Attenuation of acid rock drainage by stimulating sulfur-reducing bacteria

Abstract Iron-sulfide minerals found in shale formations are stable under anaerobic conditions. However, the presence of oxygen and water, acid-loving chemolithotrophic bacteria can transform iron-sulfide into a toxic solution sulfuric acid dissolved iron known as rock drainage (ARD). The objective this study was to disrupt responsible for ARD using chemical treatments foster an environment favorable competing microorganisms attenuate biologically induced ARD. Chemical were injected flow-through microcosms consisting 501 g pyrite-rich pieces inoculated with bacteria. Three tested microcosms: (1) sodium hydroxide-bleach mix, (2) lactate solution, (3) lactate-soy infant formula mix. effectiveness assessed by monitoring pH, iron, other geochemical constituents discharge waters. optimal treatment sequential injection 1.5 hydroxide, followed 0.75 soy 20 mL water. pH water rose 6.0 within 10 days, concentrations dropped below 1 mg/L, median alkalinity increased 98 mg/L CaCO 3 , sulfur-reducing slime-producing populations stimulated. attenuating benefits still evident after 231 days. Other provided number effects but tempered problems such high phosphate concentrations, short longevity, or shortcomings. results these laboratory microcosm experiments promising attenuation Additional investigations careful selection methods will be needed field application.