Biological desulfurization in an optical-fiber photobioreactor using an automatic sunlight collection system

Biological desulfurization using C. thiosulfatophilum has many more advanta ges over conventional physico-chemical methods due to low operational cost and no production of secondary pollutants. However, it requires effective a nd economical supply of light energy, which is a key factor in determining the success of commercialization. In this study, optical-fiber photobioreac tor with internal illumination system was applied to increase the light ava ilability. Furthermore, sunlight was used as the main light energy in the d aytime and metal-halide lamp was applied as an additional light energy at n ight. Most UV light was eliminated by the chromatic aberration of the asphe rical lenses in the solar light collector and 60% of infrared light intensi ty was eliminated. Physical scratching optical fibers enhanced the light av ailability about five times as much as that with unscratched ones in the pr evious study, but it resulted in the adsorption problem of elementary sulfu r particles deteriorating light diffusivity considerably in a long operatio n. In order to solve this problem, scratched optical fibers were inserted i nto pyrex-glass tubes, which made light diffusivity nearly the same as that without glass tubes. Removal rate per unit cell concentration, using sunli ght in the daytime and a metal-halide lamp at night, was 0.41 < 0.73 mu mol H2S min(-1)/(mg protein l(-1)) using a 400 W metal-halide lamp day and nig ht, since the automatic sunlight collection system can transmit the light i ntensity as only 10% of that with a metal-halide lamp. (C) 2000 Elsevier Sc ience B.V. All rights reserved.