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 e lemental sulphur in a fixed-film continuous-flow photosynthetic bioreactor. Twenty 150 min x 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. S ulphide loading rates ranged from I I I to 328 mg/h L under influent flowra tes of 9.0-42.4 mL/h and hydraulic retention times of 0.50 2.35h. The irrad iance at the reactor surface averaged 25.4 W/m(2), The sulphide removal rat es 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 b e 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 p er unit reactor volume and the bacteriochlorophyll concentration as express ed by the van Niel curve. (C) 2001 Elsevier Science Ltd. All rights reserve d.