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This research focuses on the remediation of Acid Mine Drainage (AMD) using metallurgical slags. Slag leach beds are a promising low cost and low maintenance technology for the remediation of AMD compared to potentially expensive and maintain once intensive conventional active methods that entail addition of chemicals to treat AMD. Slags are highly alkaline in nature hence they neutralise acidic water; this in turn leads to reduction of iron and sulphate concentration due to formation of iron precipitates and gypsum at higher pH values. Laboratory experiments were carried out to investigate the possibility of reducing acid, iron and sulphate concentration from synthetic AMD using two types of slag namely the basic oxygen furnace and stainless steel slag. These experiments include ratio tests, contact time tests and continuous flow studies. Experiments were performed to determine the optimum slag to AMD ratios that would result in maximum pH increase as well as maximum iron and sulphate reduction. These experiments were carried out by varying the amount of slag in use per 1L of AMD for a given period of time. The ratio tests showed that the amount of iron and sulphate removed as well reduction of acidity increased with an increase in the slag to AMD ratio with both slags used. This was an indication that chemical reaction and precipitation was taking place. It was found that 100 g/L of slag: AMD was the optimum ratio. At that ratio a resultant pH of 12.31, 99.7% iron reduction and 75.0% sulphate reduction was achieved. The reduction of acid, iron and sulphate concentration was rapid in the first hour of mixing slag and AMD in processes carried out to investigate the effect of contact time. It was discovered that reduction gradually decreased with time for all experiments under investigation. The continuous flow studies showed that slags were also capable of reducing acid, iron and sulphate concentration from synthetic AMD in a continuously flowing process. The data collected showed that iron was removed from 1000 mg/L to undetectable concentration while sulphate was reduced from 5000 mg/L to 743 mg/L, which translated to 85.1% decrease for a residence time of 2.0 hours. For a residence of 2.53 hours, sulphate was reduced from 5000 mg/L to 693 mg/L which translated to 86.1% decrease. The pH was also increased from 2.25 to 13.21. The Department of Water Affairs and Forestry (DWAF) standards stipulate that wastewater must have iron concentration less than 0.30 mg/L and sulphate concentration less than 400 mg/L. The results show that iron was reduced below the iv DWAF general limit for wastewater while sulphate was still above that limit. A graph was also created to predict the amount of slag required to treat different AMD flowrates for different residence times and target concentrations of iron and sulphate. The results obtained, it was shown that slags are a viable option to treating AMD. The results also revealed that basic oxygen furnace slag was better than stainless steel slag for reducing acidity, iron and sulp...

Wine production in South Africa is delocalised, with numerous small-to-medium sized producers within several regions within the Western Cape. Whilst adapting to new technological changes, producers have to respond to pressure from consumers and governments regarding the environmental consequences of winemaking, especially water usage and pollution. To date, no systematic analysis integrating the various aspects of winemaking in South Africa has been done. This study assessed both physical inputs and outputs. A detailed questionnaire was developed to broadly assess these parameters and was submitted to all cellars in South Africa. Case studies were performed at three cellars during the 2002 harvest season to validate the questionnaires and collect missing information. Based on this, and a cocurrent project, the following parameters were correlated to the tons of grapes presses per annum: effluent parameters which include chemical oxygen demand, suspended solids, total dissolved solids, sodium adsorption ratio, quantity of effluent; wine produced, water consumed, and electricity consumed. These parameters were used to develop an input/output model. This model may be used by wineries to predict their water and electrical consumption, wine produced and effluent characteristics provided they know the tonnage of grapes pressed per year.

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The mining industry utilises 3% of the total water withdrawn in South Africa and is one of the industries responsible for the deterioration of water quality in South Africa. Mine water requirements can be reduced with correct implementation and/ or improvement of current mine water management strategies. Any reduction in mine water requirements will reduce the demand on current water resources and hence the impact on water quality. The direct water footprint for 2 concentrators, a smelter and a tailings dam of a platinum processing plant were calculated using the Water Footprint Network assessment method. This includes the sum of the blue-, green-and grey-water footprints. Water footprints of chemicals used during flotation were excluded from the scope of the investigation. Water used in change houses and offices was included. /kg PGM. Overall, the total grey-water footprint made the largest contribution, accounting for 73%, the blue-water footprint was the second largest (27%), and there was no green-water footprint.