Three reactor systems were compared in order to assess their suitability for a new biotechnological sulphide removal process. This process is based on the conversion of sulphide to sulphur. The sulphide removal rates under conditions where the sulphide effluent concentration did not exceed 2 mg/l was for the CSTR (completely mixed tank reactor), biorotor and upflow reactors 2.4, 10, 11 kg-S/m3· day, respectively. The differences in volumetric sulphide load in these cases mainly depend on the different sludge concentrations. When using Rasschig rings (rings with a cylindrical shape, diameter of 5 cm, height of 3 cm and total surface of 180 cm2) instead of PUR (recticulated polyurethane) particles the capacity for the biorotor system decreased to 5.0 kg-S/m3· day. The applicable hydraulic retention times at a sulphide influent concentration of 100 mg/l for sulphide effluent concentrations below 2 mg/l were for the CSTR, biorotor and upflow reactors 35, 10 and 13 min, respectively. Under identical operational conditions the sulphate prodution in the biorotor and upstream reactors remains lower than in the CSTR. The sulphate production rate in the biorotor can be controlled by changing the oxygen concentration in the gasphase and in the other two reactor systems by changing the dissolved oxygen concentration. © 1990.
