• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 27
  • 3
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 46
  • 46
  • 46
  • 9
  • 7
  • 6
  • 6
  • 5
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • 3
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Využití potenciálu tvorby trihalomethanů k hodnocení účinnosti úpravy povrchové vody / Application of trihalomethane formation potential for evaluation of drinking water treatment efficiency

Halešová, Barbora January 2013 (has links)
The main theme of this thesis is the usage of the test investigating the formation potential of trihalogenmethanes (THM FP) and its comparison with conventional indicators of water quality (CODMn, A254 and colours). As for the experimental part of the thesis, rating of the effectiveness of selected technological procedures has been applied (e.g.: coagulation, adsorption and ozonation in the act of treatment of artificially prepared water model with a higher content of humic substances in laboratory conditions). Based on the obtained results, it was found that the common indicators of water quality have very similar attributes and also complete each other. On the contrary, those attributes of indicators may not be sufficient in case of the evaluation of water quality with high content of humic substances. The findings made illustrate that the THM FP test enables the accurate evaluation of water quality, especially in connection with the content of an organic material susceptible to chemical changes. THM formation potential has proved its high value and also has confirmed that it can appropriately complete the other standarts that are being used for assessing the quality of treated water up to nowadays.
42

Fluorescence probes: towards automatic coagulant dosing

Lecellier, Daphné January 2018 (has links)
There is a current lack of accurate tools to determine the concentration of cyanobacteria in situ.  Besides, cyanobacterial blooms have to be carefully monitored in reservoirs as they are more frequent because of climate change and can lead to potential released of toxins, along with other components. This project investigates the possible use of fluorescent probes to measure the concentration of different types of organic matter released by the algae. Three different species of toxic cyanobacteria were chosen to carry out this research as they are representative of the local harmful blooms found across Australia. Furthermore, the efficiency of two different chemicals (powdered activated carbon, also known as PAC, and alum) used in drinking water treatment plants were investigated, in order to determine a method for automatic dosage adjustment in water treatment plant. The organic matter was characterized by LC-OCD and fluorescence spectroscopy and statistical analysis such as principal component analysis was performed on the generated data. General characterization of the different species was firstly performed and globally, similar comportments were observed among the three cyanobacteria species. There is indeed a general increase in the release of organic material throughout the cell’s growth phase. Results from the jar tests showed that PAC mainly targeted humic-like substances and building blocks, which are middle size particles. The average removal rate obtained was 40µg/L per mg/L of PAC added into the water. Therefore, there is indication that the decreased efficiency for the removal of the taste and odor compounds observed in certain plants can be partially attributed to direct competition of organic matter adsorption onto PAC instead of a blockage of the PAC pores by larger particles. On the other hand, alum was able to remove large particles, particularly biopolymers and also humic-substances. However, a great increase of the low molecular weight molecules at very high doses of alum was seen, which suggest that a too high dose of alum is toxic for the algae cells. Based on the bench scale testing the recommended dose of 50 mg/L seems to be optimum for the studied water treatment plant. Specific ultraviolet absorbance and dissolved organic carbon measurements were also investigated and good correlations were found between the concentration of humic-like substances and absorbance, confirming that they are good measure to assess the content of organic matter in the water. However, as the slope coefficient of the linear trend varied between the species, it was not possible to obtain a common conversion factor for all the species. Finally, one fluorophore was found in common to all the samples and is characterized by the excitation-emission wavelength: 240/440 nm. Correlations with the chromatography’s results were investigated and this component seems to match the biopolymers and humic-like substances concentrations. Furthermore, its intensity decreases continuously with the addition of PAC whereas a drop was observed at the lower doses of alum. In regards on these findings, a method for automatic chemicals dosing from the fluorescence measures was proposed. / Detta examensarbete handlar om hur dricksvattenkvalitet kan kontrolleras och övervakas i vattenreningsverk. Nu existerar  inte någon exakt metod för att bestämma koncentrationen av cyanobakterier i vatten då det finns många olika arter. Men det är viktigt att övervaka algers tillväxt in i vattenreningsverk för de kan släppa ut skadliga ämnen till dricksvattnet. De tre arter som studerats i detta projekt är giftiga. Det organiska materialet i råvattnet kan också blockera membranporer eller leda till n biprodukter, som är cancerframkallande. Till sist konkurrerar några organiska substansen med smak- och luktföreningar för adsorptionsställena hos det pulverformiga aktiverade kolet. Därför är smaken och luktföreningarna inte väl borttagna, vilket leder till kundernas klagomål. Cyanobakterier måste övervakas noggrant.                            För att bestämma biologisk och kemisk egenskap hos vatten används flera tekniker för närvarande. I examensarbetet har undersökningar med vätskekromatografi och fluorescensteknik företagits. Kromatografi användes för att klassificera den organiska substansen i mindre grupper: biopolymerer, humus substanser, byggstenar och neutralmolekyler med låg molekylvikt (LMVN). Statistisk analys med R, inklusive huvudkomponentanalys företogs på insamlade data. Fluorescensdata registrerades också och visas i en excitationsutsläppsmatris.                            Experimenten reproducerade en behandlingsprocess och undersökte effektiviteten hos två kemikalier: pulveriserat aktivt kol (PAK) och alun. Resultaten visade att humusämnen   och dess byggstenar var väl borttagna av PAK medan även biopolymerer och humusämnen var väl bortagna av alun. Emellertid var en för hög dos av alun skadlig eftersom det ledde till en ökad frisättning av LMVN. I synnerhert kunde PAK ta bort 40µg/L av både humusämnen och dess byggstenar per mg/L av PAK tillagd. Det föreslår att de är de viktigaste konkurrenterna och att endast direkt konkurrens för adsorptionsställena sker. Om det fanns blockeringsfenomen, skulle det också finnas en minskning för biopolymererna. Den optimala doseringen av alun som bestämdes för det undersökta vattenreningsverket var 50 mg/L. Det kunde ta bort 60-70% av biopolymerer och 40-50% av humusämnen.                            Specifik ultraviolett absorbans och fluorescens registrerades. Båda visade riktigt bra korrelationer med humusämnen, vilket gör de till bra verktyg för att bedöma vattenkvaliteten. Men det kräver fortfarande att arten av cyanobakterie urskiljs eftersom koefficientens lutningar var olika. De kan därför vara ett verktyg för att mäta koncentrationen av organisk material, men arten måste vara känd. Fluorescencedata visade en topp vid 440 nm. En parallellfaktoranalys utfördes på data och endast en komponent hittades gemensam i alla prover. Därför studerades den maximala fluorescensintensiteten hos denna komponent. Å ena sidan kunde vi observera en kontinuerlig minskning av intensiteten när PAK tillsattes. Det är därför möjligt att veta hur man justerar den kemiska doseringen från fluorescensintensiteterna. I slutet av examensarbetet föreslås en metod för automatisk kemisk dosering. Fluorescensprober kan ännu inte exakt indikera cellkoncentrationen. Men med flera sonder som riktar sig till olika våglängder kan de redan vara till stor hjälp för styrning vid vattenverk.
43

Investigation of drinking water quality, sanitation-hygiene practices and the potential of indigenous plant seed for water purification in Southeast Ethiopia

Ahmed Yasin Mohammed 07 1900 (has links)
Background: Access to safe water and sanitation are universal need and basic human right, but the provision of quality water and improved sanitation remains a challenge in many African countries including Ethiopia. Objectives: The study investigated drinking water quality, sanitation-hygiene practices and the potential of Moringa stenopetala seed powder for the purification of water in Bale Zone, Southeast Ethiopia. Methodology: A community-based cross-sectional study was conducted among 422 randomly selected households in Robe and Ginnir Towns. Data were collected by interviewer-administered structured questionnaires from June 2012 to August 2013. An observation checklist was used to observe the sanitary condition of water sources. A total of 71 water samples were collected using sterile glass bottles in accordance with the standard method of American Public Health Association APHA. The physicochemical and bacteriological water quality analyses were done in Addis Ababa Environmental protection and Oromia water and Energy laboratories. The efficiency of Moringa stenopetala seed powder for removal of turbidity, hardness, and nitrate was evaluated. Data were analyzed SPSS Version 21.0 for the window. Descriptive analysis was done for appropriate variables. Logistic regression was used to identify the factors associated with under-five diarrhea. The results were presented using adjusted odds ratio and P-value of < 0.05 was used to declare significance association. Results: From the total sample, 401 respondents participated making a response rate of 95%. More than one third (37.9%) of the respondents were found to use pipe water. Two hundred and eighty (69.8%) of households wash storage containers before refilling and 325 (81%) of households were using separate containers for water storage. Two hundred seventy (67.3%) of the households had pit latrine. Prevalence of childhood diarrhea was found to be 50.1%. From the logistic regression model, those households having access to clean water source are 68% less likely to have under-five diarrhea, the households having clean storage of drinking water are 45% less likely to have under-five diarrhea in their home, and those households having poor latrine sanitation are 68% more likely to have under-five diarrhea in their home. Seed powder of 200mg/l Moringa stenopetala reduced the Nitrate concentration doses from 5.49mg/l to 8.18mg/l, a 75mg/l was reduced the turbidity from 4.49NTU to 1.07 NTU. A total hardness of 427 was reduced by 7.8% after treatment with powder seed of Moringa stenopetala. Conclusion: Prevalence of childhood diarrhea was high and it is associated with lack of access to a clean water source, poor sanitation of drinking water storage and latrine. Prevalence of open field defecation was remarkably high. The iron content of drinking water was above the range of World Health Organization standards. Moringa stenopetala seed powder has efficiency in the reduction of total and faecal coliform, turbidity, hardness and nitrate level in drinking water Recommendation: Health education on water handling, sanitation and low-cost effective water treatment methods like Using Moringa stenopetala seed should be practiced at the household level. / Environmental Sciences / Ph. D. (Environmental Science)
44

Strategic Assessment of Drinking Water Production Systems Environmental impacts from a Life cycle perspective : A case study of Norrvatten future drinking water production alternatives / Strategisk bedömning av dricksvattenproduktion. Miljöpåverkan ur ett livscykelperspektiv : En fallstudie av Norrvattens framtida alternative för dricksvattenproduktion

Aggarwal, Rahul January 2020 (has links)
Climate change is a global challenge that requires proactive action from municipalities, companies, and other organizations to prioritize sustainability in their daily operations. In the past few decades, life cycle assessment (LCA) approach has been successfully applied for environmental assessments in the drinking water sector. In this study, this approach has been used to present a comparative evaluation of the potential environmental impacts associated with nine different process alternatives for future drinking water production at Norrvatten. This study is a pioneering one that explores the potential of LCA as a decision support tool to prioritize and optimize environmental impacts during the operational phase in Swedish drinking water production. The nine alternatives are designed for the year 2050 to meet the average daily demand of 208 MLD for the 14 municipalities in the northern Stockholm region that Norrvatten supplies with drinking water. Out of the nine alternatives, the alternative based on direct filtration of raw water on nanofiltration membranes came out as the most environmentally friendly solution due to the use of renewable electricity from hydro and wind power. The results indicate that the potential environmental impacts are dominated by the use of chemicals in all alternatives, which in turn depends on the energy sources used for chemical production that are mostly dominated by fossil-based non-renewable sources. The impacts due to transportation and energy consumption are relatively less in Swedish drinking water production. Moreover, filtration through granulated activated carbon (GAC) is the most environmentally damaging treatment step, but regeneration of saturated GAC induces positive impacts in all alternatives. Among environmental impact categories, categories related to fine particulate matter formation; global warming, human carcinogenic toxicity, and human non-carcinogenic toxicity are the most significant in all alternatives. Several of the treatment technologies included in the nine alternatives, such as Nanofiltration, have only been tested on a pilot scale and have not been used for drinking water production at Norrvatten. So this study should be followed up and supplemented with better representative inventory data relevant to the Swedish context in order to contribute more effectively in making the future Swedish drinking water production more sustainable and environmentally friendly. Also, this study is based on the most recently available data that may not be valid in 2050 and the latest trends to substitute non-renewable energy sources with renewable sources may reduce the impacts due to chemical production and transportation in the future. Moreover, this LCA study does not include any aspects of water quality and treatment costs. Hence, while comparing different alternatives, the quality of the treated water and its production cost must also be taken into account. / Klimatförändringar är en global utmaning som kräver proaktivt agerande från kommuner, företag och andra organisationer för att prioritera hållbarhet i sin dagliga verksamhet. Under de senaste decennierna har livscykelanalys (LCA) använts för miljöbedömningar inom VA-sektorn. I denna studie har detta tillvägagångssätt använts för att presentera en jämförande utvärdering av den potentiella miljöpåverkan som är förknippad med den framtida dricksvattenproduktionen vid Norrvatten. Med hjälp av LCA så jämförs nio olika processalternativ för den framtida produktionen och kan på så sätt bidra till att prioritera och optimera processval utifrån miljösynpunkt. De nio alternativen är utformade för år 2050 för att tillgodose den genomsnittliga dagliga efterfrågan på 208 MLD för de 14 kommuner i norra Stockholmsregionen som Norrvatten försörjer med dricksvatten. Av nio alternativ kom alternativet baserat på direkt filtrering av råvatten på nanofiltreringsmembran som den mest miljövänliga lösningen på grund av användningen av förnybar el från vatten- och vindkraft. Resultaten indikerar att de potentiella miljöeffekterna domineras av användning av kemikalier i samtliga alternativ, vilket i i sin tur beror på de energikällor som används för kemikalieproduktion domineras av fossilbaserade energibärare. Effekterna på grund av transport och energiförbrukning är relativt låg i svensk dricksvattenproduktion. Filtrering genom granulerat aktivt kol (GAC) det mest miljöbelastande behandlingssteget, men regenerering av mättad GAC ger positiva effekter i alla alternativ. Bland kategorier för miljöpåverkan så är kategorier relaterade till bildning av fina partiklar; global uppvärmning, mänsklig cancerframkallande toxicitet och mänsklig icke-cancerogen toxicitet de viktigaste i alla alternativ. Flera av de behandlingstekniker som ingår i de nio alternativen, såsom Nanofiltration, har enbarts testats i pilotskala och inte använts för dricksvattenproduktion vid Norrvatten. Så denna studie bör följas upp och kompletteras med data som är relevanta för förhållanden vid Vättern Denna studie baseras också på tillgängliga data som kanske inte är giltiga 2050 och de senaste trenderna för att ersätta icke förnybara energikällor med förnybara källor som kan minska effekterna på grund av kemisk produktion och transport i framtiden. Dessutom innehåller denna LCA-studie inga aspekter av vattenkvalitet och behandlingskostnader.. Vid jämförelse av olika alternativ måste även kvaliteten på det behandlade vattnet och dess produktionskostnad beaktas.
45

Analysis of Oregon's Domestic Well Testing Act data for use in a sentinel surveillance system for private well contaminants

Hoppe, Brenda O. 01 May 2012 (has links)
The Safe Drinking Water Act ensures that public systems provide water that meets health standards. However, no such protection exists for millions of Americans who obtain water from private wells. Concern for safety is warranted as most wells draw from underground aquifers, and studies demonstrate that groundwater is affected by a range of contaminants, most often nitrate. Oregon's Domestic Well Testing Act (DWTA) links well testing to property sales, enabling continuous data collection by the State. This research addresses a need for identifying datasets for characterizing exposure to private well contaminants by evaluating DWTA data for use in a sentinel surveillance system. Validation of DWTA data was accomplished by developing a land use regression (LUR) model based on agricultural nitrogen inputs and soil leachability to predict nitrate concentrations in well water. Geographic information systems (GIS) were used to advance methods for high resolution spatial modeling of fertilizer and manure nitrogen with statewide coverage. Hazard mapping with these datasets suggests that nearly half of recently drilled wells are susceptible to nitrate contamination. Spearman's rank correlation demonstrated a significant correlation between LUR-predicted nitrate levels and levels reported in the DWTA dataset. These results suggest that DWTA data is valid for use in a sentinel surveillance system, such that evidence of nitrate contamination in a single well may indicate an area-wide health hazard. However, a low fraction of variance explained by the LUR model highlighted the need for specific improvements to datasets crucial for understanding nitrate contamination in well water, including the DWTA. / Graduation date: 2012
46

Factors associated with the problematical of quality drinking water and public health in the municipality of Abomey-calavi in Benin / Facteurs associés à la problématique de la qualité de l'eau de boisson et la santé des populations dans la commune d'Abomey-calavi au Benin

Degbey, Cyriaque 04 May 2011 (has links)
The objective of this research is double: <p>1) to study the factors associated with the problems of quality with drinking water on the physicochemical and biological level in the municipality of Abomey-Calavi in Benin ;<p>2)to study its relationships with public health. <p>The goal is to bring on one hand, the tools of improvement to the quality of water and public health in this commune. In addition, to contribute to the reduction of the rate of morbidity and mortality generated by the diseases related to drinking water contamination in this locality<p><p>Methods:<p>For the purpase of this study, we made a preliminary investigation in the municipality (households 55898 and almost all the households have the traditional wells). In the same way the information provided by the National Society of Water in Benin gave the indications on the level koverage of drinkable water conveyance of the commune. This study carried out within a general logical framework of the durable development based on an DPSIR analysis in the municipality of Abomey-Calavi of the Atlantic district in Benin made it possible to provide information on the main sources of contamination of the drinking water. We also carried out a random sampling of 110 wells and 110 households by taking account into the geographical distribution of the households in the commune. We selected 60 taps and 60 households by random sampling for those using water drink distributed by the national Society of Water in Benin. In each zone or district, three households consuming either well water or tap water were drawn randomly. A retrospective study on the number of cases of the hydrous diseases and other symptoms of hydrous diseases was carried out by consultation of medical registers of the commune from 2007 to 2009. Cases of diarrhoeas used as basic variable of health were compared with the other cases of hydrous diseases available in the files. <p><p>Results:<p>The results show that: the most al the well water taken in the households has temperatures beyond the recommendation of the World Health Organization (25 °C) and 98.2 % have a pH below the normal which is 6.5 to 8.5. We note a strong mercury and cadmium, complete iron, aluminum, nitrate nitrite pollution of the sampled wells (n=110) which is respectively 32.73%, 11.82%,10%, 43.64%, 6.36% and 14.55%. The results of the bacteriological analysis of water revealed that the totality of the wells is contaminated. The germs identified during the analysis of the well water are: Escherichia coli, fecal streptococcus species, bacterial salmonella ,Shigella ,Clostridium perfringens, staphylococcus species,<p> Klebsiella pneumoniae and Pseudomonas aeruginosa Most frequent among these germs are: Escherichia coli (100%), Klebsiella pneumoniae (97.27%), bacterial salmonella and Shigella (96,36%) with regard to the coliformes and enterobacteries. As for the cocci with Gram (+) they are staphylococcus species (97.27%) and the fecal streptococcus (88.18%). It is useful to stress that all the wells are strongly contaminated by Clostridium perfringens (95.45%).<p> The differences between the respective prevalence of parasitic coprology, uroculture, diarrhoeas, pains abdominal and saddles bloody for exposed (45.4%, 71.8%, 76.4% and 59.1%) :those who consume the water of wells not exposed (8.3%, 1.7%,13.3%, 16.7): those who consume tap water, are statistically significant (p<0.001). For diarrhoeas according to the characteristics of the people reached of hydrous diseases and other symptoms of hydrous diseases we have: <p>•\ / Doctorat en Sciences de la santé publique / info:eu-repo/semantics/nonPublished

Page generated in 0.0927 seconds