Biological conversion of hydrogen sulphide to elemental sulphur in a fixed-film continuous flow photo-reactor

The green sulphur bacterium Chlorobium thiosulfatophilum was used to remove hydrogen sulphide from synthetic industrial wastewater and convert it to elemental sulphur in a fixed-film continuous-flow photosynthetic bioreactor. Twenty 150 mm×3 mm ID Tygon tubes formed the active part of the reactor resulting in a total volume of 21.2 mL. Seven steady states were achieved under different experimental conditions using this tubular photo-reactor. Sulphide loading rates ranged from 111 to 328 mg/h L under influent flowrates of 9.0–42.4 mL/h and hydraulic retention times of 0.50–2.35 h. The irradiance at the reactor surface averaged 25.4 W/m2. The sulphide removal rates were found to be 82–100 % and elemental sulphur recovery rates were found to be 75–95%. The maximum sustainable sulphide loading rate was found to be 286 mg/h L, which is 2.5 times higher than the previous reported highest value. Sulphide loading rate was found to be the function of radiant flux per unit reactor volume and the bacteriochlorophyll concentration as expressed by the van Niel curve.