Sustainable Development of the Waterberg Coalfields

Irrigation with calcium and sulphate rich mine water proved feasible and sustainable over eight years at a Mpumalanga colliery, with no significant impact on soil, surface water or groundwater. Sugarbeans, wheat, maize, potatoes and pastures were grown on a commercial scale. High calcium and magnesium suppressed potassium uptake, and waterlogging from poor site selection was the main problem.

Co-treating coal discards with sewage sludge by hydrothermal carbonisation gave hydrochars with better physicochemical properties than treating either waste alone. The blended hydrochar reached a surface area of 20.35 m2/g and a pore volume of 0.38 cm3/g, and removed 97.19% of nevirapine and 93.32% of lamivudine from recycled water. Routes to activated carbon and hydrogen storage were also assessed.

No standard technique for predicting, controlling or extinguishing spontaneous combustion emerged, and the methods in use proved expensive and not routinely successful. Because every mine differs, the work sets out a sequence of locating the fire, assessing the risk, choosing a strategy and method, then monitoring it. Separate control measures are given for old workings, exposed coal and spoil heaps.