Microbial degradation of simulated landfill leachate: solid iron/sulfur interactions

Microcosms were prepared to test if added mineral Fe3+ and SO42- could trea t landfill leachate and to examine intrinsic microbial/mineral interactions related to natural attenuation. Two oxidized native sediments were used fr om central Oklahoma. Three types of anoxic microcosms were prepared which i ncluded the addition of: (1) mineral ferrihydrite (Fe(OH)(3)); (2) mineral gypsum (CaSO(4)(.)2H(2)O); and (3) no mineral amendments. Each received a s ynthetic leachate consisting of 2000 mg/I non-purgable organic carbon (NPOC ). Measurements of substrate consumption, dissolved ions, mineral utilizati on/precipitation, and biological gases were made over 12 weeks. The added C aSO42- and Fe(OH)(3) were used as electron accepters: CaSO42- by first orde r kinetics (k congruent to 0.12 week(-1)) and Fe3+ by zero order kinetics ( k congruent to 0.16 mM week(-1)). The addition of neither CaSO42- or Fe(OH) (3) did not increase organic carbon degradation rates over methanogenesis, which was predominate in the non-amended microcosm set. Adding solid electr on accepters promoted carbonate and sulfide mineral formation and controlle d greenhouse gases including CH4 and CO2. It is suggested that reduced Fe a nd S minerals could be used to assess organic contaminant degradation occur ring due to Fe3+ and SO42- microbial reduction processes for natural attenu ation studies. (C) 2001 Elsevier Science Ltd. All rights reserved.