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

The green sulphur bacterium Chlorobium thiosulfutophilum 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 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. Sulphide loading rates ranged from 111 to 328 mg/hL 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.

Extraction of elemental sulfur from an aqueous suspension for analysis by high-performance liquid chromatography.

A bioreactor is being developed that produces elemental sulfur suspended in aqueous bioreactor contents. The concentration of elemental sulfur must be measured explicitly in order to study the efficiency of the conversion of sulfide to elemental sulfur. Extracting the sample with ethanol gave erroneous results when sulfide was present in solution. The extraction of aqueous elemental sulfur into petroleum ether prior to colorimetric determination was tested. When the aqueous matrix was simply deionized water, the extraction was poor. The development of a method of extraction of the sulfur into chloroform prior to quantification by high-performance liquid chromatography is described. The efficiency of the extraction was found to be greater than 90% in all matrixes tested and linear for aqueous elemental sulfur concentrations up to 200 mg/L.