Introduction of a de novo bioremediation ability, aryl reductive dechlorination, into anaerobic granular sludge by inoculation of sludge with Desulfomonile tiedjei

Methanogenic upflow anaerobic granular-sludge blanket (UASB) reactors treat wastewaters at a high rate while simultaneously producing a useful product, methane; however, recalcitrant environmental pollutants may not be degraded. To impart 3-chlorobenzoate (3-CB)-dechlorinating ability to UASB reactors, we inoculated granular sludge in UASB reactors with either a pure culture of Desulfomonile tiedjei (a 3-CB-dechlorinating anaerobe) or a three-member consortium consisting of D. tiejei, a benzoate degrader, and an H2-utilizing methanogen. No degradation occurred in an uninoculated control reactor which was started with the same granular sludge, but inoculated reactors and granules from the inoculated UASB systems rapidly transformed 3-CB (54 mumol/day/g of granule biomass). After several months at a hydraulic retention time of 0.5 day, much shorter than the generation time of D. tiedjei, the reactors still dechlorinated 3-CB. This indicated that the bacteria were immobilized in the reactor granules, and by using an antibody probe for D. tiedjei, we demonstrated that this microorganism had colonized the sludge granules. These results represent the first addition of a pure culture or a defined microbial mixture to a viable waste treatment process to introduce a specific de novo degradative pathway into a granular-sludge consortium.