Introduction of Bioremediation Ability into Granular Sludge

Abstract

Three 200 ml upflow anaerobic sludge blanket (UASB)-reactors were inoculated with sugar degrading granules. To impart 3-chlorobenzoate degrading ability to the reactors, one was inoculated with the 3-chlorobenzoate (3-CB) dechlorinating Desulfomonile tiedjei, and the second received a 3-CB dechlorinating consortium, consisting of D.tiedjei and a benzoate degrading coculture of Syntrophus buswellii with Methanospirillum sp. No degradation of 3-CB was observed in the third reactor only inoculated with granules. After several months operation at a hydraulic retention time at 0.5 day, shorter than the reported generation time of D. tiedjei, the reactors showed increasing dechlorinating abilities. Activity tests done with granules from the control and the consortium-inoculated reactor showed no activity in the control reactor and no significant difference in the specific dechlorination rate with granules from the top, middle or bottom layer of the active reactor sludge bed, with or without carbon source added. This indicated that the added bacteria were immobilized in the granules and they were responsible for the dechlorinating activity. These results have important implications for the use of pure anaerobic culture or defined microbial mixtures in viable waste treatment processes.