ORIGINAL ARTICLE The status of the passive treatment systems for acid mine drainage in South Korea Sangwoo Ji Æ Sunjoon Kim Æ Juin Ko Received: 18 July 2007 / Accepted: 1 October 2007 / Published online: 17 October 2007 Ó Springer-Verlag 2007 Abstract This study was performed to investigate the operating status, evaluate the problems, and discuss pos- sible improvement methods of passive treatment systems for acid mine drainage (AMD) in South Korea. Thirty-five passive treatment systems in 29 mines have been con- structed from 1996 to 2002 using successive alkalinity producing systems (SAPS) as the main treatment process. We investigated 29 systems (two for metal mines), 19 of which revealed various problems. Overflows of drainage from SAPS, wetland, or oxidation ponds were caused by the flow rate exceeding the capacities of the facilities or by the reduced permeability of the organic substance layer. Leakages occurred at various parts of the systems. In some cases, clogged and broken pipes at the mouths of the mine adits made the whole system unusable. Some systems showed very low efficiencies without apparent leakage or overflow. Even though the systems showed fairly good efficiencies in metal removal ratios (mainly iron) and pH control; sulfate removal rates were very poor except in three systems, which may indicate very poor sulfate reductions with sulfate reducing bacteria (SRB) as a means. Keywords Acid mine drainage (AMD)  Successive alkalinity producing systems (SAPS)  Sulfate reducing bacteria (SRB) Introduction Acid mine drainage (AMD) is a major environmental hazard that affects the aquatic ecosystems around mines. In coal-mining areas, the most common of these minerals is pyrite (FeS 2 ). The process for AMD formation is com- monly represented by the following reactions: FeS 2 ðsÞþ 3:5O 2 þ H 2 O ! Fe 2þ þ 2SO 2 4 þ H þ ð1Þ Fe 2þ þ 0:25O 2 þ H þ ! Fe 3þ þ 0:5H 2 O ð2Þ Fe 3þ þ 3H 2 O ! Fe(OH) 3 ðsÞþ 3H þ ð3Þ The process is initiated with the oxidation of pyrite and the release of ferrous iron (Fe 2+ ), sulfate, and acidity (Eq. 1). The sulfide-oxidation process is accelerated by the pres- ence of Thiobacillus bacteria. Ferrous iron then undergoes oxidation, forming ferric iron (Fe 3+ ) (Eq. 2). Finally, Fe 3+ reacts with H 2 O (is hydrolyzed), forming insoluble ferric hydroxide (Fe(OH) 3 ), an orange-colored precipitate, that releases additional acidity (Eq. 3). The Fe(OH) 3 formation process is pH-dependent, and occurs rapidly when pH [ 4 (Stumm and Morgan 1996). In 1996, the CIPB (Coal Industry Promotion Board) estimated that about 153 km of streams were impacted by AMD of 48,000 tons/day from 152 coal mines (CIPB 2000). Since 1989, over 98% of coal mines in Korea have been closed by the coal industry promotion program and only nine coal mines are still in operation. Also more than S. Ji The Environmental Hazardous Group, The Korea Institute of Geoscience and Mineral Resources (KIGAM), 30 Gajeong-dong, Yuseong-gu, Daejeon 305-350, South Korea e-mail: swji@kigam.re.kr S. Kim (&)  J. Ko Department of Geoenvirenmental System Engineering, Hanyang University, 17, Handang-dong, Seongdong-gu, Seoul 133-791, South Korea e-mail: nnsjkim@hanyang.ac.kr J. Ko e-mail: kojuin74@hanmail.net 123 Environ Geol (2008) 55:1181–1194 DOI 10.1007/s00254-007-1064-4