Diffuse pollution associated with the mining sectors in South Africa: a first-order assessment.

Internationally it has become recognised that diffuse source water pollution from mining activities severely affects the degradation of water quality especially with regards to acidification and metal loading. South Africa is facing major problems with regard to the management and treatment of contaminated mine water. Very little has been published for South Africa about the quantities and qualities of diffuse source water pollution by the mining industry. Furthermore the available information has not yet been compiled into a consolidated overview that presents the total picture. Some of the problems that limit the use of the available information and would necessitate further processing to normalise the data, derive from the fact that the investigations producing the information were done at different times, to different levels of detail and using different approaches. A further complicating factor is that data for some mining commodities may not be available and may necessitate further investigation. The overview of the quantities and qualities of non-point source effluent production by different sectors needs to be interpreted in terms of the effect the effluent can be expected to have on receiving water quality (both surface and groundwater). It would thus be necessary to categorise waste types according to their effect on water quality and synthesise the data to obtain an estimate of the threat that different sectors and sub-sectors pose to receiving water quality.

Chemical characterisation of organic electron donors for sulfate reduction for potential use in acid mine drainage treatment.

The production of acid mine drainage (AMD) containing high amounts of sulfate, heavy metals and low pH is of increasing concern. AMD is highly corrosive and results in economic and environmental problems. Organic electron donors for sulfate reduction were chemically characterised for potential use in AMD treatment. This was done in a process to develop a correlation between chemical composition and the capacity to drive sulfate reduction. Potential organic electron donors for sulfate reduction were chemically characterised in terms of dry matter content, ash content, total Kjeldahl nitrogen, lignin content, cellulose content, crude fat, crude fibre, in vitro digestibility, water-soluble carbohydrates, total non-structural carbohydrates and starch content. The chemical composition of the organic electron donors was then compared to results obtained from pilot plant studies where the organic electron donors for sulfate reduction were evaluated in terms of sulfate reduction. The chemical composition of the carbon source severely impacted its capacity to drive sulfate reduction and may be used to assist in predicting the sulfate reduction capacity of a carbon source. Organic electron donors for sulfate reduction high in protein content and low in lignin content or high in carbohydrate and crude fat content increased the capacity of a carbon source to drive sulfate reduction. The higher the fibre content of a carbon source, the lower the capacity to drive sulfate reduction. No correlation could be drawn between % dry matter, % ash content and sulfate reduction for the organic electron donors tested. Chemical characterisation can be used to assist in predicting sulfate reduction capacity of organic electron donors.

Biofouling and biocorrosion in industrial water systems.

Corrosion associated with microorganisms has been recognized for over 50 years and yet the study of microbiologically influenced corrosion (MIC) is relatively new. MIC can occur in diverse environments and is not limited to aqueous corrosion under submerged conditions, but also takes place in humid atmospheres. Biofouling of industrial water systems is the phenomenon whereby surfaces in contact with water are colonized by microorganisms, which are ubiquitous in our environment. However, the economic implications of biofouling in industrial water systems are much greater than many people realize. In a survey conducted by the National Association of Corrosion Engineers of the United States ten years ago, it was found that many corrosion engineer did not accept the role of bacteria in corrosion, and many of then that did, could not recognize and mitigate the problem. Biofouling can be described in terms of its effects on processes and products such as material degradation (bio-corossion), product contamination, mechanical blockages, and impedance of heat transfer. Microorganisms distinguish themselves from other industrial water contaminants by their ability to utilize available nutrient sources, reproduce, and generate intra- and extracellular organic and inorganic substances in water. A sound understanding of the molecular and physiological activities of the microorganisms involved is necessary before strategies for the long term control of biofouling can be format. Traditional water treatment strategies however, have largely failed to address those factors that promote biofouling activities and lead to biocorrosion. Some of the major developments in recent years have been a redefinition of biofilm architecture and the realization that MIC of metals can be best understood as biomineralization.