Light intensity effect on the performance of Rhodobacter capsulatus in removal of chromium from effluent

The research aims to evaluate an unusual photosystem removing hexavalent chromium and total chromium contamination from the effluent by bioremediation (Rhodobacter capsulatus). Biomass and pigments (bacteriochlorophyll and carotenoid) production through different light intensities (dark, 800 lx, 3,200 lx, 5,670 lx, and 8,000 lx) were verified. The cultures were inoculated in 250 mL Erlenmeyer and operated under anaerobic conditions for 192 h. RCV medium with hexavalent chromium (10 mg/L, 30 mg/L, 60 mg/L, 90 mg/L, and 110 mg/L) was used. The findings show there was complete removal of hexavalent chromium. The increase in light intensity reduced the time for removal. Concerning total chromium, maximum removal occurred under 5,670 lx at low initial concentrations of hexavalent chromium of 10 mg/L (80.2 %), 30 mg/L (89.3 %), and 60 mg/L (77.0 %). Furthermore, the increase in light intensity up to 5,670 lx favored cell growth and pigment production. At 5,670 lx, there was a 230 % increase in biomass content in the culture with an initial concentration of 60 mg/L of hexavalent chromium. The final pigment contents were 2.22 mg/m3 (bacteriochlorophyll) and 1.44 mg/m3 (carotenoid).