Thesis (M.S.)--Ohio University, November, 2008. / Title from PDF t.p. Includes bibliographical references.

This study evaluated the effect of chemical oxidation on the bioremediation of polycyclic aromatic hydrocarbons (PAHs) contaminated sediments. Sediments were treated in sequential steps: biotreatment, chemical oxidation, and biotreatment. The first biotreatment step was initiated via addition of nutrients, microbial seeds, co-metabolites, and/or Tween 80 (surfactant). The chemical oxidation step was conducted using Fenton?s Reagent, ozonation, and peroxone (combination of ozone and hydrogen peroxide). The objective was to enhance the PAHs bioavailability via oxidation of natural organic matter and transformation of Heavy PAHs into more biodegradable compounds. Biotreatment was reestablished as a final polishing step to further degrade remaining PAHs and more biodegradable oxidation by-products. The proposed mechanism was proven successful for the less contaminated sediment (Scioto River) and not the highly contaminated and chemically more complex sediment (Lake Superior). Given this mechanism only worked for the Scioto River sediment, further research is required to determine the mechanisms limiting treatment.

No description available.

Contaminants introduced in solution to coastal waters eventually accumulate in sediment. Pollution by these contaminants is only evident when biological effects occur. Geochemical procedures lack the ability to identify biological effects of pollution. Biological methods (i.e. community structure analyses and/or bioassays) are currently the best available techniques for pollution assessment. Standardised and locally relevant protocols for pollution assessment are lacking in many developing countries, including South Africa. This study aims to develop a sediment toxicity testing protocol using an amphipod species endemic to South Africa, Grandidierella lignorum. Initial research focussed on establishing ranges of physico-chemical parameters (i.e. salinity, temperature, sediment grain size and organic matter content) within which sediment toxicity tests should be performed. The sensitivity of the amphipod was then determined by exposing the amphipod to cadmium, copper and zinc at various salinities. Lastly, the amphipod was exposed to effluents (to test the amphipod’s sensitivity in water only tests) and whole sediment (to tests the amphipod’s sensitivity to solid phase material). G. lignorum tolerates salinities between 0 and 56, but prefers salinities between 7 and 42. Preferred salinity range is modified by temperature, with salinity of 42 becoming less tolerable. Salinities between 7 and 35 are most preferred at 10-25°C. G. lignorum prefers fine- (27.48±12.13%), medium- (25.11±12.99%) and coarse-grained sand (21.45±8.02%). Sediment with low (≤2%) organic matter content is most preferable, regardless of sediment grain size or type of organic matter (protein-rich vs. carbohydrate-rich). Cadmium toxicity decreased with increasing salinity (LC₅₀: 0.34 ± 0.17 mg l⁻¹ (salinity of 7), 0.73 ± 0.05 mg l⁻¹ (salinity of 21) and 1.08 ± 0.49 mg l⁻¹ (salinity of 35)). Zinc toxicity increased with decreasing salinity (1.56 ± 0.33 mg l⁻¹ at a salinity of 21 to 0.99 ± 0.13 mg l⁻¹ at a salinity of 7) and with increasing salinity (from salinity of 21 to 0.82 ± 0.19 mg l⁻¹ at a salinity of 35). Copper toxicity did not differ significantly with salinity and ranged between 0.72 ± 0.18 mg l⁻¹ (salinity of 35) and 0.89 ± 0.24 mg l⁻¹ (salinity of 21). Toxicity testing using Grandidierella lignorum should be performed in coarse- to fine-grained sediment at salinities of 7 - 35, at 10 – 25°C. Amphipods do not need to be fed during toxicity testing. A control chart using cadmium as a reference toxicant was established to determine the acceptability of toxicity results. Toxicity test results should be accepted when cadmium toxicity falls between 0.49 and 4.02 mg l⁻¹. The amphipod responded consistently to effluents and was able to discriminate polluted and unpolluted sediment in Durban Bay. Recommendations for refining the effluent and sediment toxicity test are suggested. / Ph.D. University of KwaZulu-Natal, Durban 2013.

No description available.

Thesis (MScEng (Process Engineering))--Stellenbosch University, 2008. / A substance called CRUD (Chalk River Unidentified Deposit) was deposited together with gold tailings to the East Paydam tailings dam. Previous research conducted on the material has shown that the crud leaches Mn and Ni at concentrations that are above their acceptable risks limits as well as Zn which leaches at concentration slightly below its acceptable limits thereby posing an environmental risk. The main objective of the research was to test the hypothesis stating that soil washing in series with bioremediation can be used to remove the heavy metals from the material from the East Paydam tailings dam. Various laboratory and pilot scale tests were conducted to investigate critical soil washing and bioremediation parameters and their respective influence on the treatment process. Laboratory work involved column tests and batch tests. These tests were crucial in determining the critical parameters for the pilot scale tests such as the selection of the suitable lixiviant from the four that were investigated. The optimal concentration of the lixiviant was also determined together with the optimum soil: liquid ratio. These parameters were employed in the pilot scale tests. Pilot scale tests involved soil washing in series with bioremediation. The bacterial growth over the bioremediation period was also determined. Precipitation of the heavy metals from leachate was investigated by varying the pH and temperature. Results showed that the soil from the East Paydam can effectively be treated by soil washing in series with bioremediation. Oxalic acid was selected for soil washing of the payable slimes at a concentration of 0.001M. However, material that contains high amount of CRUD (deeper down the slime dam) required the relatively concentrated 0.1M oxalic acid and mechanical agitation. Bioremediation was determined to increase the amount of heavy metals that was leached from the material from the East Paydam slimes dam. Precipitation of the heavy metals at a pH of 12 achieved up to 98% removal of heavy metals from leachate.

published_or_final_version / Ecology and Biodiversity / Master / Master of Philosophy

In this work two inverse methodologies are developed based on the Green element method for the recovery of contaminant release histories and reconstruction of the historical concentration plume distribution in groundwater. Unlike direct groundwater contaminant transport simulations which generally produce stable and well-behaved solutions, the solutions of inverse groundwater contaminant transport problems may exhibit non-uniqueness, non-existence and instability, with escalation in computational challenges due to paucity of data. Methods that can tackle inverse problems are of major interest to researchers, and this is the goal of this work. Basically, the advection dispersion equation which governs the transport of contaminants can be handled by analytical or numerical methods like the Finite element method, the Finite difference method, the Boundary element method and their many variants and hybrids. However, if a numerical method is used to solve an inverse problem the resulting matrix is ill-conditioned requiring special techniques to be employed in order to obtain meaningful solutions. In view of this we explore the Green element method, which is a hybrid technique, based on the boundary element theory but is implemented in an element by element manner. This method is attractive to inverse modelling because of the fewer degrees of freedom that are generated at each node. We develop two approaches, in the first approach inverse Green element formulations are developed, the ill-conditioned matrix that results is decomposed with the aid of the singular value decomposition method and solved using the Tikhonov regularized least square method. The second approach utilizes the direct Green element method and the Shuffled complex evolutionary (SCE) optimization method. Finally, the proposed approaches are implemented to solve typical problems in contaminant transport with analytical solutions besides those that have appeared in various research papers. An investigation on the capability of these approaches for the simultaneous recovery of the source strength and the contaminant concentration distribution is carried out for three types of sources and they include boundary iv sources, instantaneous point sources and continuous point sources. The assessment accounts for different transport modes, time discretization, spatial discretization, location of observation points, and the quality of observation data. The numerical results demonstrate the applicability and limitations of the proposed methodologies. It is found in most cases that the solutions with inverse GEM and the least squares approach are of comparable accuracy to those with direct GEM and the SCE approach. However, the latter approach is found to be computationally intensive.

Photolysis utilises short wavelength ultraviolet radiation to excite and cleave the carbon-chlorine bond of PCBs, yielding less chlorinated PCBs and ultimately biphenyl which can serve as energy and carbon source of various bacteria. Thus integration of photolysis and biodegradation can be a feasible remediation for PCB contamination. / Polychlorinated biphenyls (PCBs) are ubiquitous environmental pollutants once used as industrial fluids (in hydraulic systems, gas turbines), dielectric fluids (capacitors, transformers), plasticizer (adhesives, textiles, sealants, copy paper), and heat exchangers due to their inertness as well as thermal and electrical insularity. However, they are found to be neurotoxic, immunosuppressive, hepatotoxic, and the USEPA classified PCBs as probable human carcinogens. Although the production of PCBs was banned by the US Congress in 1976, they persist in the environment because of their resistance. Upon entering the marine environment, PCBs will associate with particulates and ultimately with sediment due to their hydrophobic nature and thus sediment become a sink for PCBs. This exerts a threat to marine organisms and human who consume seafood. / The major sink of PCBs in the environment is marine sediment, and the presence of sediment particles as well as other sorbed chemicals may inhibit both photolysis and biodegradation. This study extracts PCBs from sediment and further purify them by various cleanups to prevent the effect of these materials on the efficiency of treatment. / Using 2,4,4'-trichlorobiphenyl (PCB 28), 2,2',5,5'-tetrachlorobiphenyl (PCB 52), 2,2',4,5,5'-pentachlorobiphenyl (PCB 101), 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153) and 2,2',3,4,4',5,5'-heptachlorobiphenyl (PCB 180) as model compounds, optimal UV intensity, reaction time, as well as reaction solvent were found to be dependent on the congeners used. While PCB 28 was highly reactive and PCB 101, PCB 153 and PCB 180 were comparatively easy to remove, PCB 52 showed high resistance towards photolysis. The photolysis of PCB mixture containing these five congeners with each of them in 1 mg/L was also being optimised. After optimisation, the reaction intermediates and products were identified by gas chromatography coupling mass spectrometry (GC-MS). Less chlorinated congeners and biphenyl were found, indicating stepwise dechlorination of PCB is the major pathway. (Abstract shortened by UMI.) / by Wong Kin Hang. / "August 2005." / Adviser: P. K. Wong. / Source: Dissertation Abstracts International, Volume: 67-01, Section: B, page: 0159. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 111-140). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Tez (Yüksek Lisans) - Süleyman Demirel Üniversitesi, Fen Bilimleri Enstitüsü, Tekstil Mühendisliği Anabilim Dalı, 2008. / Kaynakça var.