• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 2861
  • 2673
  • 487
  • 414
  • 335
  • 207
  • 78
  • 68
  • 65
  • 47
  • 47
  • 47
  • 47
  • 47
  • 47
  • Tagged with
  • 8510
  • 1836
  • 1647
  • 1361
  • 1351
  • 1137
  • 909
  • 885
  • 850
  • 645
  • 509
  • 474
  • 469
  • 460
  • 428
  • 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.
261

Regulating the environmental impacts of the electricity supply industry

Horne, Ralph January 2001 (has links)
The electricity supply industry (ESI) in England and Wales does not operate efficiently, in terms of optimising the balance between benefits of electricity and costs associated with environmental impacts. The optimal situation would be one where such impacts are minimised per unit of electricity service used, notwithstanding cost considerations. However, the present regulatory regime fails to account sufficiently for environmental impacts. Indeed, it cannot do so at present, due to lack of objective, complete and sufficiently accurate information. The main methods currently advocated for valuing environmental impacts are based on the theory of neo-classical environmental economics. These aim to place monetary values on impacts, which can then, in theory, be used to internalise environmental externalities, by applying market mechanisms to correct for the market inefficiency. However, numerous objections have been raised and weaknesses identified, including, principally, the lack of a systematic approach and the inability of the technique to accurately value impacts which are not usually considered in monetary terms. Better regulation starts with better understanding of the issue(s) to be regulated. In this case, it requires appropriate data about values of environmental impacts. While environmental economics is not rejected outright, further improvements are required and, in any event, it must be supplemented by a systematic approach, which encompasses a means of valuing non-economic elements of value. The Environmental Analysis, Valuation and Application (EAVA) Framework proposed here has been designed and developed in order to address these requirements. It also satisfies the need for objectivity, rigour, transparency, versatility, practicality and a step-by-step, sequential procedure for dealing appropriately with environmental impacts. The EAVA Framework encompasses four separate methods which have been developed simultaneously to work together in order to address different areas of the problem. The output analysis method allows the production of a complete inventory of released incidental outputs (RIOs) which arise from the process being studied. The pathway analysis method provides a means of tracing these RIOs through the environment and generating objective data about the resulting environmental changes. The valuation method is where the only necessary subjectivity of valuation is concentrated by accommodating the views of those whose quality of life is damaged by the impacts. The unit of valuation is the "natural" unit of quality of life outcome state (QLOS), and quantification is achieved through use of the QLOS Index. The final method is the application method, where valuation data and information about unknowns or other "gaps" in knowledge or data are utilised in mechanisms to ensure decision making and operation of the process concerned correctly reflects the environmental impacts caused. It should be noted here that procedures exist throughout the EAVA Framework for identifying and quantifying "gaps". The overall result is the EAVA Framework - a single integrated process for regulating environmental impacts, from the point of origin, to the point of applying regulation.
262

Temperature and physical modelling studies of open windrow composting

Irvine, Richard John January 2002 (has links)
There is a growing demand for sustainable forms of waste management due to both legislative pressures (e.g. the European Union Landfill Directive (99/31/EC)) and increasing public awareness of environmental issues. Composting of biodegradable waste materials to produce a stabilized beneficial multi-functional product (compost) is being widely promoted. Currently, the most popular method of composting is the open windrow method, whereby the mixed and shredded feedstocks are arranged in long rows termed windrows and turned on a regular basis. During the process the waste material is subject to aerobic exothermic microbial decomposition. Commercial composting operations suffer from the problem that much of the processing is performed using empirical approaches. Improved understanding of the composting process based on scientific methodology is required to allow composting to develop its potential as an economic, safe and reliable method of sustainable waste management. This study used a series of large scale windrow-based seasonal field trials employing urban green waste as a feedstock, to investigate in unprecedented detail the temperature trends and patterns of behaviour within such structures. In addition physical-chemical profiling was undertaken. It demonstrated that windrow temperature development is not uniform in either a spatial or temporal sense. Temperature variation is a key feature of composting. All regions of typical windrows exhibited thermophilic and mesophilic temperature zones throughout the composting process. There was little seasonal variation. Sustained high temperatures were most widespread in the core regions at a height of around lm. Thus, these areas should not be favoured during temperature assessment to avoid bias results. It was demonstrated that current methods of temperature assessment are inadequate. It is suggested that greater numbers of data points are collected at varying positions and instead of simply calculating overall mean temperature that individual trends are plotted. The use of temperature frequency distribution histograms and cumulative temperature plots is additionally advised. Increased windspeed (greater than approximately 15MPH) was demonstrated to be a major factor preventing the development and sustaining of thermophilic temperatures within windrows. It is recommended that commercial composters routinely assess windspeed and direction. Changes in organic matter content, bulk density and pH provided an indication of the composting process in the long term but lacked the sensitivity of temperature measurement. Surveying using electronic tacheometry allowed changes in windrow shape and volume to be assessed. The field trial data allowed a novel physical compost model to be developed, based upon open windrow composting of urban green waste. Existing models are based on in-vessel composting systems and are technically flawed in certain key aspects. The model successfully simulated the initial stages of windrow composting, which was proven by experimentation and comparison with field trial data. The use of low level internal feedstock heating was demonstrated to be a viable method of stimulating natural enhanced microbial activity. A non- insulated model windrow and the employment of an environmental simulation system allowed the natural relationship between windrow and external environment to be modelled. The importance of such a model to the compost scientist and waste manager is highlighted. The study showed that it is possible to successfully physically model the open windrow composting process.
263

Organophilic clays in stabilisation and solidification of hazardous wastes

Montgomery, Diana Margaret January 1989 (has links)
No description available.
264

Aspects of the anaerobic digestion of wattle tannins

Hurlow, Elton Lloyd January 1987 (has links)
The aqueous extract from the bark of the black wattle tree, (Acacia mearnsii De Wild)(1), is used extensively in the tanning industry for the production of sole and other heavy leathers as well as in lighter leathers and skins. The commercial extract is available in an easily dissolvable spray dried form and in deference to its genus name Mimosaceae is referred to in the trade as Mimosa(3). Mimosa extract consists primarily of high molecular weight polymeric flavonoid units which also constitutes the active tanning ingredient. Lower phenolics, gums and sugars or the so called "non-tannins" are present as impurities and contribute up to 40% to (3 ) the total mass of the extract.
265

A local authority waste management mass balance model

Greenfield, David W. J. January 2010 (has links)
The pressure at the turn of the 21st century for Waste Disposal Authorities to change their waste disposal systems was both urgent and comprehensive, with emphasis being placed on moving towards the 3Rs; Reducing, Recycling and Recovering value from Municipal Wastes. This thesis explores how a mass balance model was created for the Brighton & Hove City and East Sussex County council Private Finance Initiative (PFI) contract, in response to the pressures for change and need for investment up to 2002. An identification and evaluation of the drivers for change at the time has been undertaken; with it being demonstrated that legislation, lack of landfill space and underlying public pressure were the stimulus for change.
266

The plasma treatment of inorganic waste streams for the production of monolithic glass-ceramic tiles

Deegan, David January 2002 (has links)
No description available.
267

Waste policy formulation and implementation : recycling and landfill

Greaves, Christopher January 1994 (has links)
This thesis considers recycling as one option to improve the environmental performance of industry in the UK. A systems approach is used to identify objectives and capabilities of legislative and industrial agencies and to analyse issues in the broad context of waste policy formulation and implementation which spans both constituencies. It is shown that regulatory change to empower industrialists as decision takers is limited by a shortage of recycling infrastructure in the UK. Although well resourced firms are developing progressive waste policies in house, other firms are less well equipped to respond to regulatory pressures in a manner that is congruent with legislative objectives. An innovative option to develop recycling facilities for construction wastes at a landfill site is assessed, considering the roles of construction firms, skip hauliers and waste managers. An investigation is conducted into the practices employed by construction firms that influence wastes arising and likely changes to such practices. It is shown that pressures on construction firms are leading to some improvements to waste streaming that favour the recycling option. A spatial model of landfill catchment is used to estimate the elasticity of the volume of a given waste type delivered to a landfill site with respect to prices charged at the site and competing facilities. The option to recycle a substantial fraction of construction waste is compared with the null option of continuing to landfill waste without pre-treatment using a comparative cost benefit model. This model shows that, in the case of construction waste, benefits due to extending the working life of a landfill pit can be more significant than revenue effects for waste managers. Whether these benefits justify the costs of recycling is shown to be dependent on characteristics of particular landfill sites and
268

Estabilização de landfarming de refinaria de petróleo, mediante metabolismo microbiano, e aplicabilidade em solos pré-desertificados /

Hencklein, Fabiana Aparecida. January 2008 (has links)
Orientador: Dejanira de Franceschi de Angelis / Banca: Newton La Scala Júnior / Banca: Aurora Mariana Garcia de França Souza / Resumo: O aumento da população humana tem acrescentado ao meio ambiente grande quantidade e diversidade de compostos. Isto acopla-se ao desenvolvimento das atividades industriais acrescentando novas técnicas que geram novos resíduos. Essas substâncias podem ou não ser degradadas dentro dos processos edáficos. Os microrganismos têm sido por muito tempo os agentes controladores dos resíduos produzidos em nosso planeta, porém, os seres humanos ultrapassaram a capacidade de suporte do ecossistema. Sendo assim, a microbiota necessita de auxílio na biodegradação dos xenobióticos, estes têm sido adicionados aos solos. "Landfarming" consiste na aplicação do contaminante na camada arável do solo, onde esse resíduo é misturado mecanicamente por aração e gradeamento. Nestes sítios as condições físicoquímicas são ajustadas para maximizar a atividade microbiana. Este trabalho buscou verificar mediante estudos de respirometria, a biodegradação da matéria orgânica presente no solo de "landfarming" de refinaria de petróleo. Os resultados apontam que a evolução de CO2 ocorre neste solo e que sua eficiência de biodegradação aumenta (13,9%) quando se adiciona casca de grão de arroz em associação com vinhaça, resíduo proveniente das destilarias de etanol. Também detectou-se que a mistura de solo de cerrado, contendo baixa quantidade de matéria orgânica, pode estimular o aumento na liberação de CO2 (15,8%). Contudo, quando a essa mistura acrescenta-se casca de grão de arroz e vinhaça, o aumento da evolução de CO2 é mais pronunciado (78%). A atividade das bactérias e fungos também foi avaliada, mediante contagem das UFC/g/ss, e observou-se aumento de até 300 vezes no número de colônias nos tratamentos em que foram adicionados casca de arroz e vinhaça. / Abstract: The increase of human population added great amount and diversity of composts into the environment. This occurs because of the industrial activities development that adds new technologies, generating new wastes. These substances can or not be degraded by soil processes. The microorganisms have been for much time the controlling agents of residues produced in our planet. However, the human being had exceeded the ecosystem support capacity. So, microbial community needs help in biodegradation of xenobiotics added to soil. "Landfarming" consists in contaminants application at the arable layer of soil, where these wastes are mechanically mixed by tillage and the physico-chemical conditions are adjusted to maximize the microbial activity. This work verified, using respirometric methods, the biodegradation of organic matter present in "landfarming" soil of an oil refinery. The results showed that CO2 evolution occurs in this soil, and that its biodegradation efficiency increases (13,9%) when added rice grain husk in association with vinasse, an alcohol prodution waste. We also detected that the mixture with brazilians savanna soil, that has low organic matter amount, can stimulate the increase in CO2 release. However, when vinasse and rice grain husk are added to this mixture, CO2 evolution rises up (78%). The activity of the bacteria and fungus was also evaluated by means of UFC/g/ss counting. An increase of 300 times of colonies number was observed at the treatments where rice husk and vinasse had been added. / Mestre
269

ESTUDO DE VIABILIDADE TÉCNICO-ECONÔMICA DE UMA USINA DE INCINERAÇÃO DE RESÍDUOS SÓLIDOS URBANOS NO ABCD / FEASIBILITY STUDY TECHNICAL-ECONOMIC AN INCINERATION PLANTS MUNICIPAL SOLID WASTE IN ABCD

Andre Xavier Lima 22 December 1994 (has links)
A incineração de resíduos sólidos urbanos tem sido cogitada como solução para problemas relacionados com a destinação final dos resíduos gerados em regiões metropolitanas. Este trabalho reve a situação dos resíduos sólidos na sub-região sudeste da Região Metropolitana de São Paulo e analisa a viabilidade de uma usina de incineração com geração de energia elétrica para tratamento dos resíduos sólidos coletados na região. E realizada uma revisão das tecnologias existentes e da emissão de poluentes atmosféricos, inclusive dioxinas e furanos , por incineradores de grande porte . Apesar de não ser atrativa financeiramente para as taxas de desconto usuais e as atuais taxas de tratamento e disposição final praticadas, a alternativa da incineração oferece diversas vantagens que devern ser analisadas em estudos comparativos aprofundados com as demais opções para a disposição de resíduos sólidos da Região Metropolitana de São Paulo. / MSW incineration has been considered a solution to the problems related to final disposal of waste generated in metropolitan regions. This work reviews the situation of MSW in the southeastern region of the Metropolitan Area of Sao Paulo and analyses the viability of an incineration plant with electric power generation for the treatement of MSW colected in that region. Existing technologies are reviewed alongside with the emission of atmospheric pollutants, including dioxins and furans, for large scale incineration plants. Besides not being financially attractive with market discont rates and present treatement and final deposition taxes collected, the alternative of MSW incineration presents several advantages that deserve being assessed in detail on a comparative basis with other options for disposal of MSW in the Metropolitan Region of Sao Paulo.
270

A study of the effect of substrate composition on the microbial ecology of activated sludge

Noble, Raymond A. January 1997 (has links)
Eighty percent of all biologically treated waste waters in Europe are oxidised by the activated sludge process. Bulking sludge caused by the proliferation of filamentous organisms is the primary cause of failure of this system. The effect of various substrates in both laboratory scale, fully mixed and sequencing batch (SBR) reactor configurations were used to assess their combined effect on activated sludge microbial ecology and hence sludge settlement. Five different substrate types were used ; synthetic sewage, a basic monosaccharide, disaccharides, polysaccharides and amino acids. In all cases using the fully mixed reactor, bulking occurred while, good settling sludge was produced in the sequencing batch reactor. The cause of this bulking was deemed to be due to the lack of so called "selector effect" within the fully mixed reactor characterised by :- i) high rates of substrate consumption ii) high oxygen (or generally: electron acceptor) up take rate iii) enhanced growth of zoogleal bacteria iv) increased metabolic diversity This laboratory work was compared and contrasted with a pure oxygen activated sludge (VITOX) system treating a high strength pea processing waste water. This fully mixed system had proved difficult to operate since its installation and in the first two years of this study suffered bulking caused by low dissolved oxygen levels. In the third year a combination of a hydraulic problem and subsequent lack of control led to filamentous bulking. This particular bulking incident was controlled by the addition of chlorine to the aeration tank which was selectively toxic to the filamentous organisms present. Due to the studies carried out at both laboratory and full scale an initial contact zone was installed within the main aeration tank prior to the 4th year of this study so as to create an area of high floc loading and high substrate uptake. This initial anoxic contact zone proved successful in preventing the development of a poorly settling sludge and is in line with common practice for the elimination of filamentous bulking reported in the literature. Oxidation Reduction Potential (ORP) proved a reliable and appropriate monitor of conditions of low to zero D.O. experienced in the laboratory scale reactors and at full scale in the anoxic contact zone. It was also found that ORP could be used to detect when D.O. levels became completely depleted and monitor reductions in nitrate levels.

Page generated in 0.0289 seconds