Water

Hydrogen for biological sulphate removal can be generated on site by electrolysis more cheaply than it can be bought. Stainless steel electrodes in acid mine drainage gave hydrogen at about a third of the bought in price while oxidising ferrous iron to ferric, which helps downstream treatment. Iron and zinc electrodes dissolved too quickly to be viable.

Heat exchanger material governs how fast ice scale forms during eutectic freeze crystallisation of dilute brine. Induction time fell as thermal conductivity rose, so copper scaled first, while aluminium gave the lowest scaling rate because its low surface energy pushed ice crystallisation into the bulk. Stainless steel delayed onset but scaled heavily once nucleation started.

Compared against concrete and gabions on cost, construction time, footprint, durability and safety, the Dongalock product proved cheaper and quicker to install in small and medium incised valley bottom wetlands, and needs no heavy plant, so local enterprises can build it. Concrete still suits large wetlands carrying high water velocities.

A digital wetland map and linked database were compiled for the Upper Olifants River Catchment from existing literature, existing wetland layers and aerial photography. Wetlands cover about 2 147 km2, some 14 per cent of the 15 158 km2 catchment. The wetland layer is about 70 per cent accurate and its attributes about 60 per cent, so it suits baseline screening rather than site assessment.

Ecological integrity of a Mpumalanga wetland affected by coal mining was assessed before and after rehabilitation, using water quality, bacterial consortium, freshwater algae and vegetation indicators. The work sits within a wider programme to give the coal sector and regulators practical ways of limiting and mitigating mining impacts on wetlands.