Bioaugmentation of a soil bioreactor designed for pilot-scale anaerobic bioremediation studies

The aim of this work was to answer the following questions: (i) Can we real ize a long-term dechlorination with a pure anaerobic strain in soil and (ii ) can we monitor the process on an adequate scale with a controlled simulat or of in situ conditions (soil bioreactor of a 500-L scale). The soil biore actor was fed continuously with 3-chlorobenzoate (3-CB) as a model chloroar omatic compound. Bioaugmentation was carried out by inoculating Desulfomoni le tiedjei in localized areas in the bioreactor. Temporal and spatial distr ibution of the 3-CB dechlorination activity was investigated with specific biological activity tests for approximately 4 months following the inoculat ion. These tests involved the minimally invasive sampling of geometrically distinct points in the reactor and their off-site handling within reconstru cted microcosms, allowing the assessment of dechlorinating and methanogenic soil activities. Using autoclaved and nonautoclaved agricultural soil, the results showed a heterogeneous distribution of the dechlorination activity in the bioreactor. The autoclaved soil expressed a high microbial activity as reflected by biogas production and 3-CB dechlorination. Furthermore, du rable establishment of D, tiedjei in both autoclaved and nonautoclaved soil was shown, although in the latter portion of the reactor the microorganism was maintained only at the top surface. Polymerase chain reaction (PCR) de tection of the 16S rDNA gene of D. tiedjei was directly correlated with 3-C B dechlorination activity. Denaturing gradient gel electrophoresis (DGGE) a nalysis of PCR products demonstrated distinct bacterial community fingerpri nts in soil samples as a function of location and in response to process mo difications. This investigation demonstrates for the first time the applica bility and limitations of soil bioaugmentation with a pure anaerobic dechlo rinating strain at a realistic pilot scare.