Demonstration of simultaneous biological sulphate reduction and partial sulphide oxidation in a hybrid linear flow channel reactor

Abstract Semi-passive remediation systems have the potential to treat low-volume, sulphate-rich, mining impacted waters in a sustainable way. This paper describes the “proof of concept” evaluation of a hybrid linear flow channel reactor, capable of efficient biological sulphate reduction and partial oxidation of the sulphide to elemental sulphur. Key elements include a sulphate-reducing microbial community, immobilised onto carbon fibres and the rapid development of a floating sulphur biofilm at the air-liquid interface. The biofilm impedes oxygen mass transfer, creating a suitable pH-redox microenvironment for partial sulphide oxidation. Demonstration of the concept was successful, with near complete sulphate reduction (1 g/L feed), effective sulphide management (95–100 % removal) and partial recovery of sulphur by harvesting the biofilm. The biofilm re-formed within 24 h, with no decrease in volumetric sulphate reduction rate during this period. Colonisation of the carbon microfibers ensured biomass retention, suggesting the reactor could remain effective at high volumetric flow rates.