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Fate of perfluoroalkyl acids in the aquatic environment with a focus on mass balance studiesFilipovic, Marko January 2015 (has links)
Perfluoroalkyl substances (PFASs) are man-made chemicals. Their unique properties make them beneficial for a wide range of industrial and consumer product applications, such as in aqueous film forming foam (AFFF), durable water repellent clothing, hydraulic oils and food packaging materials. Perfluoroalkyl acids (PFAAs), a class of PFASs, are highly persistent in the environment, and long chain PFAAs are bioaccumulative and toxic. International regulation and voluntary actions by the industry have been implemented and led to a recent reduction of primary emissions of PFAAs to the environment. However, point sources such as AFFF training sites as well as diffuse sources continue to contaminate water bodies, soil and biota. Reducing environmental pollution with PFAAs has therefore become a regulatory priority. Designing successful measures to reduce the PFAA contamination requires an understanding of the sources, transport and fate of PFAAs in the environment. Four scientific publications are included in this PhD thesis, which aimed at increasing the holistic understanding of the fate of PFAAs in aquatic systems. This was achieved by chemical trace analysis combined with mass balance modeling. The following topics were covered: Dispersion and fate of PFAAs from an AFFF-impacted site (Paper I), recirculation of PFAAs in the aquatic environment with focus on waste water treatment plants (WWTPs, Paper II), mass balance of PFAAs in the Baltic Sea (Paper III) and transport and fate of PFAAs in two pristine boreal stream catchments (Paper IV). Results from Paper I showed that AFFF-impacted sites at a former military airfield, which was abandoned for more than 30 years, continue to be point sources of PFAAs to recipients. The sum of PFAAs in the ground water and surface waters ranged from 740 to 51000 ng L-1 and <0.5 to 79 ng L-1, respectively. PFOS in muscle tissue of European perch from a nearby lake ranged from 77 to 370 ng g-1 wet weight, representing among the highest values reported worldwide for fish muscle. In Paper II the relative importance of environmental recirculation of PFAAs versus new releases from the technosphere was investigated for PFAAs in WWTP influents. It was shown that tap water can be an important source of PFAAs to WWTPs in areas with elevated environmental levels. This needs to be taken into account when calculating emissions via WWTP effluents. PFAA mass balances over the WWTPs suggested that PFHxA and PFOA were formed from precursor compounds within the plants. Assembled PFAA mass balances for the Baltic Sea (Paper III) showed that river inflow and atmospheric deposition were the dominant input pathways, while wastewater treatment plant (WWTP) effluents discharging directly into the Baltic Sea made a minor contribution. The inputs of PFAAs were estimated to be higher than the outputs, suggesting a current increase of the PFAA inventory in the Baltic Sea. Also the mass balance study of PFAAs in two remote stream catchments presented in Paper IV revealed that inputs dominated over outputs for both catchments, indicating that a considerable portion of the PFAAs deposited from the atmosphere is retained in soil or in deep ground water and may be released to surface and marine water environments in the future / Perfluoralkilne tvari (PFASs) su umjetne kemikalije. Zbog svojih jedinstvenih svojstava široko su primjenjive u industriji i izradi proizvoda krajnje potrošnje kao što su pjena za gašenje požara (AFFF), vodootporna odjeća, hidraulična ulja i pakiranja za hranu. Perfluoralkilna kiselina (PFAAs) iz skupine perfluoralkilnih tvari iznimno je dugotrajna u okolišu, a dugolančane PFAAs su bioakumulativne i otrovne. Poduzeta međunarodna regulativa i dobrovoljne akcije vodile su nedavno smanjenoj primarnoj emisiji PFAAs u okoliš. Unatoč tome, primarni izvori, kao što su mjesta na kojima se provode treninzi za gašenje požara i difuzni izvori i dalje zagađuju vode, tlo i biotu. Zbog toga, smanjenje onečišćenja okoliša izazvanog PFAAs predstavlja regulatorni prioritet. Stvaranje uspješnih mjera kojima bi se smanjilo onečišćenje izazvano PFAAs zahtjeva razumijevanje izvora, prijenosa i sudbine tih tvari u okolišu. U ovaj doktorat uključena su četiri znanstvena članka kojima je cilj povećati sveukupno razumijevanje sudbine PFAAs u vodenim sustavima. To je postignuto kemijskom analizom elemenata u tragovima u kombinaciji s modeliranjem masene ravnoteže. Obrađene su sljedeće teme: Širenje i sudbina PFAAs na područjima zahvaćenim AFFF (Članak I), ponovna cirkulacija PFAAs u vodenom okolišu s naglaskom na postrojenja za pročišćavanje otpadnih voda (Članak II), masena ravnoteža PFAAs u Baltičkom moru (Članak III) te prijenos i sudbina PFAAs u dva udaljena sjeverna vodena toka (Članak IV). Rezultati iz Članka I pokazali su da su područja zahvaćena AFFF na bivšem vojnom aerodromu napuštenom prije 30 godina i dalje je glavni izvor PFAA zagadenja okolisa. Zbroj PFAAs u podzemnim i površinskim vodama kreće se u rasponu od 740 do 51000 ng L-1 i <0.5 do 79 ng L-1. PFOS u mišićnom tkivu grgeča iz obližnjeg jezera kreće se od 77 do 370 ng g-1 mokre težine, predstavljajući jednu od najviših vrijednosti u svijetu za riblje mišiće. Članak II istražuje relativnu važnost ponovne cirkulacije PFAAs imajući na umu novu emisiju PFAAs iz tehnosfere u postrojenjima za pročišćavanje otpadnih voda. Cirkulacija/kruženje u okolišu može se pojaviti kada PFAAs iz sustava pitke voda (rijeka, bunara i jezera) odlaze u otpadne vode. Prikazano je kako voda iz slavine može biti važan izvor PFAAs sustavima za pročišćavanje otpadnih voda u područjima s povišenim razinama zaštite okoliša. To se treba uzeti u obzir pri računanju emisije putem strojeva koji se koriste za pročišćenje otpadnih voda. Masena ravnoteža PFAA u postrojenjima za pročišćavanje otpadnih voda upućuje na to da su PFHxA i PFOA stvoreni kao prethodni spojevi unutar postrojenja. Prikupljene masene ravnoteže PFAA za Baltičko more (Članak III) pokazale su da su pritoke rijeka i atmosfersko taloženje dominantni ulazni putovi, dok postrojenja za pročišćenje otpadnih voda pridonose tek u manjoj mjeri. Ulaz PFAAs je procijenjen višim od izlaza, što objašnjava trenutno povećanje sadržaja PFAA u Baltičkom moru. Masena ravnoteža PFAAs u dva udaljena riječna toka predstavljena u Članku IV otkriva da ulaz dominira nad izlazom za oba riječna toka, što upućuje na značajan udio PFAAs koji je iz atmosfere zadržan u tlu ili podzemnim vodama te može biti ispušten u područja površinskih voda i mora. / Perfluorerade alkylsyror (PFAA) är kemikalier som är producerade av människan. Deras unika egenskaper gör att de kan användas i många olika industriella applikationer. PFAAs används i brandsläckningsskum, vattenavvisande kläder, hydrauliska oljor och matförpackningar. PFAAs har visat sig vara persistenta i miljön, och långkedjiga PFAA-homologer har visat sig vara bioackumulerbara samt ha en toxisk verkan. Reglering på internationell nivå tillsammans med initiativ från industrin har lett till minskning av direkta utsläpp. Punktkällor som brandövningsplatser samt andra diffusa källor fortsätter att förorena omgivande vattendrag, jordlager och fauna. Den utbredda föroreningen av PFAAs har därför blivit prioriterad för reglering. För att förstå utsläppen av PFAAs i miljön, hur de transporteras samt deras öde i miljön, är det viktigt att utföra studier som belyser dessa områden. Denna doktorsavhandling inkluderar fyra vetenskapliga publikationer. Syftet med de underliggande studierna var att öka den holistiska förståelsen av PFAAs rörelse i akvatiska system. Studierna gjordes genom att kombinera kemiska analysmetoder med modellering. Följande studier genomfördes; Transport och spridning av PFAAs från en brandövningsplats (Paper I), recyklering av PFAAs i den akvatiska miljön med fokus på vattenreningsverk (Paper II), massbalans av PFAAs i Östersjön (Paper III), transport och öde av PFAAs i två pristina vattendrag (Paper IV). Resultat från (Paper I) visade att brandövningsplatser vid en flygplats som inte har varit i bruk i mer än 30 år, fortfarande är punktkällor av PFAAs till omgivande vattendrag. Summan av PFAAs koncentrationer i grundvattnet och ytvattnet sträckte sig från 740 till 51000 ng L-1 och <0.5 till 79 ng L-1 i respektive vattendrag. Koncentrationen av PFOS i muskelvävnad från aborre i en av sjöarna var 77 till 370 ng g-1 våtvikt. Dessa värden representerar några av de högsta uppmätta koncentrationerna i världen. I Paper II testades betydelsen av PFAAs från recirkulering i miljön i jämförelse med nya utsläpp från teknosfären. Recirkulering av PFAAs i miljön kan förekomma då PFAAs i inkommande vatten till reningsverk kommer från dricksvatten. Denna studie visar att dricksvatten kan vara en påtaglig källa av PFAAs till vattenreningsverk i områden med förhöjda halter av PFAAs i miljön. Detta måste tas hänsyn till när man beräknar emissioner med utgående vatten från vattenreningsverk. Massbalanser av PFAAs i reningsverken visar att PFHxA och PFOA bildades av prekursorämnen i vattenreningsverken. I Paper III beräknades massbalanserna av PFAAs i Östersjön, beräkningarna visar att floder och atmosfärisk nedebörd var de viktigaste källorna medan utsläppen från vattenreningsverk var markant lägre. Importen av PFAAs estimerades vara högre än exporten, varför vi tror att PFAAs mängden I Östersjön kommer att öka över tid. Vidare gjordes en mass balans av PFAAs i två avlägsna avrinningsområden (Paper IV). Resultaten visar att importen av PFAAs dominerar över exporten från båda avrinningsområdena. Detta indikerar att en stor del av PFAAs som kommer ner via nederbörd kommer att ansamlas i jorden eller i grundvattnet. Dessa PFAAs kan vid senare tillfälle komma att släppas ut till floder som rinner ut i marina vatten. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 2: Manuscript.</p><p> </p>
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Idiopathic Normal Pressure Hydrocephalus : Cerebrospinal Fluid Tap Test and Magnetic Resonance Imaging as Preoperative Prognostic InvestigationsVirhammar, Johan January 2014 (has links)
Idiopathic normal pressure hydrocephalus (iNPH) is a condition with dilated cerebral ventricles but intracranial pressure within normal limits. The symptoms of gait impairment, cognitive decline and urinary incontinence develop gradually. Treatment with shunt insertion results in improvement in eight out of ten patients. The cerebrospinal fluid tap test (CSF TT) and preoperative magnetic resonance imaging (MRI) are methods used to select patients who may benefit from shunt surgery, but they are performed and interpreted differently in different centers throughout the world. The aim of this thesis was to evaluate the performance of the CSF TT and the underlying mechanisms of improvement in gait function after CSF removal, and to investigate the prognostic value of preoperative MRI scans. Improvement in gait and changes in cerebral blood flow (CBF) after a CSF TT were investigated in two prospective studies that included 39 and 20 patients, respectively. Gait assessment and perfusion MRI were done before and several times during the first 24 hours after a CSF TT. Perfusion was investigated with pseudo-continuous arterial spin labeling. At the group level, gait function was significantly improved at all investigation times, but only one-third of individual CSF TT responders were improved at all investigation times. In patients with increased CBF in lateral and frontal white matter after the CSF TT, gait function improved more than it did in patients with decreased CBF in these regions. However, in the whole sample, there was no significant increase in CBF after CSF removal. Preoperative MRI scans were retrospectively evaluated in 109 patients with iNPH who had undergone shunt surgery. The callosal angle was smaller in shunt responders compared with non-responders. The following findings showed the highest association with a positive outcome after shunting: a small callosal angle, wide temporal horns, and occurrence of disproportionally enlarged subarachnoid space hydrocephalus. In conclusion, CBF in white matter close to the lateral ventricles may play a role in the reversibility of symptoms after CSF removal in patients with iNPH. The CSF TT should be reevaluated if the patient does not initially improve, and preoperative MRI investigations can add prognostic information regarding the selection of shunt candidates.
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Banning Bottled Water in Concord, MA: How an Apolitical Commodity Became PoliticalBegg, Rachel 25 March 2014 (has links)
This thesis paper explores how various actors gathered around bottled water when a ban was put into place in Concord, Massachusetts. The objective has been to answer the following questions: How does an apolitical commodity become a political one? Specifically, how does bottled water move from being an apolitical commodity to become a highly political one? What does this mean for environmental politics? I situate my theoretical approach within Martha Kaplan’s research with fountains and coolers. I use Bruno Latour to show in which ways this ban became a matter of concern, as well as how the ban and the plastic bottle are actors. I conducted fieldwork in Concord and I interviewed participants. My findings reveal that the ban brought meanings to the surface and challenged them or supported them in various ways. The discussions turned from the impact of bottled water on our environment to the political impact of bottled water companies and large corporations on local Concord issues.
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A proteomic study of plant messenger RNA cleavage and polyadenylation specificity factors and the establishment of an in vitro cleavage assay systemZhao, Hongwei. January 2008 (has links)
Thesis (Ph. D.)--Miami University, Dept. of Botany, 2008. / Title from second page of PDF document. Includes bibliographical references.
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Environmental life cycle assessment of water use in South Africa the Rosslyn industrial area as a case study /Landu, Landu. January 2005 (has links)
Thesis (M. Applied Science)(Environmental Technology)--University of Pretoria, 2005. / Includes summary. Includes bibliographical references. Available on the Internet via the World Wide Web.
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Bezpečnostní analýza síťového provozu / Security inspection of network trafficKult, Viktor January 2017 (has links)
Thesis topic concerns the issue of information security in corporate environments. Literature search includes information obtained by studying articles and literature in the field of information security. Resources were selected with a focus on the security risks, security technologies and legislative regulation. Attention is focused on technology that supports monitoring of communication flows in the data network. Overview of traffic operating a data network provides important information for the prevention or investigation of security incidents. Monitoring also serves as a source of information for the planning of the network infrastructure. It can detect faults or insufficient transmission capacity. The practical part is dedicated to implementation of the monitoring system in the real corporate networks. Part of the experience is the analysis of the network structure and choice of appropriate tools for actual implementation. When selecting tools, you can use the scoring method of multicriterial analysis options. The integration of the monitoring system is also the configuration of active network elements. Subsequent analysis of network traffic provides information about the most active users, most used applications or on the sources and targets of data transmitted. It provides a source of valuable information that can be used in case of failure on the network or security incident. The conclusion is a summary of the results and workflow.
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Isolamento e caracterização de Acanthamoeba spp. em água de torneira no Estado do Rio Grande do Sul / Isolation and characterization of Acanthamoeba spp. In tap water in the state of Rio Grande do SulWinck, Mari Aline Todero January 2011 (has links)
Amebas de vida livre (AVL) do gênero Acanthamoeba estão amplamente distribuídas no ambiente e podem tornar-se amebas patogênicas ao homem. O objetivo deste trabalho foi isolar em de água de torneira amebas de vida livre do gênero Acanthamoeba, identificá-las e classificá-las. Um total de 132 amostras de água de torneira foi coletado de escolas estaduais e municipais entre os meses de março a novembro de 2009. As amostras passaram pelo processo de filtração e as membranas foram semeadas em ágar não-nutriente 1,5% coberto por uma suspensão de E. coli inativadas pelo calor. Todas as amostras positivas para AVL foram submetidas à clonagem celular e identificadas como pertencentes ao gênero Acanthamoeba, através da morfologia dos cistos e trofozoitos e pela PCR utilizando oligonucleotídeos gênero-específicos que amplificam a região ASA.S1 do gene 18S rDNA. Ensaios fisiológicos de termo e osmotolerância foram utilizados para avaliar a patogenicidade dos isolados. Vinte sete isolados foram positivos para AVL e 10 foram identificados como pertencentes ao gênero Acanthamoeba tanto pelas características morfológicas quanto pela análise molecular. Destes, nove isolados apresentaram características do grupo II e um do grupo III, segundo Pussard e Pons (1977). A análise do sequenciamento através da comparação das sequências dispostas no GenBank, demonstrou a distribuição no grupo genotípicos T2 (40%), T2/T6 (40%), T6 (10%) e T4 (10%). Nos ensaios de termotolerância e osmotolerância 50% dos isolados obtiveram um baixo potencial patogênico. Os resultados indicaram a presença do gênero Acanthamoeba em água tratada no estado do RS, revelando sua importância epidemiológica e a necessidade de mais estudos para determinar sua distribuição no ambiente e seu potencial patogênico. / Free-living amoebae (FLA) of Acanthamoeba genus are widely distributed in the environment and can become human pathogenic amoebae. The aim of this study was to isolate from tap water in free-living amoebae of Acanthamoeba, identify them and then classify them. A total of 132 samples of tap water was collected from state and municipal schools between march and november 2009. The samples passed through the filtration process and the membranes were seeded in non-nutrient 1.5% covered by a suspension of E. coli heatinactivated. All samples of AVL were cloned and identified as belonging to the genus Acanthamoeba by the morphology of cysts and trophozoites by PCR using primers and genus-specific primers that amplify the ASA.S1 region of 18S rDNA gene. Tests of physiological thermotolerance and osmotolerance were used to evaluate the pathogenicity of the isolates. Twenty seven isolates of AVL and 10 were identified as belonging to the genus Acanthamoeba through the morphological and molecular analysis. Nine of the isolates showed characteristics of group II and one isolate showed characteristics of group III, according Pussard and Pons (1977). The sequencing analysis by comparing the sequences submitted to GenBank, showed that genotype distribution in group T2 (40%), T2/T6 (40%), T6 (10%) and T4 (10%). In tests of thermotolerance and osmotolerance 50% of isolates had a low pathogenic potential. The results indicated the presence of Acanthamoeba in tap water in the RS, revealing its importance and the need for more epidemiological studies to determine their distribution in the environment and its pathogenic potential.
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Isolamento e caracterização de Acanthamoeba spp. em água de torneira no Estado do Rio Grande do Sul / Isolation and characterization of Acanthamoeba spp. In tap water in the state of Rio Grande do SulWinck, Mari Aline Todero January 2011 (has links)
Amebas de vida livre (AVL) do gênero Acanthamoeba estão amplamente distribuídas no ambiente e podem tornar-se amebas patogênicas ao homem. O objetivo deste trabalho foi isolar em de água de torneira amebas de vida livre do gênero Acanthamoeba, identificá-las e classificá-las. Um total de 132 amostras de água de torneira foi coletado de escolas estaduais e municipais entre os meses de março a novembro de 2009. As amostras passaram pelo processo de filtração e as membranas foram semeadas em ágar não-nutriente 1,5% coberto por uma suspensão de E. coli inativadas pelo calor. Todas as amostras positivas para AVL foram submetidas à clonagem celular e identificadas como pertencentes ao gênero Acanthamoeba, através da morfologia dos cistos e trofozoitos e pela PCR utilizando oligonucleotídeos gênero-específicos que amplificam a região ASA.S1 do gene 18S rDNA. Ensaios fisiológicos de termo e osmotolerância foram utilizados para avaliar a patogenicidade dos isolados. Vinte sete isolados foram positivos para AVL e 10 foram identificados como pertencentes ao gênero Acanthamoeba tanto pelas características morfológicas quanto pela análise molecular. Destes, nove isolados apresentaram características do grupo II e um do grupo III, segundo Pussard e Pons (1977). A análise do sequenciamento através da comparação das sequências dispostas no GenBank, demonstrou a distribuição no grupo genotípicos T2 (40%), T2/T6 (40%), T6 (10%) e T4 (10%). Nos ensaios de termotolerância e osmotolerância 50% dos isolados obtiveram um baixo potencial patogênico. Os resultados indicaram a presença do gênero Acanthamoeba em água tratada no estado do RS, revelando sua importância epidemiológica e a necessidade de mais estudos para determinar sua distribuição no ambiente e seu potencial patogênico. / Free-living amoebae (FLA) of Acanthamoeba genus are widely distributed in the environment and can become human pathogenic amoebae. The aim of this study was to isolate from tap water in free-living amoebae of Acanthamoeba, identify them and then classify them. A total of 132 samples of tap water was collected from state and municipal schools between march and november 2009. The samples passed through the filtration process and the membranes were seeded in non-nutrient 1.5% covered by a suspension of E. coli heatinactivated. All samples of AVL were cloned and identified as belonging to the genus Acanthamoeba by the morphology of cysts and trophozoites by PCR using primers and genus-specific primers that amplify the ASA.S1 region of 18S rDNA gene. Tests of physiological thermotolerance and osmotolerance were used to evaluate the pathogenicity of the isolates. Twenty seven isolates of AVL and 10 were identified as belonging to the genus Acanthamoeba through the morphological and molecular analysis. Nine of the isolates showed characteristics of group II and one isolate showed characteristics of group III, according Pussard and Pons (1977). The sequencing analysis by comparing the sequences submitted to GenBank, showed that genotype distribution in group T2 (40%), T2/T6 (40%), T6 (10%) and T4 (10%). In tests of thermotolerance and osmotolerance 50% of isolates had a low pathogenic potential. The results indicated the presence of Acanthamoeba in tap water in the RS, revealing its importance and the need for more epidemiological studies to determine their distribution in the environment and its pathogenic potential.
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Isolamento e caracterização de Acanthamoeba spp. em água de torneira no Estado do Rio Grande do Sul / Isolation and characterization of Acanthamoeba spp. In tap water in the state of Rio Grande do SulWinck, Mari Aline Todero January 2011 (has links)
Amebas de vida livre (AVL) do gênero Acanthamoeba estão amplamente distribuídas no ambiente e podem tornar-se amebas patogênicas ao homem. O objetivo deste trabalho foi isolar em de água de torneira amebas de vida livre do gênero Acanthamoeba, identificá-las e classificá-las. Um total de 132 amostras de água de torneira foi coletado de escolas estaduais e municipais entre os meses de março a novembro de 2009. As amostras passaram pelo processo de filtração e as membranas foram semeadas em ágar não-nutriente 1,5% coberto por uma suspensão de E. coli inativadas pelo calor. Todas as amostras positivas para AVL foram submetidas à clonagem celular e identificadas como pertencentes ao gênero Acanthamoeba, através da morfologia dos cistos e trofozoitos e pela PCR utilizando oligonucleotídeos gênero-específicos que amplificam a região ASA.S1 do gene 18S rDNA. Ensaios fisiológicos de termo e osmotolerância foram utilizados para avaliar a patogenicidade dos isolados. Vinte sete isolados foram positivos para AVL e 10 foram identificados como pertencentes ao gênero Acanthamoeba tanto pelas características morfológicas quanto pela análise molecular. Destes, nove isolados apresentaram características do grupo II e um do grupo III, segundo Pussard e Pons (1977). A análise do sequenciamento através da comparação das sequências dispostas no GenBank, demonstrou a distribuição no grupo genotípicos T2 (40%), T2/T6 (40%), T6 (10%) e T4 (10%). Nos ensaios de termotolerância e osmotolerância 50% dos isolados obtiveram um baixo potencial patogênico. Os resultados indicaram a presença do gênero Acanthamoeba em água tratada no estado do RS, revelando sua importância epidemiológica e a necessidade de mais estudos para determinar sua distribuição no ambiente e seu potencial patogênico. / Free-living amoebae (FLA) of Acanthamoeba genus are widely distributed in the environment and can become human pathogenic amoebae. The aim of this study was to isolate from tap water in free-living amoebae of Acanthamoeba, identify them and then classify them. A total of 132 samples of tap water was collected from state and municipal schools between march and november 2009. The samples passed through the filtration process and the membranes were seeded in non-nutrient 1.5% covered by a suspension of E. coli heatinactivated. All samples of AVL were cloned and identified as belonging to the genus Acanthamoeba by the morphology of cysts and trophozoites by PCR using primers and genus-specific primers that amplify the ASA.S1 region of 18S rDNA gene. Tests of physiological thermotolerance and osmotolerance were used to evaluate the pathogenicity of the isolates. Twenty seven isolates of AVL and 10 were identified as belonging to the genus Acanthamoeba through the morphological and molecular analysis. Nine of the isolates showed characteristics of group II and one isolate showed characteristics of group III, according Pussard and Pons (1977). The sequencing analysis by comparing the sequences submitted to GenBank, showed that genotype distribution in group T2 (40%), T2/T6 (40%), T6 (10%) and T4 (10%). In tests of thermotolerance and osmotolerance 50% of isolates had a low pathogenic potential. The results indicated the presence of Acanthamoeba in tap water in the RS, revealing its importance and the need for more epidemiological studies to determine their distribution in the environment and its pathogenic potential.
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Trihalomethane compounds in the drinking water of Kuwait : a survey from source to consumerLatif, Nidhal Abbas Abdul January 1991 (has links)
A comprehensive survey of the presence of trihalomethane (THM) compounds, as chlorination by-products, in drinking water in Kuwait have been performed. The survey covers the whole drinking water treatment cycle, starting with sea water and ending with the consumer tap. The data generated by the survey was all derived from actual water treatment plants, operating under normal conditions. All four trihalomethane compounds, namely; chloroform (CHCI3), bromodichloromethane (CHBrCI2), dibromochloromethane (CHBr2CI) and bromoform (CHBr3) were covered. The study clearly showed that, although considerable amounts of THM compounds did form as a result of chlorination of sea water entering the multi-stage flash (MSF) distillation plants, these plants were highly efficient in removing these compounds. The average removal efficiency, based on THM compounds mass load in the sea water feed, was around 95%. Factors which were found to have an influence on the degree of formation of these compounds, include, chlorination practice (continuous vs. shock), sea water temperature, level of organic precursors and contact time. Of much more important consequence, as far as the presence of these compounds in drinking water is concerned, was the degree of THM compounds formation as a result of the chlorination of drinking water before it is pumped to the consumer. Here, not only all the compounds formed remain in the water but there is a definite tendency for continuous formation well after the actual chlorination process has taken place. Factors which were found affecting this formation include water temperature, contact time and chlorination dosage. Although, all samples collected showed that the presence of THM compounds was always below the United States Environmental Protection Agency maximum contaminant level of 100 ~g/L, a need exists for the optimization of all chlorination processes with particular emphasis on the chlorination of drinking water. In almost all kinds of water encountered in this study, bromoform was found to be by far the most dominant compound.
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