Browsing by Author "Donkor, A.K."
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Item Feasibility study for biogas integration into waste treatment plants in Ghana(Egyptian Journal of Petroleum, 2017-09) Mohammed, M.; Egyir, I.S.; Donkor, A.K.; Amoah, P.; Nyarko, S.; Boateng, K.K.; Ziwu, C.Biogas (anaerobic digestion) technology is one of the most viable renewable energy technologies today. However, its economic efficiency depends on the investment costs, costs of operating the biogas plant and optimum methane production. Likewise the profit level also rests on its use directly for cooking or conversion into electricity. The present study assessed the economic potential for a 9000 m3 biogas plant, as an alternative to addressing energy and environmental challenges currently in Ghana. A cost-benefit analysis of the installation of biogas plant at University of Ghana (Legon Sewerage Treatment Plant) yielded positive net present values (NPV) at the prevailing discount rate of 23%. Further the results demonstrate that installation of the plant is capital intensive. Biogas used for cooking was by far the most viable option with a payback period (PBP) of 5 years. Sensitivity analysis also revealed cost of capital, plant and machinery as the most effective factors impacting on NPV and internal rate of return (IRR). © 2016 Egyptian Petroleum Research InstituteItem Heavy metals in sediments of the gold mining impacted Pra River basin, Ghana, West Africa(Soil and Sediment Contamination, 2005-11) Donkor, A.K.; Bonzongo, J.-C.J.; Nartey, V.K.; Adotey, D.K.Total concentrations of Hg, Al, Fe, As, Pb, Cu, Cr, Ni, Mn, Co, V, and Zn were determined in surface sediments collected from 21 locations within the gold mining impacted Pra River basin in southwestern Ghana. Samples were collected during both the rainy and dry seasons. We hypothesized that in the rural southwestern portion of Ghana, the lack of industrial activities makes artisanal gold mining (AGM) by Hg amalgamation the main source of water resource contamination with heavy metals. Therefore, metals showing concentration trends similar to that of Hg in the studied system are likely impacted by AGM. We found that total-Hg (THg) concentrations in riverine sediments are rather low as compared to other aquatic systems that are impacted by similar mining activities. Measured THg concentrations ranged from 0.018 to 2.917 mg/kg in samples collected in the rainy season and from about 0.01 to 0.043 mg/kg in those collected during the dry season. However, the determination of the enrichment factor (EF) calculated using shale data as reference background values showed signs of severe contamination in most of the sampled sites. In the dry season, THg concentrations correlated positively and significantly to the concentrations of As (r = 0.864, p < 0.01), Cu (r = 0.691, p < 0.05), and Ni (r = 0.579, p < 0.05). Based on our previously stated hypothesis, this could then be an indication of the impact of AGM on ambient levels of these 3 elements. However, the determined concentrations of Cu, and Ni co-varied significantly with Al, suggesting that natural sources do account for the observed levels. Accordingly, both AGM and metal inputs from weathered natural deposits are likely co-responsible for the observed levels of Cu and Ni. In contrast, the lack of correlation between As and Al tends to suggest an impact of AGM on As levels. Overall, our data suggest that besides Hg and to some extent As, the impact of AGM on ambient levels of investigated metals in the gold mining impacted Pra River remains negligible. Finally, the increase in metal concentrations from the dry to the rainy season underlines the impact of changes in hydrologic conditions on levels and fate of metals in this tropical aquatic system. Copyright © Taylor & Francis Inc.Item Mercury in different environmental compartments of the Pra River Basin, Ghana(Science of the Total Environment, 2006-10) Donkor, A.K.; Bonzongo, J.C.; Nartey, V.K.; Adotey, D.K.Artisanal gold mining (AGM) with metallic mercury has a long history in Ghana. It is believed to be over 2000 years old. Today, AGM has escalated in a new dimension consuming about half of the country where gold lode deposits exist along riverbanks or rivers are alluvial-gold rich. The Pra River in southwestern Ghana is a site of on going application of metallic mercury in prospecting gold, and this paper examines mercury (Hg) contamination in the different environmental compartments in its watershed. Samples of water, sediment, soil and biota (i.e., human hair and fish) were collected from locations along the course of the river during the rainy and dry seasons of 2002 and 2003, respectively. Besides the obvious Hg point sources along the Pra and its tributaries, the obtained results show that Hg levels and speciation in the studied aquatic system are controlled by precipitation, which drives the hydrology and differences in flow regimes versus seasons. The seasonal difference in Hg speciation suggests that methyl mercury (MeHg) found in the aqueous phase and riverine sediments is likely of terrestrial origin where its production is favored during the rainy season by high soil water and organic matter content. The use of the enrichment factor (EF) for the assessment of sediment quality indicated moderate to severe contamination of surface sediments in the rainy season, while in the dry season, the EF index indicates nearly no pollution of surface sediments. Accordingly, most of the Hg introduced into this river system is likely transported to depositional downstream terminal basins (e.g. the river delta and the Gulf of Guinea). With regard to biota, Hg measured in hair in the dry period was higher than data obtained on samples collected during the wet period. This could be explained at least in part by the shift in diet as a result of abundance of fish in the local markets and the concurrent increase and more active fishing during the dry season. Mercury data obtained on a very limited number of fish samples collected during the dry period only are also presented. © 2005 Elsevier B.V. All rights reserved.Item Pesticide residues in fruits at the market level in Accra Metropolis, Ghana, a preliminary study(Environmental Monitoring and Assessment, 2011-04) Bempah, C.K.; Donkor, A.K.A number of pesticide residues in fruits were monitored at five markets in the Accra Metropolis for almost a year. Locally produced fruits (pawpaw and tomato) and imported apple were purchased from these selected markets in the metropolis and analyzed for pesticide residues by gas chromatography equipped with electron capture detector. In all, 320 sampled fruits were extracted and analyzed for pesticide residues, mainly organochlorines (γ-HCH, δ-HCH, aldrin, heptachlor, γ-chlordane, heptachlor epoxide, α-endosulfan, p,p′-DDE, endrin, β-endosulfan, o,p′-DDT, endrin aldehyde, p,p′- DDT, endrin ketone, and methoxychlor). The data revealed that 32.8% of the fruit samples analyzed contained residues of the monitored insecticides above the accepted maximum residue limit (MRL) whereas 48.7% were below the MRL. Nonetheless, the continuous consumption of such fruits with modest pesticide levels can accumulate and could result in deadly chronic effects. © 2010 Springer Science+Business Media B.V.