Phytoremediation is thought to be the most sustainable wastewater treatment option for developing countries. However, its application is often limited by unavailability of suitable candidate species. In the present study, the potentials of Limnocharis flava, Thalia geniculata and Typha latifolia for remediation of heavy metal contaminated wastewater with a constructed wetland system were evaluated. The wetland consisted of three treatment lines each planted with sufficient and equal number of a species. Duplicate plant and water samples were collected bi-monthly and analyzed for Fe, Cu, Zn, Pb, and Hg using the atomic absorption spectrophotometer over a six month period. Bioaccumulation rates generally increased over time and varied among plants for these metals, with Fe (456-1549 mg kg1 roots; 20-183 mg kg(-1) shoot) being the most sequestered and Pb (1.2-7.6 mg kg(-1) roots; 1.55-3.95 mg kg(-1) shoot) the least. Translocation factors differed among the species but generally remained stable over time. L flava showed potential for hyperaccumulating Hg. Removal efficiencies varied for the studied metals (approximately 20-77 %) and were generally related to metal uptake by the plants. These results demonstrate the suitability of the species for phytoremediation, and the usefulness of the technique as an option for improving irrigation water quality in Ghana.
The exploration and production of petroleum resources is not without environmental consequences and these remain an important factor in contemporary global oil industry. As an emerging oil producing nation, very little or nothing is known about the behaviour of Ghana's sweet light crude in water under varying environmental conditions. This is crucial for an efficient management of accidental spills. Therefore, this study designed a deterministic model for oil spill trajectory simulation using the Saltpond oilfield (Ghana) as study location. The main objectives were to: (a) design a diagnostic GNOME model to configure and generate localised oil spill scenarios; (b) model different oil spill scenarios and weathering profiles for varying environmental conditions e.g. wet/dry seasons, different currents and wind conditions; and (c) Predict the 'minimum regret' Splots as a precautionary principle. A combined Eulerian-Lagrangian approach involving a hydrodynamic model containing localised environmental parameters from the Saltpond oilfield was utilised. The General NOAA Operating Modelling Environment (GNOME) based on a Cϩϩ programming language was used to execute the analyses. In addition, the ADIOS2 oil weathering tool was used to estimate the oil budget for different spill quantities based on the physical and chemical properties of Ghana's sweet light crude at Saltpond field. The key findings are: 5000 and 10,000 barrels of spilled oil beached after a minimum of 12 hours in 97% of the scenarios under the influence of winds from the South. Wind speeds leading to beaching were 35.7% for 14 and 16 knots, 14.3% for 17 knots and 7.1% for 15 and 20 knots respectively. Weathering results showed a maximum of 43% of spilled oil evaporated after 116 hours with a minimum and maximum dispersal of 1% and 7% respectively. This study, for the first time, has provided hitherto unavailable analysis and information on oil spill transport forecasting and trajectory simulation for the Saltpond Oilfield in Ghana which environmental managers/engineers would find readily useful in responding to future oil spill disasters. The approach and methodology used in this study could also be adapted for other offshore regions in Ghana and West Africa.
Produce water treatment and discharge is a critical public health issue in most oil producing countries, where efficient and economical treatment options are being sought after. The main focus is centred on the removal of heavy metals and hydrocarbon residues. Phytoremediation, the technique that utilizes a plant's inherent ability to accumulate metals, is fast emerging as a relatively cheap and environmentally friendly alternative to conventional wastewater treatment methods. A corollary of this is an urgent need to identify plant species with the appropriate suite of characteristics for phytoremediation. The purpose of this study was to evaluate and compare the phytoremediation potentials of Limnocharis flava, Thalia geniculata and Typha latifolia using three serially connected horizontal sub-surface flow (HSF) constructed wetlands. Each wetland had only one of the three plant species but all were supplied with wastewater from a common source. From October 2010 to March 2011, the growth performance of the candidate plants was measured, and their accumulation and translocation rates of heavy metals (Fe, Cu, Zn, Pb, Hg) determined using atomic absorption spectrophotometer. Mean removal efficiencies ranged from 40-80%, 48-54%, 44-54%, 18-32% and 8-38% respectively for Fe, Hg, Zn, Pb and Cu. The removal efficiencies of the species differed depending on the metal. L. Flava was most efficient (p<0.001) at removing Fe, Cu mostly removed by T. latifolia (p< 0.001) whilst T. geniculate appeared to be the best remover of lead (p< 0.021). Both T. geniculata and T. latifolia appeared to remove zinc better than L. flava (p<0.021), but there was no statistical difference in the removal rates of mercury by the plants. Similar trends were observed for the bioaccumulation factor, which increased substantially with time. The plants accumulated most of the metals in their roots. The findings demonstrate the capabilities of the three phytoremediants for improving the quality of heavy metal contaminated water.
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