• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 55
  • 41
  • 4
  • 2
  • 1
  • Tagged with
  • 150
  • 36
  • 28
  • 23
  • 22
  • 20
  • 19
  • 19
  • 18
  • 17
  • 17
  • 16
  • 16
  • 13
  • 13
  • 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.
21

Sustainable Management of Biogeochemical Cycles in Soils Amended with Bio-Resources from Livestock, Bioenergy, and Urban Systems

Schnell, Ronnie Wayne 2010 August 1900 (has links)
Bioresources are generated in a variety of environments and each presents unique risks and benefits associated with land application. Bioresources from livestock, urban and bioenergy systems were selected and evaluated through field, greenhouse and laboratory studies of potential risk and benefits of recycling to agricultural and urban landscapes. The waste stream, including feedstock sources and treatment processes, affects composition and properties of bioresources and effects on biogeochemical cycles of amended soils. Variation of decomposition and nutrient mineralization rates among bioresources used to amend soil for turfgrass and forage reflected variation among contrasting feedstock sources and treatments prior to application. During turfgrass establishment, plant available nitrogen and nitrogen mineralized from a bioresource from livestock waste streams, (Geotube! residual solids, supplied N in excess of crop uptake potential and contributed to leaching loss of N. In contrast, N mineralization rates from bioresources generated during methane production from dairy manure (manure solids) were not sufficient to maximize crop production, necessitating N fertilizer application. In addition to variation of composition, bioresource effects on crop productivity and environmental quality vary among management practices and between forage and turfgrass cropping systems. Large application rates of bioresources increase soil nutrient concentration and potential crop productivity, but contribute to increased nutrient loss in drainage and surface runoff. Yet, incorporation or Alum treatment of bioresources will reduce runoff loss of dissolved P and protect water quality without sacrificing crop productivity. Alum treatment of bioresources prior to land application effectively reduced runoff loss of dissolved P to levels observed for control soil. For situations in which large, volume-based bioresource rates are top-dressed or incorporated, export of applied nutrients environmental impacts were compared between forage and turfgrass systems. Starting during the initial year of production, annual export of applied N and P in Tifway bermudagrass sod was greater than export through forage harvests of Tifton 85. Low forage yield limited N and P export from Tifton 85 during the year of establishment, but increased forage yield during the second year increased export of manure N and P to levels more comparable to sod. As variation between compost sources, turfgrass and forage production systems, and application methods indicated, effective management of bioresources is necessary to balance benefits and risk in cropping systems. Integrated assessment of bioresource composition and crop-specific management of application method and rate will enable sustainable bioresource cycling and crop productivity.
22

Developing a process map for planning, initiating and operating municipal biosolids composting utilization programs in Southern Manitoba

Anseeuw, Carmen 07 February 2014 (has links)
The study objectives were to identify the best practice components of a biosolids composting utilization program; to determine current and emerging provincial and federal regulatory frameworks applicable to biosolids composting facilities in Manitoba; and to produce an annotated process map for planning, initiating and operating a biosolids composting facility. Recommendations from this study are to develop a stand-alone regulation that addresses composting requirements for probable feedstocks in provincial legislation, to clearly set out the requirements for such facilities; to update the Environmental Regulation for Treatment and Disposal of Biosolids in Manitoba policy document to acknowledge and provide guidance for biosolids composting as a potential management method; and to update and finalize the Manitoba Draft Compost Facility Guidelines to reflect current requirements for compost facilities and to include biosolids as a potential feedstock. The adoption of a categorization scheme for biosolids is also recommended to support determining appropriate management options based on biosolids quality.
23

Biomass, nutrient and trace element dynamics in cattail and switchgrass during wetland and terrestrial phytoremediation of municipal biosolids

Jeke, Nicholson 08 January 2015 (has links)
Knowledge of nutrient accumulation and partitioning in plants is important to determine the optimum timing of harvesting during phytoremediation of biosolids. This research showed that a greater proportion of nitrogen (N) and phosphorus (P) absorbed by cattail and switchgrass was partitioned to the aboveground biomass (AGB), but this partition decreased after the onset of nutrient retranslocation to roots. Therefore, AGB should be harvested prior to retranslocation in order to optimize nutrient phytoextraction. Trace elements partitioned preferentially to the root biomass, indicating that AGB harvesting will have little impact on their phytoextraction. Net mineralized N concentration (Nmin) in biosolids from the primary lagoon cell was optimized near field capacity [60% water filled pore space (WFPS) but changed little under drier conditions (30% WFPS). Under near-saturation conditions (90% WFPS), net Nmin decreased with incubation time, likely due to reduced mineralization and denitrification. Available (Olsen) P concentration was not affected by moisture content.
24

Developing a process map for planning, initiating and operating municipal biosolids composting utilization programs in Southern Manitoba

Anseeuw, Carmen 07 February 2014 (has links)
The study objectives were to identify the best practice components of a biosolids composting utilization program; to determine current and emerging provincial and federal regulatory frameworks applicable to biosolids composting facilities in Manitoba; and to produce an annotated process map for planning, initiating and operating a biosolids composting facility. Recommendations from this study are to develop a stand-alone regulation that addresses composting requirements for probable feedstocks in provincial legislation, to clearly set out the requirements for such facilities; to update the Environmental Regulation for Treatment and Disposal of Biosolids in Manitoba policy document to acknowledge and provide guidance for biosolids composting as a potential management method; and to update and finalize the Manitoba Draft Compost Facility Guidelines to reflect current requirements for compost facilities and to include biosolids as a potential feedstock. The adoption of a categorization scheme for biosolids is also recommended to support determining appropriate management options based on biosolids quality.
25

Inativação térmica de ovos de helmintos em água e em biossólidos digeridos: cinética em reator batelada e modelagem matemática em reator tubular. / Kinetics of helminth eggs inactivation in water and digested sludges by saturated steam produced with methane from anaerobic digestors.

Marilza de Fátima Simoneti 21 November 2006 (has links)
O biossólido pode ser um valioso recurso ao ser utilizado em solos agrícolas; porém, um dos principais problemas de sua utilização é a presença de patógenos que podem disseminar doenças. Os principais patógenos presentes no biossólido são vírus, bactérias, protozoários e helmintos. Dentre os patógenos existentes no biossólido, os ovos de helmintos são os mais resistentes à inativação térmica e, para helmintos, os ovos de Ascaris são utilizados como indicador desses parasitas devido à comum ocorrência e resistência térmica. Dentre os processos efetivos existentes para inativar patógenos do biossólido - compostagem, secagem e tratamento térmico, digestão aeróbia termofílica, irradiação com raios beta e gama e pasteurização - este último, utilizando como fonte de calor o vapor saturado gerado a partir da queima do metano produzido em digestores anaeróbios de ETEs convencionais, é um processo de tecnologia simples, com baixo custo de implantação e operação e necessita de pequena área para implantação, sendo indicado para grandes metrópoles de países em desenvolvimento. A inativação térmica de helmintos do biossólido é o objetivo deste projeto de pesquisa. São estudadas as cinéticas de inativação térmica de ovos de Ascaris suum em água e em biossólido digerido, utilizando-se reator batelada aquecido diretamente com vapor saturado. Aplicando-se o método integral, foram determinadas a ordem das reações, as constantes específicas de morte térmica e as energias de ativação. Os ovos de Ascaris suum utilizados no trabalho foram obtidos do útero de fêmeas adultas, e o método de Yanko foi empregado para recuperação dos ovos do biossólido digerido. A inativação térmica de ovos de Ascaris em água e em biossólido digerido em processo contínuo também foi estudada por meio da modelagem matemática de um reator tubular. Os modelos propostos foram o reator tubular isotérmico com perfil de escoamento não ideal e o reator tubular com perfil axial de temperatura e escoamento tubular ideal. O primeiro foi o que melhor ajustou-se aos dados experimentais. / Biological sludge can be a valuable resource for agricultural soil conditioning. However, an important obstacle for its use is the usual presence of pathogenic organisms, capable of disease dissemination. The main occurring pathogens are virus, bacteria, protozoa and helminth. Helminth eggs are very resistant to thermal inactivation. The Ascaris lumbricoids sp. are by far the most conspicuous and resistant among helminths, reason why they have been chosen as indicator organisms for this research. The main available systems to inactivate sludge pathogens are composting, drying and thermal treatment, anaerobic thermofilic digestion, beta and gamma radiation, and pasteurization. Pasteurization through application of saturated steam, produced from burning of methane gas, generated in anaerobic digestors is a very simple technology involving low capital costs and needing relatively small areas for implementation. It can be a valuable technology to attend conditions prevailing in large metropolitan areas of industrializing countries. Thermal inactivation of helminth eggs in water and sludge is the main purpose of this investigation. Kinetics studies of thermal inactivation by saturated steam was performed using batch reactors. Application of the integral method has allowed for the determination of reaction orders, the specific constants of thermal die away as well as the activation energies. The helminth eggs (Ascaris suum) utilized have been obtained from uterus of adult females and the Yanko method was utilized for the recovery of eggs from the digested sludge. In the same way the thermal inactivation of Ascaris eggs in water and in digested sludge has been performed in continuous process by mathematical modeling of a plug flow reactor. The proposed models were the isothermic plug flow reactor with a non-ideal flow profile and with an axial temperature profile and ideal flow. The experimental data has shown a better adjustment to the isothermic plug flow reactor.
26

Dimensions of Phosphorus Sustainability: Phosphorus Flows in a Rapidly Growing City and Field Tests of Potential Agricultural Prototypes

January 2020 (has links)
abstract: Phosphorus (P) is a limiting nutrient in ecosystems and is mainly used as fertilizer to grow food. The demand for P is increasing due to the need for increased food supply to support a growing population. However, P is obtained from phosphate rock, a finite resource that takes millions of years to form. These phosphate rock deposits are found in only a few countries. This uneven distribution of phosphate rock leads to a potential imbalance in socio-economic systems, generating food security pressure due to unaffordability of P fertilizer. Thus, the first P-sustainability concern is a stable supply of affordable P fertilizer for agriculture. In addition, improper management of P from field to fork leaves an open end in the global P cycle that results in widespread water pollution. This eutrophication leads to toxic algal blooms and hypoxic “dead zones”. Thus, the second P-sustainability concern involves P pollution from agriculture and cities. This thesis focuses on P flows in a city (Macau as a case study) and on potential strategies for improvements of sustainable P management in city and agriculture. Chapter 2 showed a P-substance-flow analysis for Macau from 1998-2016. Macau is a city with a unique economy build on tourism. The major P flows into Macau were from food, detergent, and sand (for land reclamation). P recovery from wastewater treatment could enhance Macau’s overall P sustainability if the recovered P could be directed towards replacing mined P used to produce food. Chapters 3 and 4 tested a combination of P sustainability management tactics including recycling P from cities and enhancing P-use efficiency (PUE) in agriculture. Algae and biosolids were used as recycled-P fertilizers, and genetically transformed lettuce was used as the a PUE-enhanced crop. This P sustainable system was compared to the conventional agricultural system using commercial fertilizer and the wild type lettuce. Chapters 3 and 4 showed that trying to combine a PUE-enhancement strategy with P recycling did not work well, although organic fertilizers like algae and biosolids may be more beneficial as part of longer-term agricultural practices. This would be a good area for future research. / Dissertation/Thesis / Doctoral Dissertation Biology 2020
27

Stability of biosolids derived carbon in soils; evidence from a long-term experiment and meta-analysis

Snyder, Alice J. January 2020 (has links)
No description available.
28

Dewatering Of Biosolids By Sodium Ferrate

Rios, Andrea 01 January 2004 (has links)
This study was conducted to evaluate the effectiveness of the liquid form of ferrate for dewatering of biosolids from wastewater treatment facilities. Two different ferrate products prepared using calcium hypochlorite and sodium hypochlorite were used. Samples of anaerobic digested sludge and waste activated sludge with solids content of 2.1% and 0.95 %, respectively were conditioned with both products to evaluate and compare their effectiveness. Centrifugation and filtration of the sludge after conditioning were used. For centrifugation the volume reduction and the turbidity of the supernatant after centrifugation were evaluated. For filtration, the Capillary Suction Time test was used. The optimum doses and conditions for dewatering of the sludge using ferrate were determined for each type of sludge. The centrifugation and filtration results were compared with those obtained for polymer doses currently used at the wastewater treatment plants where the samples were collected and with ferric coagulants as well. The results of this research indicated that optimum pH was 7.0. The time required to achieve mechanical equilibrium defined as the time at which the volume occupied by the solids was no more than one percent of the preceding reading was 1800 seconds for both types of sludge. The optimum rotational speeds were 800 and 2400 for waste activated sludge and anaerobic digested sludge, respectively. The optimum ferrate dose for anaerobic digested sludge for centrifugation and filtration was 5000 mg/l. For waste activated sludge a dose of 10 mg/l was found to be effective for filtration and centrifugation. The results indicated that the ferrate product prepared using calcium hypochlorite provides better results for the waste activated sludge than the ferrate prepared using sodium hypochlorite, while for anaerobic digested sludge no significant difference was observed. Finally, the results show that ferrate is a cost-effective alternative for the conditioning and disinfection of waste activated sludge, but not for the conditioning of anaerobic digested sludge.
29

Availability and Surface Runoff of Phosphorus from Compost Amended Mid-Atlantic Soils

Spargo, John Thomas 07 January 2005 (has links)
The accumulation of P in soil from land-applied biosolids and manure increases the risk for P enrichment of agricultural runoff. Transport of these residuals to areas where P may be efficiently utilized is necessary to reduce the threat to water quality. Composting can improve biosolids and manure handling characteristics to make their transportation more feasible; however, little is known about P dynamics in compost-amended soil. We investigated the factors controlling P solubility and plant availability in two soils, a Kempsville fine sandy loam (Typic Hapludult) and a Fauquier silty clay loam (Ultic Hapludalf), amended with one of 4 composts (2 biosolids composts and 2 poultry litter - yard waste composts), poultry litter, or inorganic P (as KH2PO4) in incubation and greenhouse pot studies. We also compared the effects of compost, poultry litter and commercial fertilizer on surface P runoff from a Fauquier silty clay loam that had received compost, poultry litter, or commercial fertilizer for 5 years. Organic amendments with higher concentrations of Fe, Al, and Ca had lower relative P solubility/availability. Phosphorus solubility in the Kempsville fine sandy loam, having far lower native P binding capacity, was more affected by Fe, Al, and Ca applied with the organic amendments. The concentration of P in runoff from the compost treatments was higher; however, infiltration was increased and runoff decreased so the mass loss of P and sediment was lower. Improved soil physical properties associated with compost applications aid to limit P runoff. / Master of Science
30

A Comparative Study of Anaerobic Digestion Processes for Sewage Sludge

Webb, Jared A. 24 February 2006 (has links)
The Blue Plains Wastewater Treatment Plant in Washington, D.C. is in the process of updating its anaerobic digesters, with a completion date set for 2008. This research was undertaken to aid designers at Blue Plains by evaluating alternative digestion approaches. The technologies applicable to the plant included thermophilic anaerobic digestion, acid/gas phased digestion, and temperature phased anaerobic digestion. To obtain design data, a year long study was conducted using bench scale digestion systems operating at different solids retention times (SRT) and organic loading rates (OLR). The digesters were fed with mixed primary and secondary waste (50/50 by weight) from the Blue Plains wastewater treatment facility. The digesters were operated until they reached steady state as observed by volatile solids reduction (VSR), methane production, and volatile fatty acid (VFA) levels. At this point, samples of digested waste sludge were analyzed for residual biological activity, dewatering properties and headspace organo-sulfur production. Results from the study demonstrated that the TPAD digestion process had the lowest residual biological activity (RBA) after digestion, and that the single stage thermophilic digesters had the highest RBA. Sludge from single stage mesophilic digestion had the highest odor potential, with headspace gas tests generating over 1400 mg organo-sulfur per m3 of headspace gas, while both single stage thermophilic and TPAD systems generated less than 400 mg/m3 at all SRTs studied. / Master of Science

Page generated in 0.0371 seconds