USE OF PASSIVE TREATMENT SYSTEMS TO MITIGATE THE IMPACT OF ACID-MINE GROUNDWATER DISCHARGES ON RECEIVING STREAMS

摘要

The project area comprises the 70 km~2 headwaters drainage basin of Slippery Rock Creek in Northwestern Pennsylvania. Slippery Rock Creek and its tributaries have been adversely impacted by acid mine drainage for over a 100 years and, at present, over 75 groundwater discharges from abandoned coal mines have been identified within the watershed and, of these, 59 are contributing acid load to receiving streams. The pH values of these streams range from 2.5 to 6.0, with acidity exceeding alkalinity and iron, manganese and aluminum concentrations varying from 2.0 to over 100 mg/L. To date, 15 passive treatment systems have been installed which are removing 30% of the acid loading and contribute 193 kg/day of alkalinity to Slippery Rock Creek and its tributaries. In addition, these systems are effective in removing over 27% of the iron and aluminum to receiving streams. The total cost of the 15 treatment systems is nearly $2.1 million, with an estimated additional $7.9 million being required to mitigate all acidic discharges within the project area.