NOVELTY - System comprises: an inert substratum effective to adsorb hydrophobic persistent organic pollutants (POPs); and a biofilm on the substratum, where the biofilm comprises an active inoculum.    USE - The System is useful: for at least partially reducing or treating persistent organic pollutants (POPs), preferably polychlorinated biphenyls (PCBs) from the environment which is soil or sediment in-situ in closed or confined system (aquaculture system) (all claimed) via bioaugmentation.    ADVANTAGE - The system utilizing biofilm: exhibits faster microbial degradation of POPs, while simultaneously adsorbing hydrophobic POPs from the environment, thus making bioavailable for microorganisms and additionally lowering the aqueous concentration of POPs that have detrimental effects towards fish and mammals: selectively reduces any POP with low aqueous solubility; provides larger cell density in liquid cultures, thus exhibiting effective bioaugmentation; provides reductive dechlorination of low levels (1-2 ppm) of weathered PCBs even in the presence of high organic carbon: does not interfere with bioavailability of POPs, thus effective to treat low levels of POP; provides inoculum with sustained activity thus effective throughout the dechlorination process of PCBs and positive synergistic effect on dehalorespiring population; has high affinity for POP degrading biofilm forming bacteria and POPs; and provides two-phased approach in the methods leading to cost effective.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) making the system comprising formation of the biofilm on substratum;    (2) treating the POP-containing environment comprising administration of the system to the POP-containing environment;    (3) reducing POPs in a locus containing same, comprising introducing the biofilm comprising active inoculum supported on a hydrophobic surface to the locus; and    (4) bioaugmenting an aerobic dechlorination system comprising administration of the anaerobic dechlorination system having the substratum; and the biofilm.