1,721,006 research outputs found
Content and Treatment of Trace Elements and Organic Micropollutants in Tunnel Wash Water
Full text linkVehicular traffic is a significant source of pollution to the environment. Pollutants are released along the roads and can be transported further away due to wind and rain. Tunnels are road constructions that accumulate considerable amounts of traffic pollution due to them being enclosed structures protected from the effects of the weather. To maintain safety and increase the lifetime of the tunnels, they are washed regularly, especially in urban areas with high traffic loads. This cleaning process produces tunnel wash water (TWW), a highly contaminated water matrix containing all the contaminants that were once on the tunnel interior. Previous investigations of TWW content have revealed high concentrations of trace elements and polycyclic aromatic hydrocarbons (PAHs), with some additional interest in tyrerelated contaminants in recent years. Still, knowledge is lacking on the presence of other organic micropollutants, such as per- and polyfluoroalkyl substances (PFASs), benzothiazoles (BTHs), benzotriazoles (BTRs), bisphenols (BPs), and benzophenones (BzPs), already established in road and parking lot runoff. Nowadays, treatment of TWW is required before release into the environment. The standard treatment of TWW today is sedimentation. However, in areas with high traffic loads, the pollution concentrations are suspected to be too high for sedimentation basins to handle alone, especially for dissolved contaminants not removed during sedimentation. Alternative treatments further improving TWW quality have only been tested in lab-scale experiments, while realistic situation field experiments over an extended period are lacking. Additionally, a better understanding of the overall biological effects of TWW for specific toxicological endpoints and how these are changing during treatment is missing. This is needed to optimise treatment strategies and ensure a low impact on receiving water bodies.
Therefore, this thesis aims to investigate different treatment technologies for removing trace elements, organic micropollutants, and biological effects from TWW.
TWW sampling and field experiments with alternative treatments were conducted in the Bjørnegård tunnel outside of Oslo, Norway. It is fitted with two indoor sedimentation basins as primary treatment and a pilot for secondary treatment. The pilot includes bag filtration, microfiltration with a ceramic membrane, and a granular activated carbon (GAC) filtration column. Ten trace elements and 48 out of 78 analysed organic micropollutants were detected in the TWW. Many of these compounds have been established as toxic to exposed organisms. 15 compounds have been categorised as having a very high persistent, mobile, and toxic (PMT) score. These are highly problematic to release into the environment and difficult to remove by conventional water treatment. Several trace elements were detected in the highest concentrations on the particles compared to the dissolved fraction. In contrast, most organic compounds, except PAHs, were mainly found in the dissolved fraction.
Sedimentation had the most significant impact on particles and particle-associated contaminants but only a minor effect on the dissolved compounds. Additional membrane filtration reduced particles and a few particle-associated trace elements but did not affect particle-associated micropollutants. A significant improvement in dissolved micropollutants was only observed after the GAC filtration. This is attributed to GAC’s ability to adsorb dissolved compounds to the surface. The biological effects of the dissolved fraction of untreated TWW exceeded the regulatory effect-based trigger (EBT) values. The membrane filtration showed the best result for both AhR activation (indicating potential carcinogenic effects) and oxidative stress response for the particulate fraction. In both cases, the effect was reduced to below the detection limit for the specific bioassay. GAC filtration significantly reduced the AhR activation and neurite outgrowth inhibition caused by the dissolved fraction samples to below regulatory EBTs in all cases, indicating successful treatment.
GAC was identified as the most effective secondary treatment method for the pollutants detected, especially for the dissolved micropollutants. This project has shown that by implementing GAC in the TWW treatment, the levels of persistent and toxic compounds released into the environment can be significantly reduced compared to the current standard treatment. A recommended approach involves using sedimentation for primary treatment followed by GAC filtration, with suggested modifications. The need for stationary treatment solutions or the potential for mobile treatment systems should be evaluated. Future dis-charge permits should incorporate ∑PFAS24, BTR, TTR, BTH, 2-OH-BTR, and effect-based methods to improve the water quality data and TWW treatment evaluation. Further investigations are necessary to elucidate the impact of detergents on organic micropollutant distribution and treatment efficiency. Future research should focus on testing effect-based methods for TWW monitoring, potentially expanding the assay repertoire and employing iceberg modelling to assess compound contributions to observed effects. Additionally, microplastics and emerging organic micropollutants should be prioritised in the list of parameters to evaluate TWW treatment.Fulltext not availabl
Removal of organic pollutants from landfill leachate by electrochemical oxidation - Assessment of performance and applicability in Northern Norway
Full text linkLandfill leachate treatment by advanced oxidation processes has gained much attention in the past decades. The removal of organic pollutants from landfill leachate in particular has been in focus due to their detrimental effects on the environment. This fact also leads to increasingly stringent regulations put in place by the authorities regarding the pollutant removal and adherence to treatment goals. More stringent regulations for landfill leachate treatment are also expected to be effective in Norway in the near future. The new regulations contain a list of priority substances that need to be removed below their detection limit in order to release the effluent after treatment into nearby waterbodies. An appropriate treatment process that is able to accomplish the treatment goals and takes the given local climate conditions into consideration is required. Low average temperatures in subarctic climates provide a significant challenge.
The motivation of the present thesis was to find a suitable landfill leachate treatment process that is able to remove priority substances while withstanding cold operating temperatures. An extended literature study was the basis for choosing electrochemical oxidation, an advanced oxidation process, as a suitable treatment process. The majority of electrochemical oxidation studies have been carried out at room or elevated temperatures, while there is a lack of focus on wastewater treatment in cold climates. Furthermore, none assessed the application of advanced oxidation processes. This thesis bridges this knowledge gap and contributes to the applied field of electrochemistry by assessing its applicability under cold operating temperatures. The work is therefore of great interest in light of the increased focus on the technology in arctic regions.
This thesis consists of three separate studies:
1. A mechanistic study that helps to understand the ongoing different oxidation processes during the electrochemical oxidation of organic pollutants.
2. A laboratory scale study with a model organic pollutant from the priority list where the influence of different parameters on its oxidation was assessed, with a special focus on temperature.
3. A laboratory scale study with pre-treated landfill leachate that contains the same model organic pollutant, where the matrix effect and more applied parameters were assessed under cold climate conditions.
The mechanistic study of the model pollutant salicylic acid confirmed that three different oxidation pathways take place during the electrochemical oxidation: Direct electron transfer from the pollutant to the electrode surface, electrochemical oxygen transfer reaction from hydroxyl radical to the organic pollutant, and mediated oxidation via an intermediately formed oxidant, such as active chlorine. Density functional and natural bond theory were able to successfully predict the salicylic acid intermediates that were formed during electrochemical oxidation.
In the second study, Bisphenol A (5 µM) was used as the model compound as it is listed on the Norwegian priority substance list. Complete removal of Bisphenol A was achieved at low temperatures (6 °C) with the major drawback of extended treatment times. Besides temperature, pH also had a significant effect on the removal of Bisphenol A, and an alkaline pH (10) was found to be favourable. The anode material was found to have a major impact on the formation of disinfection by-products, favouring perchlorate formation on BDD anodes and trihalomethanes on Pt.
The final study confirmed increased treatment times at low operating temperatures (6 °C). The study further showed that a relatively high current density (43 mA/cm2 ) has to be applied in order to achieve complete Bisphenol A removal (5 µM) from the landfill leachate. The matrix effect of the landfill leachate disclosed lower Bisphenol A degradation rates compared to the ones obtained in the second study in clean electrolyte (3.3 mM NaCl & 0.3 mM Na2SO4). Formation of disinfection by-products increased with the application of higher current densities (10 – 86 mA/cm2 ) and temperatures (6 – 20 °C) while the anode material influenced their nature as previously.
The results of the three studies show that electrochemical oxidation is able to remove Bisphenol A from landfill leachate under cold operating temperatures. Treatment goals regarding Bisphenol A, given by the Norwegian authorities, were satisfied and indicate that results are transferrable to other organic compounds on the priority list. The major drawback are the increased treatment times, which subsequently result in higher energy demands, and ultimately in higher costs. Norway is a country driven by hydropower and lower electricity prices than the rest of Europe, so electrochemical oxidation is still a sustainable and economically feasible choice. Attention has to be paid to the choice of electrode material as they are a major matter of expense as well as influencing the disinfection by-products that are formed. This work sets iii precedent with regards to applicability of electrochemical advanced oxidation processes under cold operating temperatures
NOM removal in drinking water treatment using dead-end ceramic microfiltration: Assessment of coagulation/flocculation pretreatment
No full textIn Nordic countries, surface water is a common source for potable water production. Such waters are often characterised by high Natural Organic Matter (NOM) content, resulting in high colour, very low turbidity, low alkalinity and low hardness due to natural conditions. Treatment of such waters basically comprises the removal of NOM and colour, corrosion control and disinfection. Although the largest part of NOM is not harmful, some fractions can cause colour, taste and odour problems or can even be toxic. Complexation of heavy metals and organic micro-pollutants, mobilizing them and making them available in the water phase, and increasing the amount of necessary disinfectants as well as being recognized as precursors for disinfection by-product formation which can be carcinogenic, are issues to be considered. In addition, there is a growing concern on the increase of NOM in natural water sources. Recent studies have shown that the concentration of NOM in surface water has increased in the last decades and may increase further during the coming decades, caused by progressing climate change issues and/or changed precipitation patterns. Thus, the removal of NOM is one of the major concerns and makes advanced drinking water treatment necessary.
In the past, conventional treatment processes such as coagulation/rapid sand filtration and filtration by nanofiltration (NF) membranes have been used successfully in Norway. However, a number of disadvantages have been identified in these processes. While the quality off effluent from rapid filters is high if coagulation is optimised, it may be severely compromised if coagulation fails, or operation is unstable. NF membranes have been subject to high irreversible fouling. High operating pressures at low fluxes, permeability loss over time and high chemical demands for cleaning have been observed frequently. By contrast, low pressure membrane filtration has emerged as an alternative for direct surface water treatment in recent years, with number of installations increasing rapidly around the world. Disadvantages as described above can be avoided to a large extent with this technology. The usage of low pressure membrane processes leads to high, stable effluent quality compared to conventional technologies, especially with regards to hygienic aspects since water borne parasites and most of bacteria can be retained. By applying ceramic microfiltration (MF) a more energy efficient operation is possible, the higher investment costs for ceramic membranes can be offset by the ability to operate with significantly higher fluxes. However, such membranes demand coagulation pre-treatment in order to achieve sufficient NOM and colour removal, fulfil the requirements as a hygienic barrier as well as for the control fouling by NOM.
This study showed that coagulation, combined with subsequent ceramic MF, is a successful concept for the direct treatment of Nordic waters. In spite of high NOM content in the raw water (DOC 6.8 mg C/L, colour 55 mg Pt/L), stable operation was demonstrated at high membrane fluxes of up to 250 L/(m2 h), achieving irreversible membrane fouling below 1 mbar/h, a DOC removal of 70% and colour removal of around 90%, at a coagulant dosage of 0.65 mg Al per mg DOC (using PACL at pH 6, with 60s of inline flocculation). While NOM removal depended only on coagulant dosage and coagulation pH, membrane fouling was also influenced by flocculation type, time and G-value. The study also found that the optimization of coagulation pretreatment is crucial. If, for example, an insufficient amount of coagulant is dosed, membrane fouling increases drastically, residual metal concentration is high and NOM removal is minimal. Inline coagulation with a static mixer, followed by pipe flocculation, showed promising results compared to conventional tank coagulation, where irreversible fouling rates observed were in the same range. However, reversible fouling was significantly lower after tank coagulation and flocculation, in spite of floc breakage in the membrane feed pump. Indications are thus that, either the properties of the broken flocs are significantly different from freshly created ones, or that flocs regrow in the membrane capillaries.
Additional findings of this study show that if the coagulation pre-treatment is optimised, MS2 bacteriophages can be efficiently removed from surface water characterized by high NOM content. Removal rates of 6 log units up to complete virus retention were achieved, at pH values ranging from 5.0 to 5.5. However, at such conditions the residual metal concentration exceeded legal limits. In order to avoid this, it is advised that the coagulation pH should be increased to 6 or higher. At these pH-values efficient virus removal can still be achieved, however, higher coagulant dosages are required. By optimizing coagulation/flocculation pre-treatment, an efficient removal of NOM can be achieved while complying with hygienic barrier requirements, resulting in virus removal of 4 log units and higher. Coagulation/flocculation pre-treatment coupled with ceramic MF filtration is thus a viable and flexible treatment scheme for the production of high quality potable water from surface waters having high NOM concentrations.PhD i vann- og miljøteknikkPhD in Hydraulic and Environmental Engineerin
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
NOM removal in drinking water treatment using dead-end ceramic microfiltration: Assessment of coagulation/flocculation pretreatment
Full text linkIn Nordic countries, surface water is a common source for potable water production. Such waters are often characterised by high Natural Organic Matter (NOM) content, resulting in high colour, very low turbidity, low alkalinity and low hardness due to natural conditions. Treatment of such waters basically comprises the removal of NOM and colour, corrosion control and disinfection. Although the largest part of NOM is not harmful, some fractions can cause colour, taste and odour problems or can even be toxic. Complexation of heavy metals and organic micro-pollutants, mobilizing them and making them available in the water phase, and increasing the amount of necessary disinfectants as well as being recognized as precursors for disinfection by-product formation which can be carcinogenic, are issues to be considered. In addition, there is a growing concern on the increase of NOM in natural water sources. Recent studies have shown that the concentration of NOM in surface water has increased in the last decades and may increase further during the coming decades, caused by progressing climate change issues and/or changed precipitation patterns. Thus, the removal of NOM is one of the major concerns and makes advanced drinking water treatment necessary.
In the past, conventional treatment processes such as coagulation/rapid sand filtration and filtration by nanofiltration (NF) membranes have been used successfully in Norway. However, a number of disadvantages have been identified in these processes. While the quality off effluent from rapid filters is high if coagulation is optimised, it may be severely compromised if coagulation fails, or operation is unstable. NF membranes have been subject to high irreversible fouling. High operating pressures at low fluxes, permeability loss over time and high chemical demands for cleaning have been observed frequently. By contrast, low pressure membrane filtration has emerged as an alternative for direct surface water treatment in recent years, with number of installations increasing rapidly around the world. Disadvantages as described above can be avoided to a large extent with this technology. The usage of low pressure membrane processes leads to high, stable effluent quality compared to conventional technologies, especially with regards to hygienic aspects since water borne parasites and most of bacteria can be retained. By applying ceramic microfiltration (MF) a more energy efficient operation is possible, the higher investment costs for ceramic membranes can be offset by the ability to operate with significantly higher fluxes. However, such membranes demand coagulation pre-treatment in order to achieve sufficient NOM and colour removal, fulfil the requirements as a hygienic barrier as well as for the control fouling by NOM.
This study showed that coagulation, combined with subsequent ceramic MF, is a successful concept for the direct treatment of Nordic waters. In spite of high NOM content in the raw water (DOC 6.8 mg C/L, colour 55 mg Pt/L), stable operation was demonstrated at high membrane fluxes of up to 250 L/(m2 h), achieving irreversible membrane fouling below 1 mbar/h, a DOC removal of 70% and colour removal of around 90%, at a coagulant dosage of 0.65 mg Al per mg DOC (using PACL at pH 6, with 60s of inline flocculation). While NOM removal depended only on coagulant dosage and coagulation pH, membrane fouling was also influenced by flocculation type, time and G-value. The study also found that the optimization of coagulation pretreatment is crucial. If, for example, an insufficient amount of coagulant is dosed, membrane fouling increases drastically, residual metal concentration is high and NOM removal is minimal. Inline coagulation with a static mixer, followed by pipe flocculation, showed promising results compared to conventional tank coagulation, where irreversible fouling rates observed were in the same range. However, reversible fouling was significantly lower after tank coagulation and flocculation, in spite of floc breakage in the membrane feed pump. Indications are thus that, either the properties of the broken flocs are significantly different from freshly created ones, or that flocs regrow in the membrane capillaries.
Additional findings of this study show that if the coagulation pre-treatment is optimised, MS2 bacteriophages can be efficiently removed from surface water characterized by high NOM content. Removal rates of 6 log units up to complete virus retention were achieved, at pH values ranging from 5.0 to 5.5. However, at such conditions the residual metal concentration exceeded legal limits. In order to avoid this, it is advised that the coagulation pH should be increased to 6 or higher. At these pH-values efficient virus removal can still be achieved, however, higher coagulant dosages are required. By optimizing coagulation/flocculation pre-treatment, an efficient removal of NOM can be achieved while complying with hygienic barrier requirements, resulting in virus removal of 4 log units and higher. Coagulation/flocculation pre-treatment coupled with ceramic MF filtration is thus a viable and flexible treatment scheme for the production of high quality potable water from surface waters having high NOM concentrations.PhD i vann- og miljøteknikkPhD in Hydraulic and Environmental Engineerin
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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