Treatment of sulphide containing wastewater with sulphur recovery in a novel reverse fluidized loop reactor (RFLR)

A novel aerobic bioreactor, the reverse fluidized loop reactor (RFLR) was tested for recovering sulphur from aqueous sulphide in this study. The RFLR contained buoyant carrier particles on which chemolithotrophic sulphide oxidizing bacteria formed a biofilm, which oxidized sulphide to sulphur and separated from the aqueous phase. The redox potential of the RFLR was regulated to control the oxygenation of sulphide for sulphur production. The RFLR was operated without any pH control and under various controlled pHs. The sulphide removal and nature of products formed under various sulphide loading rates and pH were examined. Under pH uncontrolled state, 95% of sulphur was recovered up to 11 kg sulphide/m3 d. The maximum sulphide loading supplied to the reactor was 30 kg sulphide/m3 d at pH 8, of which 90% was completely oxidized and 65% recovered as sulphur. The decline in bacterial sulphide oxidation leads to chemical oxidation of sulphide and subsequent accumulation of intermediary products such as thiosulphate and polysulphide in the reactor.