The research aimed to investigate the sustainability of the dechlorination ability of the microbes after long-term cold storage. Polychlorinated biphenyls (PCBs) dechlorinating bacteria were activated and characterised
by priming congeners. Sediment slurries (SS) were collected from several streams around the Samut Prakan Province in Thailand. While dechlorination of 234-CBp was persistent, 2345-CBp dechlorination was relatively more active. Halogenated priming congeners, including methyl 4-bromobenzene, 14-dibromobenzene, 4-bromobenzonitrile, and 4-bromobezoic hydrazide, could significantly stimulate the dechlorination of 234-CBp but not 2345- CBp. The identified PCB dechlorinating groups were Firmicutes and Proteobacteria. Halogenated priming congeners could activate dechlorination in Thailand, where PCBs dechlorinating microbes were abundant.