Treatment method | Requirements | Construction | Design factors |
Ponds | Net alkaline water | None | None |
Aerobic wetlands | Net alkaline water | Overland flow with cattails | 10 - 20 g Fe/m2/day 0.5 - 1 g Mn/m2/day |
Anaerobic wetlands | Net acidic water Low flow | Flow over and within the substrate | 3.5 g acidity/m2/day |
Sulfate-reducing bioreactors | Net acidic water low flow | Flow through the substrate | Residence time of 24 h |
ALD | Net acidic water low DO, Al, Fe contents | Flow through buried limestone | Residence time of 15 h |
SAPS | Net acidic water | Vertical flow | 15 - 30 cm of organic matter, residence time of 15 h, 20 g acidity/m2/day |
Open limestone drain | Slope > 10% | Rock-lined channel | Acid load and residence time |
Limestone leach bed | Inflow pH < 3.0 | Flow through limestone | Residence time of 1.5 h |
Slag leach bed | Water without metals | Flow through steel slag fine aggregate | Residence time of 1 - 3 h |