Ž . Advances in Environmental Research 5 2001 103116 Microbial degradation of simulated landfill leachate: solid ironsulfur interactions Lonnie G. Kennedy a,  , Jess W. Everett b a Earth Science Ser  ices, 5815 Hickory Bend, Norman, OK 73026, USA b Department of Ci  il Engineering, Rowan Uni  ersity, 201 Mullica Hill Rd., Glassboro, NJ 08028, USA Accepted 24 August 2000 Abstract Microcosms were prepared to test if added mineral Fe 3 and SO 2 could treat landfill leachate and to examine 4 intrinsic microbialmineral interactions related to natural attenuation. Two oxidized native sediments were used Ž. from central Oklahoma. Three types of anoxic microcosms were prepared which included the addition of: 1 mineral Ž Ž .. Ž. Ž  . Ž. ferrihydrite Fe OH ; 2 mineral gypsum CaSO 2H O ; and 3 no mineral amendments. Each received a 3 4 2 Ž . synthetic leachate consisting of 2000 mgl non-purgable organic carbon NPOC . Measurements of substrate consumption, dissolved ions, mineral utilizationprecipitation, and biological gases were made over 12 weeks. The 2 Ž . 2 Ž 1 . added CaSO and Fe OH were used as electron acceptors: CaSO by first order kinetics k 0.12 week and 4 3 4 3 Ž 1 . 2 Ž . Fe by zero order kinetics k 0.16 mM week . The addition of either CaSO or Fe OH did not increase 4 3 organic carbon degradation rates over methanogenesis, which was predominate in the non-amended microcosm set. Adding solid electron acceptors promoted carbonate and sulfide mineral formation and controlled greenhouse gases including CH and CO . It is suggested that reduced Fe and S minerals could be used to assess organic contaminant 4 2 degradation occurring due to Fe 3 and SO 2 microbial reduction processes for natural attenuation studies.  2001 4 Elsevier Science Ltd. All rights reserved. Keywords: Iron reduction; Sulfate reduction; Methanogenesis; Intrinsic bioremediation; Natural attenuation; Landfill leachate; Remediation 1. Introduction 1.1. Purpose Excluding closed landfills, there are approximately 3000 active municipal solid waste landfills in use in the Ž . United States alone Goldstein, 1997 . Some of these landfills, particularly the older, unlined ones, have re-  Corresponding author. Tel.: 1-405-364-6431. Ž . E-mail address: lkennedy@telepath.com L.G. Kennedy . leased leachate to soilground water while green house gases can be emitted to the atmosphere. Modern land- fills contain systems for leachate collection; however, this leachate often requires supplemental treatment. In addition to inorganic salts and dissolved metal contami- nants, landfill leachate is typically high in organic con- stituents, with measured COD values ranging from Ž 7750 to 60 000 mgl Baedecker and Back, 1979; Hoeks . and Borst, 1982; Kjeldsen and Christensen, 1994 . Es- caped leachate is a source of soil, ground water, and occasionally surface water pollution that may persist Ž . for many decades Belevi and Baccini, 1992 . Landfill 1093-019101$ - see front matter  2001 Elsevier Science Ltd. All rights reserved. Ž . PII: S 1 0 9 3 - 0 1 9 1 00 00047-2