Heavy Metal Loading in Surface Sediments along the Kawere Stream, Tarkwa, Ghana

Sediment contamination by heavy metals resulting from anthropogenic activities is increasingly becoming a global concern due to the risk it poses to human well-being and ecological integrity at large. The purpose of this study was to assess the heavy metals loading in sediment along the Kawere stream. Ten sediment samples were collected, acid digested and analysed for copper (Cu), lead (Pb), cadmium (Cd), manganese (Mn), zinc (Zn), nickel (Ni), chromium (Cr), cobalt (Co) and iron (Fe) using a Varian AA240FS Atomic Absorption Spectrometer (AAS). The Australian and New Zealand Environment and Conservation Council (ANZECC) guidelines for freshwater sediment quality was used as the benchmark against which the measured metal concentrations were compared. Nemerow’s pollution and potential ecological risk indices were used to evaluate the pollution status and ecological risk levels of the heavy metals in the stream. The results obtained indicated that, except Cu which exceeded the ANZECC trigger value of 65 mg/kg at three sampling sites (K01=171.29 mg/kg, K05=170.83 mg/kg and K07=113.31 mg/kg), all other measured heavy metals concentrations were below their corresponding ANZECC values. Heavy metal pollution assessment showed that three samples (K01, K05 and K07) were slightly polluted, suggesting the likelihood of posing a health threat to the aquatic organisms and humans. Calculated Ecological Risk Index (RI) ranged from 3.229 to 19.750 (RI < 150), representing a low ecological risk. As such, the metals, Cu, Ni, Cd, Pb, Cr, and Zn pose a low ecological risk to the aquatic ecosystem. Although the ecological risk is low based on the current results, constant monitoring of the stream quality is recommended due to the increasing human activities along the stream as well as the sediments ability to accumulate and remobilise heavy metals back into the water column and possibly transferring them through the food chain.   Keywords: Heavy Metals, Sediment, Ecological Risk Assessment, Pollution, Strea

Vacuum Pyrolysis of Waste Vehicle Tyres into Oil Fuel Using A Locally, Fabricated Reactor

Abstract Some countries still face daunting challenges of managing ever-increasing waste generated, especially plastic and waste vehicle tyres.  Whilst some developed countries have adopted innovative ways such as catalytic or pyrolytic decomposition processes for energy or fuel generation from these wastes, developing countries like Ghana still dispose off indiscriminately around communities or un-engineered dumpsites. Hence, this study sought to transform waste vehicle tyres into fuel which invariably minimises or eliminates its environmental impact. Particularly, waste vehicle tyres (sourced from dumpsites in Tarkwa, Ghana) were washed, shredded and decomposed via pyrolysis at high temperature range (~ 450 - 650 oC) using locally designed and fabricated reactor. The physicochemical properties (such as water content, flashpoint, density, sulphur content, solids and viscosity) of the pyrolysis oil produced were also examined using the American Society for Testing and Materials (ASTM) standards and procedures. The results showed that the viscosity, flashpoint and the density of the pyrolysis oil produced were 0.904 cSt, 34.5 oC, and 850.6 kg/m3 (at 15 oC), respectively. The sulphur, water and solids/particulates contents were 4340.0 ppm, 0.8 vol.%, and 483,495.5 ppm, respectively. It was also observed that the pyrolysis oil obtained appeared as thick, single-phase liquid with dark colour and strong odour at room temperature. Relatively, the properties of pyrolysis oil produced without further treatment did not meet the International specification for diesel fuel, hence its usage would require further treatments such as desulphurisation, decanting, centrifugation and filtration. Overall, the study has demonstrated that the pyrolysis of waste vehicle tyres into fuel provides an alternative method for managing end-of-life vehicle tyres and adding value to waste in general.   Keywords: Pyrolysis, Waste Vehicle Tyres, Reactor, Pyrolysis Oil, Biofue

The Use of Bauxite as an Arsenic Filter

AbstractArsenic (As) has the potential to negatively affect soils and groundwater quality, and cause several public health challenges. It is usually concentrated and released during metal mining of ores that contains arsenic-bearing minerals. Remediation strategies are in place to avoid pollution. In this study, bauxite from Awaso, Ghana, was characterised, and its ability to sequester As was tested under varying conditions of temperature, Eh and pH. The study showed that the best particle size in the range utilised was 80% passing 2 mm as it allowed easy percolation, and As removal was about 95%. The reaction is a favourable pseudo-second order reaction that is spontaneous and thermodynamically stable and compares well with the Langmuir Sorption Isotherm. About 80% sorption was achieved within 20 minutes of contact with low desorption rate of less than 1.8%. The study thus concludes that bauxite is a good filter for arsenic. Keywords: Arsenic, Bauxite, Filter, Sorption, Isother