Constructed wetlands have been used for over two decades for the treatment of acid mine drainage (AMD). Through a variety of physical, chemical, biological processes, these wetlands are effective in reducing acidity and removing up to 99% of iron and aluminium from AMD, but they only remove 20-30% of the manganese loading. The Slippery Rock Creek watershed in northwestern, Pennsylvania has been adversely impacted by acid mine drainage (AMD) for over 100 years with 74 mine discharges contributing a total of 1,228.8 kg, 282 kg and 69 kg/day of sulfuric acid, iron and aluminium, respectively to receiving streams. In the Slippery Rock Creek Watershed, aerobic and vertical flow wetlands, along with limestone drains and vertical flow limestone beds help to restore acid mine drainage impacted streams. Since 1995, the construction of seven passive treatment systems currently contribute 192.8 kg of alkalinity and remove 39% of the acid loading to a 4.83 km section of Slippery Rock Creek. When the eight passive treatment currently under construction are in operation, it is anticipated that there will be an additional 34.7% reduction in acidic loading to streams within the watershed. The cost of restoring all streams currently impacted by acid mine drainage within the Slippery Rock Creek watershed is currently estimated at $8,929,500.

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