Development of the floating sulphur biofilm reactor for sulphide oxidation in biological water treatment systems

The formation of floating sulphur biofilm was observed in the microbial ecology studies of tannery ponds undertaken by the Environmental Biotechnology Group at Rhodes University. This was related to the steep Redox gradients established at the air/ water interface of anaerobic, organically loaded and actively sulphate reducing systems. This study investigated the potential for applying these observations in developing a floating sulphur biofilm reactor for the removal of sulphide from sulphide-rich effluents produced in wastewater treatment systems. This was carried out in five sequential experimental phases. Where original studies had been undertaken using sulphide-rich water derived from sewage sludge as the carbon source, the successful establishment of a floating sulphur biofilm from effluent of lignocellulose-derived wastewaters had been shown. The effect of influent sulphide concentrations, flow rate and reactor dimensions on the sulphur biofilm formation were investigated for the optimisation of elemental sulphur recovery and sulphide removal efficiency. Polysulphide formation was enhanced by inserting a silicone tube rack and resulted in increased elemental sulphur recovery. Sulphide removal efficiency of 65% and a sulphur recovery of 85% were obtained at the end of the investigation while inter-harvest recovery period of the biofilm was reduced from an initial 4-5 days to 6-12 hours. Water SA Vol. 30 (5) 2005: pp.655-65