Copper effect in sulfate removal using a fixed bed reactor

Abstract

Mining of sulfide-rich pyritic ores produce acid mine drainage (AMD), which contains high metal concentrations and have acid pH, causing major environmental problems. Over the last 20 years a variety of passive AMD treatment systems, like anaerobic wetlands, bioreactors and permeable reactive barriers, have been studied. Under controlled conditions bioreactors employ inoculants of sulfate-reducing bacteria (SRB) to treat effluents and capture commercial grade metals. The objective of this research was to evaluate the effect of Cu on the removal efficiency of sulfate in a fixed bed reactor. During 28 d the fixed bed reactor maintained a hydraulic residence time (HRT) of 12 h and an influent rate of 0.67 gCOD/gSO42–. Phase I (synthetic solution with 50 mg Cu/L) lasted 7 d, allowing Cu removal of 99.59 ± 0.43 % and sulfide production of 39.29 mg S2-/L∙d. Sulfate-reducing activity (SRA) was not affected (40.25 mg S2-/L∙d) during Phase II (21 d without Cu). Results showed no significant alteration in sulfate and COD removal, as well as sulfur production after the addition of Cu. It is concluded that SRB can be used for AMD treatment.