In recent times, surface water resource in the Western Region of Ghana has been found to be inadequate in supply and polluted by various anthropogenic activities. As a result of these problems, the demand for groundwater by the human populations in the peri-urban communities for domestic, municipal and irrigation purposes has increased without prior knowledge of its water quality. Water samples were collected from 14 public hand-dug wells during the rainy season in 2013 and investigated for total coliforms, Escherichia coli, mercury (Hg), arsenic (As), cadmium (Cd) and physicochemical parameters. Multivariate statistical analysis of the dataset and a linear stoichiometric plot of major ions were applied to group the water samples and to identify the main factors and sources of contamination. Hierarchal cluster analysis revealed four clusters from the hydrochemical variables (R-mode) and three clusters in the case of water samples (Q-mode) after z score standardization. Principal component analysis after a varimax rotation of the dataset indicated that the four factors extracted explained 93.3 % of the total variance, which highlighted salinity, toxic elements and hardness pollution as the dominant factors affecting groundwater quality. Cation exchange, mineral dissolution and silicate weathering influenced groundwater quality. The ranking order of major ions was Na(+) > Ca(2+) > K(+) > Mg(2+) and Cl(-) > SO4 (2-) > HCO3 (-). Based on piper plot and the hydrogeology of the study area, sodium chloride (86 %), sodium hydrogen carbonate and sodium carbonate (14 %) water types were identified. Although E. coli were absent in the water samples, 36 % of the wells contained total coliforms (Enterobacter species) which exceeded the WHO guidelines limit of zero colony-forming unit (CFU)/100 mL of drinking water. With the exception of Hg, the concentration of As and Cd in 79 and 43 % of the water samples exceeded the WHO guideline limits of 10 and 3 μg/L for drinking water, respectively. Reported values in some areas in Nigeria, Malaysia and USA indicated that the maximum concentration of Cd was low and As was high in this study. Health risk assessment of Cd, As and Hg based on average daily dose, hazard quotient and cancer risk was determined. In conclusion, multiple natural processes and anthropogenic activities from non-point sources contributed significantly to groundwater salinization, hardness, toxic element and microbiological contamination of the study area. The outcome of this study can be used as a baseline data to prioritize areas for future sustainable development of public wells.

A regenerable calcium-based sorbent was prepared by pelletizing either powdered limestone or calcium sulfate hemihydrate and then coating the pellets with an optimum mixture of powdered alumina and limestone. The pellets were subsequently calcined and treated at high temperature to produce pellets with a calcium oxide core surrounded by a strong, inert porous shell. The crushing strength of the core-in-shell pellets was directly proportional to the shell thickness. The performance characteristics of the sorbent were determined by employing a thermogravimetric analysis system to measure the rate of reaction of individual pellets with small concentrations of H2S at high temperature. The reaction was rapid and directly proportional to H2S concentration. The reaction rate was not affected greatly by the thickness of the pellet shell or by temperature in the range of 840−920 °C. However, the rate was more rapid for hemihydrate-based pellets than for limestone-based pellets. The hemihydrate-based pellets also had the advantage of withstanding repeated loading and regeneration without suffering a significant loss of reactivity, whereas the limestone-based pellets did suffer markedly. A regenerable calcium-based sorbent was prepared by pelletizing either powdered limestone or calcium sulfate hemihydrate and then coating the pellets with an optimum mixture of powdered alumina and limestone. The pellets were subsequently calcined and treated at high temperature to produce pellets with a calcium oxide core surrounded by a strong, inert porous shell. The crushing strength of the core-in-shell pellets was directly proportional to the shell thickness. The performance characteristics of the sorbent were determined by employing a thermogravimetric analysis system to measure the rate of reaction of individual pellets with small concentrations of H 2 S at high temperature. The reaction was rapid and directly proportional to H 2 S concentration. The reaction rate was not affected greatly by the thickness of the pellet shell or by temperature in the range of 840-920°C. However, the rate was more rapid for hemihydrate-based pellets than for limestone-based pellets. The hemihydrate-based pellets also had the advantage of withstanding repeated loading and regeneration without suffering a significant loss of reactivity, whereas the limestone-based pellets did suffer markedly. Keywords Chemical and Biological Engineering

Accurate estimation of groundwater recharge is essential for the proper management of aquifers. A study of water isotope (δ 2 H, δ 18 O) depth profiles was carried out to estimate groundwater recharge in the Densu River basin in Ghana, at three chosen observation sites that differ in their altitude, geology, climate and vegetation. Water isotopes and water contents were analysed with depth to determine water flow in the unsaturated zone. The measured data showed isotope enrichment in the pore water near the soil surface due to evaporation. Seasonal variations in the isotope signal of the pore water were also observed to a depth of 2.75 m. Below that depth, the seasonal variation of the isotope signal was attenuated due to diffusion/dispersion and low water flow velocities. Groundwater recharge rates were determined by numerical modelling of the unsaturated water flow and water isotope transport. Different groundwater recharge rates were computed at the three observation sites and were found to vary between 94 and 182 mm/year (AE max. 7%). Further, the approximate peak-shift method was applied to give information about groundwater recharge rates. Although this simple method neglects variations in flow conditions and only considers advective transport, it yielded mean groundwater recharge rates of 110-250 mm/year (AE max. 30%), which were in the same order of magnitude as computed numerical modelling values. Integrating these site-specific groundwater recharge rates to the whole catchment indicates that more water is potentially renewed than consumed nowadays. With increases in population and irrigation, more clean water is required, and knowledge about groundwater recharge ratesessential for improving the groundwater management in the Densu River basincan be easily obtained by measuring water isotope depth profiles and applying a simple peak-shift approach.

Groundwater quality study of the Birimian, Cape Coast granitoid and the Densu River have been carried out using Water Quality Index (WQI) and multivariate statistics with the aim of determining their suitability for drinking and irrigation. The results showed that the Cape Coast granitoid generally had elevated values of dissolved ions as compared to the Birimian and surface waters. The WQI values were found ranging from 0 to 50 belonging to "excellent" and "good" water quality. The visualization of the WQI distributions using GIS software suggests point source pollution to areas of deteriorating water quality. Chemical indices like percentage of sodium (Na%), sodium adsorption ratio (SAR), residual sodium carbonate (RSC), and permeability index (PI) indicate that the groundwater in the study area are suitable for irrigation. Cluster and Principal Component Analysis with varimax rotation were also used as a complementary tool to help organize and interpret the chemical analysis. Four principal components with eigen-values greater than unity accounting for 73.16% of the variability in the data were delineated. The factor score plot also separated the polluted areas and identified areas with potential deteriorating water quality. Even though the geology is the main factor controlling the presence of the dissolved ions, the study shows an increase in anthropogenic contributions in some areas.