Publications

Level of acid mine drainage disturbance explained more of the variation in diatom communities than any other factor, with pan type second and season not significant. Sulphate and calcium concentrations and sulphate to chloride ratios were higher in disturbed pans of every type. Pan type specific indices were tested against established riverine indices.

Sets out the authorisation route for leaving a pitlake as a closure landform, covering water use licensing, environmental authorisation and the wider legislative process. There is no single application that grants approval, and the route is long and partly duplicated, so several applications are required.

Geophysical logging of boreholes above three Witbank seams identified clay rich matrices, stiffness changes, bedding planes and the principal stress direction, and picked up fractures in 30 to 75 per cent of cases. Core logging found most of the same features faster, so routine use was not recommended unless stiffness and stress direction matter.

Conventional rehabilitation relies on lime, fertiliser and compost to build fertility and select adaptive species, which produces short term cover but rarely a self sustaining ecosystem. The work argues for treating soil microbes as part of the system, since bacteria drive nutrient cycling, organic matter breakdown and soil aggregation, and proposes conditioning plants with adapted rhizosphere bacteria on coal waste substrates.

Rehabilitated opencast soils carried pastures and cash crops, but compaction and cover soil depth set the ceiling on what they could produce. Only land with deep cover soils suited maize and sunflower, and deep ripping with regular tillage was needed. Bulk density standards were not met at the trial sites, which the review judged enough to have changed the results.

A regional monitoring programme was found to be viable and is proposed as a public private partnership covering air emissions, air quality and energy efficiency on the Mpumalanga Highveld. The assessment concluded that the worst health impacts fall on residential areas, driven by inefficient coal burning for heating and by housing sited close to large industry.

Coal can feed products well beyond combustion. The study sets out routes to rare earth elements held in particular seams, building materials made with carbon fibre and carbon char, coal foam and graphene composites, carbon black and activated carbon, including a coal derived activated carbon reported to hold four times the gas of compressed natural gas at lower pressure.

Conventional cost accounting at the mines studied could not report on physical structure or materials flow, so environmental costs such as water, energy and consumables stayed hidden and chances to cut them were lost. Four case studies across different commodities and mining methods showed the same limitations. An environmental management accounting model is proposed to identify and allocate those costs.

Ion exchange converted reverse osmosis brine from a power station treating colliery water and cooling tower blowdown into fertiliser and explosives salts, with no liquid effluent left to dispose of. Part of the water rejected by the reverse osmosis stage was also recovered as potable water. Brine is currently used for dust suppression and stored underground.

Ion exchange treatment of acid mine drainage from a closed KwaZulu-Natal colliery was piloted and shown to give effluent free processing, converting the salts into saleable products rather than sludge and brine. Reverse osmosis had previously produced water of discharge standard but left both. Combined flow from the two mine compartments averaged 4.6 megalitres a day.

Ion exchange applied to brine from a three stage reverse osmosis plant at eMalahleni converted the brine entirely into saleable fertiliser and explosives feedstock, and recovered close to half of the water the reverse osmosis stage leaves behind. On this basis the existing brine pond and the two planned for the plant expansion would not be needed.

Watercourses on post mined land near Kriel showed deterioration in manganese, calcium, magnesium, sodium, total dissolved salts and sulphate, while other parameters stayed within drinking water standards. Aquatic invertebrate communities had suffered significant losses and two sites were classified as eutrophic. The water is not fit for human consumption or recreation, and a minimum 32 m buffer from wetland boundaries is recommended after earthworks.

Section performance was limited by the will and motivation of the workforce, not by equipment, layout or technical competence, all of which were found sound. Team based bonus payments were the strongest motivator and reinforced cooperation across shifts and functions, but dependence on bonus income to meet monthly expenses turned it into a source of stress. Recognition in front of colleagues and family motivated strongly.

Prices for calcium and magnesium sulphate are recorded for South Africa and for world markets as at mid 2012, together with price trends and the groundwater chemistry that governs which salts a mine water stream will yield. The figures were assembled to support feasibility studies on a eutectic freeze crystallisation plant and an ion exchange plant.

Eutectic freeze crystallisation was compared with evaporative crystallisation as a route for treating hypersaline mine brine. Optimised commercial evaporative crystallisers use 40 to 50 kWh per cubic metre of feed. Laboratory work measured a eutectic temperature of -21.1 degrees Celsius for pure sodium chloride solution, and found that a large difference between coolant and solution caused scaling on the heat exchanger wall.

Ion exchange was assessed as a treatment route for brine arising from mine water cleaning, from a market rather than a plant performance standpoint. World demand for ion exchange resins was expected to pass 535 million dollars by 2015, driven by urbanisation, pollution and shortages of clean water in developing regions.