and law related to influence districts. Any proposal for a legal stance on the question of influence districts should continue the dominant line of tradition of Congress and the courts, rather than contravene it. Therefore, after an introduction. Section II of this paper traces what I term the "practical" or "pragmatic" tradition in voting rights law from the passage of the Reconstruction Constitutional Amendments through the 1982 amendments to the Voting Rights Act and the nearly simultaneously-issued U.S. Supreme Court decision in Rogers v. Lodge. Beginning in 1870, Congress and later. the courts, rejected an abstract, formulaic, "bright-line" approach to voting rights law except during the period of massive discrimination and disfranchisement. Both Congress and the Supreme Court went beyond protecting the bare right of members of minority groups to vote. Instead. they realized that to cast an effective vote, African-Americans and others had to be sheltered from violence, intimidation, and fraud, and they had to be free to speak and organize. In the 1940s, courts insisted on nondiscrimination in primaries, and in the late 1960s, they helped guarantee the right to be free of recently established discriminatory electoral structures. The courts and Congress refused to accept two proffered bright lines: one drawn, in effect, between voting per se and everything else, and the other guaranteeing proportional representation. Rather. they adopted the less precise. but more nuanced "totality of the circumstances" test for proving both intent and effect. In Section III of the paper. I discuss the three-pronged test outlined in Thornburg v. Gingles. Even though Gingles is sometimes interpreted to imply that courts need pay no attention to minority groups that cannot form effective majorities of electoral districts, I point out that Justice Brennan's opinion in Gingles specifically refuses to foreclose that question and argue that both the log1ic of the opinion a.d contemporary political experience contravene the alleged implication. More specifically, I suggest that it is wrong for courts to isolate the first prong of the Gingles test from the other two. Viewed as interconnected, the three parts of the test do not preclude a consideration of the question of influence districts. Indeed. election data from both hypothetical and actual examples demonstrates that. there is no possible theoretical division between influence districts and control districts. I conclude that there is no bright line in Gingles. Section IV of the paper takes a very brief look at some federal court op1111Ons concerning influence districts. concentrating on the Garza, Armour, and Springfield Park District cases. Their diverse analyses and criticisms that can be made of them suggest two different, but more systematic approaches to the influence district problem - a "results" approach and an "intent" approach - which I flesh out in Section V. In both approaches, I concentrate on totality of the circumstances.standards, in line with the pragmatic tradition, the Congress's intent in extending and amending the Voting Rights Act in 1982, and the Supreme Court's decisions in White v. Regester and Rogers v. Lodge. Finally, I attempt to respond generally to criticisms of protecting the interests of small minority groups. I conclude that both the value of bright-line standards and the dangers of relaxing them have been exaggerated

ML-based Approaches for Wireless NLOS Localization: Input Representations and Uncertainty Estimation

The challenging problem of non-line-of-sight (NLOS) localization is critical for many wireless networking applications. The lack of available datasets has made NLOS localization difficult to tackle with ML-driven methods, but recent developments in synthetic dataset generation have provided new opportunities for research. This paper explores three different input representations: (i) single wireless radio path features, (ii) wireless radio link features (multi-path), and (iii) image-based representations. Inspired by the two latter new representations, we design two convolutional neural networks (CNNs) and we demonstrate that, although not significantly improving the NLOS localization performance, they are able to support richer prediction outputs, thus allowing deeper analysis of the predictions. In particular, the richer outputs enable reliable identification of non-trustworthy predictions and support the prediction of the top-K candidate locations for a given instance. We also measure how the availability of various features (such as angles of signal departure and arrival) affects the model's performance, providing insights about the types of data that should be collected for enhanced NLOS localization. Our insights motivate future work on building more efficient neural architectures and input representations for improved NLOS localization performance, along with additional useful application features.Comment: This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessible. Work partly supported by the RA Science Committee grant No. 22rl-052 (DISTAL) and the EU under Italian National Recovery and Resilience Plan of NextGenerationEU on "Telecommunications of the Future" (PE00000001 - program "RESTART"

Social Environment and Genetics as Determinants of Depression Occurrence and Its Chronicity: A Longitudinal Survey

Depressive disorders are a set of heterogeneous disorders who se common characteristics are sadness and lack of interest, but varying regarding other symptoms, response to treatment and probability of recurrence and chronicity. They are a serious public health problem due to high prevalence and disability burden . Dep ression has a multifactorial causality with several genetic, behavioral and environmental factors playing a putative causal role . Thus, the aim of this thesis wa s to elucidate the interwoven effects of some environmental stressors, individual’s characteristics and some genetic factors on the occurrence and the course of depressive disorders. T he subjects were drawn from the PART study (In Swedish: Psykisk hälsa, A rbete och RelaTioner), a longitudinal study with three waves between 1998 and 2010, focused on mental health, work and relations among adult people residing in the Stockholm County, Sweden . In S tudies I and III, the relationship between polymorphisms in C OMT and serotonin transporter genes and depressive disorders were explored using a case - control approach. Ge ne x environment interaction effect s on depression risk were addressed focusing on COMT gene, childhood adversit ies and stressful life event s in Stu dy I ; and focusing on serotonin transporter gene and objective life events (i.e. loss/separation ) in Study III. Significant interactions were found between COMT and family problems during childhood and between serotonin transporter and partner’s loss/ separ ation. In Study II, the association between the psychosocial work environment and depression was scrutinized in a follow - up design of people employed in the same job over three - years . T he results showed a strong relationship between inadequate social climate and major depression among women three - years later , while there were no certain effects for the remaining exposure variables. Among men, the findings were controversial : high job demands and inadequate skill discretion appeared as protective factor s against depression ; thus, more studies using a similar approach are warranted. In Study IV, the complex inter - relationships among personal characteristics and circumstances over different life periods , and their effects on the chronicity of depression , were explored in a follow - up study of depressed subjects over ten years . It was analyzed using structural equation modeling (SEM). The resulting model revealed two main mechanisms anchored on personality traits: an internalizing pathway and an externalized /adversity pathway ; which are in line with studies about the onset of depression. The effort in this doctoral thesis consisted in putting together some pieces of a big puzzle. It is necessary to develop integrative models from different disciplines (e.g. genetics, neurosciences and epidemiology) in order to elucidate the complex mechanisms behind the depressive disorders

Anytime Heuristic for Weighted Matching Through Altruism-Inspired Behavior

We present a novel anytime heuristic (ALMA), inspired by the human principle of altruism, for solving the assignment problem. ALMA is decentralized, completely uncoupled, and requires no communication between the participants. We prove an upper bound on the convergence speed that is polynomial in the desired number of resources and competing agents per resource; crucially, in the realistic case where the aforementioned quantities are bounded independently of the total number of agents/resources, the convergence time remains constant as the total problem size increases. We have evaluated ALMA under three test cases: (i) an anti-coordination scenario where agents with similar preferences compete over the same set of actions, (ii) a resource allocation scenario in an urban environment, under a constant-time constraint, and finally, (iii) an on-line matching scenario using real passenger-taxi data. In all of the cases, ALMA was able to reach high social welfare, while being orders of magnitude faster than the centralized, optimal algorithm. The latter allows our algorithm to scale to realistic scenarios with hundreds of thousands of agents, e.g., vehicle coordination in urban environments

Asymptotic behavior and control of a "guidance by repulsion" model

Electronic version of an article published as Mathematical Models and Methods in Applied Sciences 30.04 (2020): 765-804, https://doi.org/10.1142/S0218202520400047 © 2020 World Scientific Publishing CompanyWe model and analyze a guiding problem, where the drivers try to steer the evaders' positions toward a target region while the evaders always try to escape from drivers. This problem is motivated by the guidance-by-repulsion model [R. Escobedo, A. Ibañez and E. Zuazua, Optimal strategies for driving a mobile agent in a guidance by repulsion model, Commun. Nonlinear Sci. Numer. Simul. 39 (2016) 58-72] where the authors answer how to control the evader's position and what is the optimal maneuver of the driver. First, we analyze well posedness and behavior of the one-driver and one-evader model, assuming of the same friction coefficients. From the long-time behavior, the exact controllability is proved in a long enough time horizon. Then, we extend the model to the multi-driver and multi-evader case. We assumed three interaction rules in the context of collective behavior models: flocking between evaders, collision avoidance between drivers and repulsive forces between drivers and evaders. These interactions depend on the relative distances, and each agent is assumed to be undistinguishable and obtained an averaged effect from the other individuals. In this model, we develop numerical simulations to systematically explore the nature of controlled dynamics in various scenarios. The optimal strategies turn out to share a common pattern to the one-driver and one-evader case: the drivers rapidly occupy the position behind the target, and want to pursuit evaders in a straight line for most of the time. Inspired by this, we build a feedback strategy which stabilizes the direction of evadersThis project has received funding from the European Research Council (ERC) under the Euro-pean Union’s Horizon 2020 research and innovation programme (grant agreement No. 694126-DyCon). The work of the first author has been supported by CNCS-UEFISCDI Grant No. PN-III-P4-ID-PCE-2016-0035. The work of the second author has been funded by the Alexander von Humboldt-Professorship program, the European Union’s Horizon 2020 research andinnovation programme under the Marie Sklodowska-Curie grant agreement No.765579-ConFlex, grant MTM2017-92996-C2-1-R COSNET of MINECO (Spain), ELKARTEK project KK-2018/00083 ROAD2DC of the Basque Government, ICON of the French ANR and Nonlocal PDEs: Analysis, Control and Beyond, AFOSR Grant FA9550-18-1-024

A community Based Child Drowning Prevention Program in Bangladesh: a model for low income countries

Background: Drowning is a global public health problem of children. Children of low- and middle-income countries are the most susceptible victims. Prevention measures implemented in high-income countries have effectively reduced drowning. However, in low- and middle-income countries, due to a severe lack of information, drowning has not been recognized as a child survival issue. Moreover, prevention efforts remain non-existent as there is no proven effective measure applicable for these countries, including Bangladesh. Objectives: The objectives of the research activities were to determine the current child drowning situation and risk-factors in rural areas of Bangladesh (Paper I); to understand the community perception of drowning problems and the possible solutions for designing a preventive programme in the rural area of Bangladesh (Paper II); to develop, pilot and assess initial community response to an intervention package in terms of acceptability, feasibility and sustainability (Paper III) and to evaluate the package for its effectiveness (Paper IV). Methods: A cross sectional survey and a case-control study were conducted to determine the magnitude and identify risk-factors of child drowning respectively (Paper I). Community perception on drowning prevention was explored by using a qualitative method (Paper II). Intervention measures were identified through workshops with the relevant stakeholders. Utilizing qualitative methods community acceptability, feasibility and sustainability of the intervention package were initially assessed (Paper III). A quasi-experimental design was used to evaluate the effectiveness of the intervention package (Paper IV). Two sub-districts were selected each having a population of 200,000. One was allocated as an intervention area and the other as a comparison area. Quantitative data was collected through structured pre-tested questionnaires and the qualitative data was gathered through Focus Group Discussions (FDGs) and in-depth interviews. Results: The drowning rate of Bangladeshi rural children aged 1-4 years was found to be 156.4 per 100,000 (95% CI 138.5 - 176.6 per 100,000). The proportional mortality due to drowning in the children was about 28.0 percent. Natural water bodies were the most frequent places of drowning, and over 40 percent occurred in ponds. The child's sex, mother's age and literacy, family income and ownership of agricultural land by the families were identified as risk factors (Paper I). Community people wrongly perceive that children 5 - 10 years are at the greatest risk of drowning. Participants of the FGDs, parents, adolescents and community leaders, knew the common causes of drowning and were able to mention a few preventive measures. However, they do not act on this knowledge (Paper II). Increased supervision of children through the creation of drowning-safe homes and the establishment of community crèches, raising water safety awareness, and educating the community on first response skills were the three core aspects identified through workshops to include in the intervention package. Qualitative study revealed that these measures are accepted by the community, feasible and sustainable (Paper III). After three years of implementation of the intervention package the evaluation showed that 36 percent of households became drowning safe and through 100 community crèches 2,680 children aged 1-4 years were kept safe under direct supervision. Nearly all the population of the intervention area were reached through various behaviour change communication materials. In the intervention area fatal drowning rate declined from 120.8 to 53.7 per 100,000; however, in the comparison area the rate remained the same in the base-line and the end-line data (Paper IV). Conclusion: Drowning is one of the major survival issues among children aged 1-4 years in rural Bangladesh. The intervention model developed through these research activities was found to be effective in reducing child drowning. Improved supervision, creating a heightened water safety culture of the community and utilizing low cost locally available resources are the fundamental intervention strategies identified in reducing child drowning in rural Bangladesh. This model is developed in such a way that it could be applicable in similar low-income settings

Arsenic removal by iron based co-precipitation : Mechanisms in groundwater treatment

Arsenic (As) contamination of groundwater with is a wide-scale problem, affecting health of people around the world. The World Health Organization (WHO) guideline for As in drinking water is currently set at 10 &micro;g/L, however recent studies suggest that As can cause a considerable damage to human health even at concentrations lower than the WHO guideline. As a result, several drinking water companies are making efforts to reduce As concentrations in drinking water to very low concentrations, below 1 &micro;g/L.&nbsp; Co-precipitation of As with iron(III)(oxyhydr)oxides [Fe(III)(oxyhydr)oxides] is a widely used As removal method in groundwater treatment. Fe(III)(oxyhydr)oxides are produced in an As contaminated water, typically by oxidation of naturally occurring ferrous iron [Fe(II)] in groundwater using oxygen (O2) and/or dosing a ferric iron [Fe(III)] coagulant such as Ferric Chloride (FeCl3). Arsenic strongly adsorbs to the surface of freshly formed Fe(III) precipitates and subsequently the As bearing Fe(III) precipitates are removed by filtration to produce As-safe water. The adsorption efficiency of As onto Fe(III) precipitates and the size of As bearing Fe(III) particles is governed by several interdependent factors such as the conditions of Fe(III)(oxyhydr)oxide generation in water, oxidation state of As, solution pH and the concentration of As and co-occurring ions with respect to Fe in the initial solution. The objective of this thesis is to discern mechanistic understanding of As removal by co-precipitation with Fe(III)(oxyhydr)oxides under different redox, ion composition and filtration conditions and to investigate routes to reduce As in drinking water to very low levels, below 1 &micro;g/L. We carried out sampling campaigns at water treatment plants in the Netherlands to gain understanding of the pertinent As removal mechanisms during groundwater treatment. It was found that rapid sand filtration is the most important treatment step for oxidation and removal of As during groundwater treatment. The removal of As is tightly coupled to Fe removal in rapid sand filters and mainly attributed to co-precipitation of As with Fe(III)(oxyhydr)oxides, which are generated by oxidation and subsequent hydrolysis of Fe(II). The As co-precipitation efficiency with Fe(III)(oxyhydr)oxides is much higher in rapid sand filter beds compared to aeration and supernatant storage. This is ascribed to oxidation of arsenite [As(III)] to arsenate [As(V)] in the rapid sand filter beds, potentially executed by manganese oxides (MnO2) and/or As(III) oxidizing bacteria, as both are observed in the coating of rapid sand filter media grains. In the pH range of most groundwaters, As(V) adsorbs to Fe(III)(oxyhydr)oxides much more effectively than As(III). Typical aeration techniques such as cascades are inefficient in oxidizing As(III) to As(V) before rapid sand filters at water treatment plants, resulting in inefficient As co-precipitation with Fe(III)(oxyhydr)oxides. Nevertheless, dosing a strong oxidant such as potassium permanganate (KMnO4) rapidly accomplishes As(III) oxidation to As(V) and drastically improves As co-precipitation efficiency with Fe(III)(oxyhydr)oxides, resulting in As reduction to very low levels, below 1 &micro;g/L. While no negative effect on the removal efficiency of Fe(II), Mn(II) and ammonium (NH4+) in rapid sand filters is observed due to KMnO4 dosing, the pre-established Fe(II) and Mn(II) removal mechanisms in rapid sand filters are altered due to KMnO4 dosing, generating a need for rapid sand filter media replacement. We also found that dosing of strong oxidants during groundwater treatment impacts the composition and structure of the formed Fe and Mn bearing precipitates. For example, in the absence of competing ions, O2 produces Mn(III)-incorporated moderately crystalline lepidocrocite, sodium hypochlorite (NaOCl) produces Mn(III)-incorporated poorly-ordered hydrous ferric oxide, and KMnO4 produces poorly-ordered MnO2 and poorly-ordered hydrous ferric oxide phases. This diversity of formed precipitates under different redox conditions should be considered in As removal during groundwater treatment. In this thesis we show that As levels below 1 &micro;g/L can alternatively be achieved by dosing a small amount of FeCl3 in the effluent of rapid sand filter at groundwater treatment plants. The effluent of rapid sand filter predominantly contains arsenate [As(V)] which is much more effectively adsorbed to Fe(III)(oxyhydr)oxides than As(III). In this way use of KMnO4 or other strong oxidants can be avoided at groundwater treatment plants. Nevertheless, the ionic composition of water strongly controls As(V) removal by iron based co-precipitation, by affecting the adsorption efficiency of As(V) with Fe(III)(oxyhydr)oxides and the size of As bearing Fe(III) particles. We show that silicate (SiO4-4) and phosphate (PO4-3) reduce As(V) removal, mainly due to competition with As(V) adsorption to Fe(III) precipitates. Though SiO4-4 en PO4-3 oxyanions are known to strongly reduce Fe(III) precipitate growth, we show that presence of high calcium (Ca) concentrations in groundwater (common in the Netherlands and several other parts of the world) counteracts the negative effects of both SiO4-4 en PO4-3 and promote coagulation of Fe(III) precipitates to form large particles which are easily separated from water by gravitation settling and rapid sand filtration. Despite presence of high Ca concentrations, Natural Organic Matter (NOM) reduces As(V) removal quite drastically, attributed largely to the formation of soluble and colloidal Fe(III)&ndash;NOM complexes which are not easily separated by conventional filtration. In-line dosing of a small amount of FeCl3 in the feed water of ultrafiltration (UF) step (typically used for final polishing and disinfection) is shown to be effective for As reduction to &lt;1 &micro;g/L at water treatment plants which use artificially recharged water as source. In this process, As(V) co-precipitation with Fe(III)(oxyhydr)oxides rapidly reaches equilibrium, thus little contact time before the membranes is required. Moreover, when As bearing Fe(III) precipitates grow to sizes larger than the pore size of UF membranes (expected for most Ca bearing groundwaters) the Fe(III) particles foul the membranes mainly by forming a cake-layer on the surface which is effectively removed with a hydraulic backwash. Thus, we conclude that sustainable long term operation of UF membranes with in-line FeCl3 dosing for As removal is highly viable. Based on the present work, three groundwater treatment plants in the Netherlands have received an upgrade with KMnO4 dosing for reducing As to below 1 &micro;g/L. Another treatment plant, which makes use of artificially recharged groundwater, will receive an upgrade with FeCl3 dosing before the polishing UF step