Moving Bed Biofilm Reactor for Selenium Removal from FGD and Mine Effluents

Biological selenium removal was studied in laboratory models of MBBR`s treating authentic wastewaters. The MBBR-effluents were treated with coagulation and flocculation for solids removal. Glucose or Micro C was added as carbon sources. Results from treatment of an FGD effluent from a power plant in a two-stage MBBR at 30°C showed that total selenium could be reduced from 250 ppb to 10-20 ppb. The feed also contained 90 ppm of NO3-N which was reduced to below 0.2 ppm in the process. Treatment of a mine effluent in a two-stage MBBR at temperatures down to 6° C reduced the selenium from 38 ppb to 3-5 ppb. NO3-N was reduced from 23 to below 0.2 ppm across the process. Another mine effluent with significantly higher concentration of total selenium, 560 ppb, but relatively low NO3-N, 1.5 ppm, was treated at temperatures down to 10°C in a two-stage MBBR. Total selenium was reduced to 6-20 ppb. The results demonstrate that MBBR can be a viable option for removal of selenium and nitrate from both FGD and mine effluents. The development is ongoing to optimize the MBBR design as well as the post-treatment.