INTRODUCTION OF A DE-NOVO BIOREMEDIATION ACTIVITY INTO ANAEROBIC GRANULAR SLUDGE USING THE DECHLORINATING BACTERIUM DCB-2

The strictly anaerobic, pentachlorophenol (PCP) degrading bacterium DC B-2 was immobilized in an Upflow Anaerobic Sludge Blanket (UASB) react or containing sterile granules. PCP and lactate were fed to the reacto r and the concentration of chlorophenols in the effluent were monitore d for 641 days. PCP was found to be degraded and transformed into 3.4. 5-trichlorophenol in the reactor where DCB-2 was introduced into the g ranular sludge. PCP was still transformed to 3.4.5-trichlorophenol whe n the hydraulic retention time was decreased to six hours which was mu ch lower than the generation time of DCB-2 insuring no free living cel ls in the reactor. This indicated that DCB-2 was immobilized in the gr anular layer. A control reactor that contained only sterile granules d id not dechlorinate PCP indicating that the performance in the inocula ted reactor was only due to the introduced bacteria. Immobilization of DCB-2 in the granules was further demonstrated by adding an antibody raised against DCB-2 to sliced granules. Bacteria thus visualized form ed a net structure inside the granules. No DCB-2 bacteria could be fou nd in granules from the control reactor. When lactate was omitted from the influent, the reactor still dechlorinated PCP in accordance with our findings that lactate;was not used by DCB-2. This suggested that t he reducing equivalents for reductive dechlorination were derived from the granules themselves. The reactor performance was 120 mu mol . l r eactor(-1). day(-1), comparable to the best described performance of a UASB-reactor and to aerobic reactors. Our study demonstrates that gra nules can be constructed which possess specific abilities such as a de chlorinating activity and at the same time be high performing. This re sult have implications for eco-engineering of granules for anaerobic t reatment of contaminated waters.