Theses and dissertations (Applied Sciences)
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Item The efficiency of phytoremediation using Panicum maximum and TiO2 nanoparticles(2021) Cibane, Nozipho Sinenhlanhla; Mdluli, Phumlani Selby; Moodley, K.G.; Arthur, G.D.This study focused on the application of Panicum maximum (guinea grass) for evaluating the phytoremediation of titanium dioxide nanoparticles (nTiO2). This study was done to explore the ability of Panicum maximum Jacq as a hyperaccumulator for phytoremediation of nTiO2. Titanium dioxide has steadily become more abundant in our environment over the years due to human activities, and this could potentially harm the environment. Panicum maximum (guinea grass) is a non-vascular plant with a short life cycle. It is well adapted to a wide variety of conditions. It originated from Africa but is presently found and cultivated in almost all parts of the world with tropical climates. It is loosely to densely tufted, with short rhizomous rooting at the lower nodes. Leaf blades are linear to narrowly lanceolate. Plant to metal oxide nanoparticle interaction was investigated by germination of seeds in the presence of titanium dioxide nanoparticles (nTiO2). The uptake of nTiO2 by Panicum maximum Jacq was evaluated after treatment of the seedlings with nTiO2. The synthesized nTiO2 was characterized, using Transmission Electron Microscope, Scanning Electron Microscope. Energy Dispersive Spectroscopy (EDX), and X-ray Diffraction (XRD). The average mean particle distribution was analyzed using Image J. The Image J analysis showed that the average particle distribution of nTiO2 was 9 nm. The TEM and SEM results revealed that the particles in the nTiO2 were spherical in shape. The XRD analysis revealed that the nTiO2 was predominantly 67.1% and 32.9% of anatase and rutile forms, respectively. Metal uptake was analyzed using the Inductively Coupled Plasma – Optical Emission Spectrometer method (ICP-OES) after the plants were digested using the wet digestion and microwave digestion methods. The ability of the plants to translocate the metals to the aerial parts of the plants (Translocation Factor - TF) was evaluated for the metal using concentration ranging from 5 ppm to 50 ppm. It was observed that the root had the highest concentration of nTiO2 while the lowest uptake was found in the leaf. The TF was highest for the 5 ppm sample. The roots with the shortest length, which indicated stress/toxicity were that of the plants which were treated with 50 ppm of nTiO2. These also had the highest accumulated nanoparticles which suggested that these plants were negatively impacted by a higher concentration of nTiO2. The standard with 5 ppm treatment showed the highest value of the translocation factor which suggested that at this concentration the nanomaterial aided and catalyzed the movement of nanoparticles to the aerial parts of the plant. The results suggested that seed treated with nanoparticles before planting for phytoremediation purposes could increase the metal uptake selectivity.Item Assessment of heavy metals and pathogens removal from municipal wastewater using a constructed rhizofiltration system(2018) Odinga, Christine Akinyi; Swalaha, Feroz Mahomed; Bux, Faizal; Otieno, Fredrick Alfred O.Wastewater discharged from municipal treatment plants contain a mixture of organic contaminants, trace metals, enteric pathogens, viruses, and inorganic materials. The presence of such pollutants in wastewater poses a huge challenge to the choice and applications of the preferred treatment method. Conventional treatment methods are inefficient in the removal of some environmentally toxic pollutants and pathogens. This study evaluated the effectiveness of a constructed rhizofiltration system in the removal of heavy metals and enteric pathogens from municipal wastewater. The study was conducted at an eThekwini municipal wastewater treatment plant in Kingsburgh - Durban in the province of KwaZulu-Natal. The pilot-scale rhizofiltration unit included three different layers of substrates consisting of medium stones, coarse gravel and fine sand. The system had one section planted with Phragmites australis and Kyllinga nemoralis while the other section was unplanted and acted as the reference section. Influent and effluent, plant tissue and sediment from the rhizofilter were sampled bi-monthly for a period of two years and assessed for the presence and removal of selected enteric pathogens, trace heavy metals and changes in physicochemical and biological parameters using standard methods. Antibacterial potential of the two experimental plants was determined by the agar-well diffusion method using plant root exudates exposed to selected pathogenic bacteria. Observation of details of plant morphology, distribution and assessment of the metals attachment onto the various plant tissues was determined using images from scanning electron microscopy (SEM). The Langmuir model was used to assess the heavy metal adsorption of the plants. There was an increase in pH from 6.95 pH units to 7.55 pH units in the planted and 6.72 to 7.23 pH units in the reference sections. There was an average reduction in biochemical oxygen demand (BOD) by 79% and chemical oxygen demand (COD) by 75%. Suspended solids were reduced by 86% in the planted section and 59.8% in the reference section, Electrical conductivity was reduced by 7.7% in the planted section and 0.83% in the reference section, Total Dissolved Solids was reduced by 11.5% in the planted section and 3.5% in the reference section, temperature was reduced by 11.9% in the planted section and 1.2% in the reference section, while dissolved oxygen was raised by 10% in the planted section and 5% in the reference section. Turbidity was reduced by 9.7 NTU in the planted section and 9.1 NTU in the reference section, while alkalinity was reduced by 46.3% in planted and 45.5% on reference sections of the rhizofilter. There was a significant reduction in organic loading in the system which was statistically significant (phosphorous, p = 0.029; ammonia, p = 0.03).These average reductions and increases were observed after the system was fully established. The results indicate a comparatively better removal efficiency in the planted than the reference sections of the system. Considering the entire rhizofilter, heavy metals were accumulated at varying percentages of 96.69% on planted and 48.98% in reference sections for cadmium. Chromium was 81% and 24%, Copper was 23.4% and 1.1%, Nickel was 72% and 46.5, Lead was 63% and 31%, while Zinc was 76% and 84% in the planted and reference section of the rhizofilter respectively. The planted section had a much higher removal efficiency as compared to the reference section of the rhizofilter. The macrophytes were found to display some metals binding potential according to observations from SEM and EDX analysis. Significant amounts of Cu deposits were recorded on the roots of K. nemoralis at 0.31wt% with a peak at 0.6cps/eV than on P. australis which was at 0.31wt% with a peak at 0.6cps/eV. Further, higher deposits of Ni at 0.01 wt% with peak at 0.5 cps/eV and 0.0 wt% with peak at 0.2 cps/eV, Pb at 0.22 wt% with peak at 0.2 cps/eV and 0.21wt% with peak at 0.2 cps/eV were recorded on the roots of K. nemoralis and P. australis respectively. Kyllinga nemoralis was found to have greater metals adsorptive capabilities than P. australis. The planted and reference sections had varied removal capacities of between 45% and 98% for the various pathogens detected in the influent wastewater. For example, the concentration of coliphage was reduced by 94.6% in the planted section and 93.6% in the reference section, Candida spp. removal was 64.7% in the planted section and 62.5% in the reference section. Escherichia coli was reduced by 65%- 85% while Salmonella spp. was removed by 94% in the planted section compared to 78% in the reference section. Ascaris lumbricoides was reduced by 77% in the planted section and 53% in the reference section. Accordingly, higher pathogens reduction was achieved in the planted section as compared to the reference section of the rhizofilter. Root exudates from Kyllinga nemoralis were found to display a wider zone of growth inhibition at 9.97±0.19 mm compared to P. australis which had a zone of 8.63 ± 0.22 mm when exposed to cultured colonies of Escherichia coli.Item Phytoremediation of heavy metals using Amaranthus dubius(2008) Mellem, John JasonPhytoremediation is an emerging technology where specially selected and engineered metal-accumulating plants are used for bioremediation. Amaranthus dubius (marog or wild spinach) is a popular nutritious leafy vegetable crop which is widespread especially in the continents of Africa, Asia and South America. Their rapid growth and great biomass makes them some of the highest yielding leafy crops which may be beneficial for phytoremediation. This study was undertaken to evaluate the potential of A. dubius for the phytoremediation of Chromium (Cr), Mercury (Hg), Arsenic (As), Lead (Pb), Copper (Cu) and Nickel (Ni). Locally gathered soil and plants of A. dubius were investigated for the metals from a regularly cultivated area, a landfill site and a sewage site. Metals were extracted from the samples using microwave-digestion and analyzed using Inductively Coupled Plasma – Mass Spectroscopy (ICP-MS). Further experiments were conducted with plants from locally collected seeds of A. dubius, in a tunnel house under controlled conditions. The mode of phytoremediation, the effect of the metals on the plants, the ability of the plant to extract metals from soil (Bioconcentration Factor - BCF), and the ability of the plants to move the metals to the aerial parts of the plants (Translocation Factor - TF) were evaluated for the different metals. Finally, A. dubius was micro-propagated in a tissue culture system with and without exposure to the metal, and the effect was studied by electron microscopy.