Field investigations of passive and active processes for acid mine drainage Treatment: Are anions a concern?

Abstract

Acid mine drainage (AMD) treatment processes were investigated for removal of anions including bromide, fluoride, chloride, nitrate, phosphate, and sulfate. The study selected a passive process consisting of an aerated lagoon and aerobic wetlands and an active process composed of a lime dosing silo and a sedimentation pond. The results showed both processes were capable of removing fluoride, nitrate, and phosphate. The passive process removed 21% bromide and 26% chloride as a result of biotic mechanisms which could not be achieved by the active process. Additionally, higher temperature and longer hydraulic retention time promoted the removal of many anions. With abiotic mechanisms such as precipitation, the active process was capable of removing sulfate, which was found unsuccessful by the passive process due to unfavorable conditions for the growth of sulfate reducing bacteria. Although the anions in the AMD waters were not high enough to generate substantial environmental and health concerns, their removals, especially the removals of bromide, phosphate and sulfate, would reduce burdens at downstream drinking water treatment plants.