Anaerobic sulphide removal by haloalkaline sulphide oxidising bacteria

Sulphide is a toxic and corrosive compound and requires removal from waste streams. Recent discoveries show that sulphide oxidising bacteria (SOB) from modern desulphurisation plants are able to spatially separate sulphide removal and oxygen reduction when exposed to intermittent anaerobic and aerobic environments. Here, SOB act as electron shuttles between electron donor and acceptor. The underlying mechanisms for electron shuttling are of yet unknown. To investigate the anaerobic sulphide removal of SOB, batch experiments and mathematical models were applied. The sulphide removal capacity decreased at increasing biomass concentrations. At 0.6 mgN/L SOB could remove up to 8 mgS/mgN in 30 min. It was found that biological activity determines sulphide removal, alongside chemical processes. Anaerobic oxidation of electron carriers was determined to only explain 0.1% of charge storage, where irreversible cleavage of long chain polysulphides could explain full sulphide storage. Different sulphide removal and intracellular storage processes are postulated.