Unlike net alkaline minewater that can in certain cases be readily treated in aerobic wetlands, net acid minewater requires distinct treatment. Treatment can potentially be achieved using a Successive Alkalinity Producing System (SAPS) which comprises passing the minewater vertically through a layer of substrate overlying a limestone bed. Assessment of such a system used to treat a minewater discharge in South Wales, UK indicates that iron removal is aerobic resulting in accumulation of surface ochre precipitates. As a result, this leads to a reduction in vertical bed permeability. Without on-going management, this can cause over-spill of the SAPS. Successful long-term treatment using systems such as a SAPS requires on-going management and they should not be considered a walk-away option.
