Abstract
Biological sulphate reduction and partial sulphide oxidation, occurring simultaneously within the hybrid linear flow channel reactor (LFCR) were evaluated, under controlled conditions at laboratory scale, as a function of hydraulic residence time (HRT) using a synthetic media containing 1 g/L sulphate. The hybrid LFCR comprises a rectangular channel containing carbon microfibers as a support matrix for attachment of sulphate-reducing bacteria and an exposed air-liquid interface to facilitate the formation of a floating sulphur biofilm. Exposure to decreasing HRT, from 3 days to 12 h, resulted in an increase in the volumetric sulphate reduction rate (0.14 to 0.63 mmol/L.h), achieving levels typically associated with active reactors. Sulphate conversion was highest (97 %) at a 3 day HRT, decreasing to 73 % at 12 h. The highest sulphide removal efficiency (82 %) and accompanying sulphur recovery through harvesting of the floating sulphur biofilm (FSB) was observed at a 2 day HRT. The sulphur fraction not recovered through the biofilm was predominantly released within the effluent as colloidal elemental sulphur and fragments of the sulphur-rich biofilm, with minimal re-oxidation to sulphate occurring in the reactor. The hybrid LFCR technology was able to achieve high rates of sulphate reduction and effective sulphide removal within a single, semi-passive reactor unit.
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