• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 111
  • 19
  • 5
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 1
  • Tagged with
  • 151
  • 151
  • 151
  • 51
  • 39
  • 25
  • 24
  • 24
  • 21
  • 18
  • 18
  • 17
  • 14
  • 13
  • 12
  • 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.
131

Bioaccumulation of Triclocarban, Triclosan, and Methyl-triclosan in a North Texas Wastewater Treatment Plant Receiving Stream and Effects of Triclosan on Algal Lipid Synthesis.

Coogan, Melinda Ann 08 1900 (has links)
Triclosan (TCS) and triclocarban (TCC), widely used antimicrobial agents found in numerous consumer products, are incompletely removed by wastewater treatment plant (WWTP) processing. Methyl-triclosan (M-TCS) is a more lipophilic metabolite of its parent compound, TCS. The focus of this study was to quantify bioaccumulation factors (BAFs) for TCS, M-TCS, and TCC in Pecan creek, the receiving stream for the City of Denton, Texas WWTP by using field samples mostly composed of the alga Cladophora sp. and the caged snail Helisoma trivolvis as test species. Additionally, TCS effects on E. coli and Arabidopsis have been shown to reduce fatty acid biosynthesis and total lipid content by inhibiting the trans-2 enoyl- ACP reductase. The lipid synthesis pathway effects of TCS on field samples of Cladophora spp. were also investigated in this study by using [2-14C]acetate radiolabeling procedures. Preliminary results indicate high TCS concentrations are toxic to lipid biosynthesis and reduce [2-14C]acetate incorporation into total lipids. These results have led to the concern that chronic exposure of algae in receiving streams to environmentally relevant TCS concentrations might affect their nutrient value. If consumer growth is limited, trophic cascade strength may be affected and serve to limit population growth and reproduction of herbivores in these riparian systems.
132

Assessment of the Efficiency of Wastewater Treatment Facilities and the Impact of their Effluents on Surface Water and Sediment in Vhembe District, South Africa

Edokpayi, Nosa Joshua 05 1900 (has links)
PhD (Environmental Sciences) / Department of Hydrology and Water Resources / See the attached abstract below
133

Exploring Spatial Optimization Techniques for the Placement of Flow Monitors Utilized in RDII Studies

Skehan, Christopher A. 31 August 2010 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / The aging infrastructure of a wastewater collection system can leak, capture ground water, and capture precipitation runoff. These are some of the most common problems in many of today’s US collection systems and are often collectively referred to as Rain Derived Inflow and Infiltration (RDII or I/I). The goal of this study is to investigate such optimized methods and their potential to improve flow monitor placement, especially for RDII studies, and to improve upon Stevens (2005) methodology. This project adopts a methodology from the “facility location problem”, a branch of operations research and graph theory. Solutions to a facility location problem will be adapted and utilized within a transportation GIS application to determine optimal placement.
134

Evaluating the impact of asset management in the water industry : a case study of East Rand Water Care Company (ERWAT)

Mhlongo, Thabani 04 1900 (has links)
Thesis (MPA)--Stellenbosch University, 2014. / The asset management process and strategy has been adopted and implemented within the public sector. Although the National Treasury developed the Capital Asset Management Guidelines to assist with the development and implementation of the asset management system the guidelines have received very little attention over the years. The Auditor General’s findings indicate a lack of proper implementation of the asset management process. The study provides a clear indication of the implementation of the asset management process by most government entities, local government municipalities and the public sector. The outcome is that while most entities have made progress with regards to the implementation, much remains to be done. Most entities implement the asset management process selectively. This does not yield positive and sustainable results and they end up abandoning the whole asset management system. The report provides the process of successful development and implementation of asset management, it also indicate that if there are element that are missed or not properly done the process will not yield constant results or performance and the impact on the organization performance will not be positive. The management of the organization must ensure that asset management is aligned with strategic objectives of the organization and performance measurement must be directly linked with asset management, performance measurement should be used to determine progress and implementation. Service level agreements must be established between all relevant departments including the finance department and there must be agreement on the objectives between all stakeholders. The key to proper implementation is the alignment of the asset management process with the strategic objectives of the organization.
135

Recovery of the Fish Population of a Municipal Wastewater Dominated, North Texas Creek After a Major Chlorine Disturbance

Maschmann, Gerald F. 08 1900 (has links)
This study evaluated the effects of a major chlorine disturbance on fish communities in Pecan creek by the City of Denton's Pecan Creek Water Reclamation Plant. Fish communities in Pecan Creek were sampled using a depletion methodology during February, April, July, and November, 1999. February and April sampling events showed that the fish communities were severely impacted by the chlorine. Sampling during July and November showed fish communities recovered in Pecan Creek. The first-twenty minutes of shocking and seining data were analyzed to mirror an equal effort methodology. This methodology was compared to the depletion methodology to see if the equal effort methodology could adequately monitor the recovery of Pecan Creek after the chlorine disturbance. It was determined that the equal effort methodology was capable of monitoring the recovery of Pecan Creek, but could not accurately represent the fisheries community as well as the depletion method. These data using the twenty-minute study were compared to a previous study. Results of this study were similar to those found in a previous study, although fish communities were more severely impacted and took longer to recover.
136

Macroinvertebrate Community Structure as an Indicator of Watershed Health in the Upper Trinity River Basin, North Central Texas

Stephenson, Jaynie M. 05 1900 (has links)
This study describes macroinvertebrate community structure and assesses its potential in detecting point and non-point sources of disturbance associated with rural and urban areas in the Upper Trinity River Basin. Geospatial techniques were used to quantify landuse within the watershed in a GIS. At rural sites near the headwaters of the Trinity River, collector-gathering burrowers that are adapted to minimal flow comprised the majority of taxa. Destinies of taxa compositions at downstream sites increased and shifted toward psammophilic and rheophilic invertebrates, including primarily collector-filtering clingers, that are characteristic of shifting sand habitats in large prairie rivers. Benthic community structure generally benefited from point source impacts including wastewater treatment plant effluents that maintained higher flow. Community indices were negatively associated with forest landuse and positively associated with urban landuse. Partial CCA determined that flow and landuse contributed equally to species dispersions. Comparisons with historical biomonitoring studies in upper Trinity River Basin indicate improved watershed health.
137

Synthesis and characterization of pine cone carbon supported iron oxide catalyst for dye and phenol degradation

Mmelesi, Olga Kelebogile 06 1900 (has links)
M. Tech. (Department of Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Technology / Fenton oxidation is classified into two processes, homogeneous and heterogeneous. Homogeneous Fenton oxidation process, have been shown to be efficient in the degradation of organic pollutants. However, it was shown to have limitations which can be addressed by the heterogeneous Fenton oxidation. Despite the high efficiency of the heterogeneous Fenton oxidation process in the degradation of recalcitrant organic pollutants, the currents synthesis trends of the heterogeneous Fenton catalyst have been proven to be time and energy constraining, since it involves the multi-step were the activated carbon have to be prepared first then co-precipitate the iron oxide on the activated carbon. However, as much as the heterogeneous Fenton catalyst has been proven to have high catalytic activity towards degradation of organic pollutants, these catalysts have some limitations, such limitations include metal ions being leached from the catalyst support into the treated water causing catalyst deactivation and a secondary pollution to the treated water. In this thesis, these catalysts have been applied in the degradation of recalcitrant organic pollutants such as methylene blue and phenols. This study focuses on the single step synthesis of iron oxide nanoparticles supported on activated carbon, were carbonaceous material is impregnated with iron salt then pyrolysed via microwave heating. Microwave power and the amount of iron salt were optimized. The prepared activated carbon-iron oxide composites were applied to the degradation of 2-nitrophenol (2-NP) and methylene blue (MB). Methylene blue was used as a model compound due to the fact that it is easier to monitor the degradation process with UV-Vis as compared to 2-nitrophenol . 2-nitrophenol the additional step for the adjustment of pH is required since nitrophenols are colorless in color at lower pH. The characterization showed that the microwave power and the amount of the iron precursor have an influence on the porosity and surface functional groups of the activated carbon. Further it was vi observed that microwave power and iron precursor influnces the amount of iron oxide formed on the surface of the support. It was also observed that the activated carbon-iron oxide composite have the catalytic effects on the Fenton oxidation process of MB and 2-NP. The parameters such as H2O2, pH, catalyst dose, initial concentration, temperature affect the degradation of both MB and 2-NP. Kinetics studies showed that Fenton is a surface driven reaction since the results fitted the pseudo first order model. The thermodynamics parameters also showed that the reaction is endothermic, spontaneous and is randomized. This implies that the reaction of the degradation of MB and 2-NP is feasible and the catalysts prepared have high catalytic activity. MB and 2-NP were degraded to smaller organic molecules (carboxylic acids). The stability of the catalyst observed to decrease as the number of cycles increased, this is due to the leaching of iron ions from the support material. Hence it was concluded that the activated carbon-iron oxide composite was successfully synthesized and had the high catalytic activity for the degradation of MB and 2-NP.
138

The effects of wastewater treatment plant effluent and agricultural runoff on the reproductive systems of fathead minnow, Pimephales promelas

Kromrey, Natalie A., University of Lethbridge. Faculty of Arts and Science January 2009 (has links)
Endocrine disrupting compounds and pesticides have been detected in rivers and irrigation canals of Southern Alberta, a semiarid region with irrigation-dependent crop production, intensive livestock operations, and a growing human population. However, little is known about the effects of agricultural runoff or wastewater treatment plant (WWTP) effluent in Southern Alberta on fish. Reproductive effects of WWTP effluents from the cities of Lethbridge and Medicine Hat, as well as agricultural runoff in the Lethbridge Northern Irrigation District canals, were investigated in a field study with wild fathead minnows (FHMN) in the Oldman and the South Saskatchewan rivers, in Alberta, Canada, and in a laboratory study with laboratory reared FHMN exposed in vivo to the city of Lethbridge WWTP effluent for 21 days. Biochemical and morphological endpoints were measured to characterize reproductive status. Liver vitellogenin, a biomarker of exposure to estrogen mimics, was analyzed using quantitative RT-PCR, and gonadal histology was used to determine sex, gonadal maturity, and intersex. Adverse reproductive effects were detected in FHMN exposed for 21 days to 10 and 25% of Lethbridge WWTP effluent. In the field, effluents from both Lethbridge and Medicine Hat had an effect on the reproductive systems of FHMN. In canals, reproductive effects were detected in wild fathead minnows in years when water quality in irrigation drain canals decreased. Exposure to pesticides was estimated using acetylcholinesterase (AChE) inhibition. Exposure to Lethbridge WWTP effluent did not inhibit AChE, whereas results from the field study were inconclusive. In conclusion, reproductive systems of fathead minnows in Southern Alberta were impacted by anthropogenic chemicals. / xi, 104 leaves : ill. (some col.), maps ; 29 cm
139

Evaluation of the impacts of municipal wastewater treatment on the receiving environment : a case study of the Olifantsvlei wastewater treatment plant in the Gauteng Province, South Africa

Mothetha, Matome Lucky 03 1900 (has links)
South Africa is water scarce country with maximum rainfall received in the summer season which lasts for only three months (November, December and January); hence the water resources have to be protected. The municipal wastewater effluents are considered one of the environmental threats that impact the water quality of the streams. This study was conducted to assess the environmental impact that the wastewater effluent has on the Klip River system, the performance of the plant and also to assess the spatial and temporal variations of water quality along the Klip River system.The study focused mainly on historical data over a five period (2009 – 2013) years secondary data which was analysed by Johannesburg Water Ltd (Pty) and primary data were also collected and analysed using the standard methods of laboratory analysis. The standard methods used include Ion selective electrode, gravimetric techniques, iodemetric titration, membrane filtration method; colorimetric method, automated flow injection method and inductively coupled plasma atomic emission spectrometry (ICP – AES). The aim of collecting the primary data during the dry and wet seasons was to verify the secondary data. The data set was further analysed using multivariate techniques such as principal component analysis (PCA), factor analysis (FA) and discriminant analysis (DA) to determine the spatial and temporal variation of water quality. The data set using ten water quality parameters (ammonia, sulphates, Chlorine, Chemical Oxygen Demand, conductivity, Escherichia coli, sodium, nitrates, pH and suspended solids) was grouped into four sampling points (influent, effluent, downstream and upstream points) and four seasons.Discriminant analysis of water quality showed that out of ten water quality parameters analysed, only sulphates was a less significant parameter to discriminate between the sampling points. For the temporal variations, eight water quality parameters (ammonium, Chlorine, Conductivity, sodium, nitrates, pH, sulphates and suspended solids are the most significant parameters to discriminate between the four seasons. PCA/FA results highlighted similarities in terms of water quality loading between summer and winter seasons and between the winter and autumn seasons. Summer and winter seasons had strong positive loading in COD, ammonium, suspended solids and E. coli whereas the autumn and spring seasons had strong positive loading in sodium, chlorine and pH. The study further highlighted that the Olifantsvlei Wastewater Treatment Works (WWTW) is effectively treating the wastewater up to the required standards before discharging them into the Klip River system. This study concludes that the Olifantsvlei WWTW does not contribute significant loads of pollutants into the Klip river system. / Environmental Sciences / M. Sc. (Environmental Science)
140

Productions of high quality wastewater final effluents remain a challenge in the Eastern Cape Province of South Africa

Gusha, Siyabulela Stability January 2012 (has links)
Water is an indispensible and yet a difficult resource to be renewed, thus water scarcity has become one of the major challenges faced worldwide, with the Southern regions of Africa being the most impacted and affected, especially the Eastern Cape Province of South Africa where rural communities depend on receiving waterbodies that are often negatively impacted by wastewater final effluents. This present study was conducted between August and December 2010 to assess the physicochemical and microbial qualities of the final effluents of peri-urban and rural communities based wastewater treatment plants in the Eastern Cape Province. The physicochemical parameters were determined on site and in the laboratory, while bacteriological qualities were determined using culture based techniques. The virological qualities were determined by molecular methods using reverse transcriptase polymerase chain reaction for the target RNA virus and the conventional polymerase chain reaction for the target DNA virus. For both wastewater treatment plants, the physicochemical parameters ranged as follows: chemical oxygen demand (5.95-45 mg/L); total dissolved solids (114.5-187.0 mg/L); salinity (0.12-0.20 psu); temperature (14.2-25.7oC); pH (6.0-7.6); nitrate and nitrites (1.55-6.7 mg/L and 0.023-1.15 mg/L respectively); biological oxygen demand (3.5-7.8 mg/L); turbidity (1.49-6.98 NTU); and chlorine residual (0-2.97 mg/L). Feacal indicator bacteria counts ranged as follows: feacal coliforms (0-1.25×104 cfu/100 ml); total coliforms (0-3.95×104 cfu/100 ml); and enterococci (0-5.0×103 cfu/100 ml). xviii Seventy five percent of the rural community based plant and 80 percent of the peri-urban community based plant were positive for coxsackie A virus, while hepatitis A virus was detected in all the rural community based plant 80 percent of the peri-urban community based plant. This study suggests the need for intervention by appropriate regulatory agencies to ensure regular monitoring of the qualities of final effluents of wastewater treatment facilities in the Eastern Cape Province and ensure compliance to established guidelines.

Page generated in 0.1358 seconds