More rapid dechlorination of 2,4-dichlorophenol using acclimated bacteria

[Display omitted] •Removal of Cl at the para position was key for mineralization of 2,4-DCP.•Bacteria acclimated to 4-CP could rapidly remove Cl at the para position.•Augmenting with 4-CP-dechlorinating bacteria allowed mineralization of 2,4-DCP.•Treponema, Dechloromonas, and Thauera were involved in dechlorinating 2,4-DCP.•Nitrospira and Blvii28 also may play roles in removal of Cl at the para-position. The key step for anaerobic biodegradation of 2,4-dichlorophenol (2,4-DCP) is an initial dechlorination reaction, but Cl in the para-position is more difficult to remove than Cl in the ortho-position using normal 2,4-DCP-acclimated bacteria. In this work, a bacterial community previously acclimated to biodegrading 2,4-DCP slowly dechlorinated 4-chlorophenol (4-CP Cl only in the para-position), which limited mineralization. That community was exposed to the selective pressure of having 4-CP as its only organic substrate in order to generate a 4-CP-dechlorinating community. When the 4-CP-dechlorinating community was challenged with 2,4-DCP, 4-CP hardly accumulated, although the kinetics for 2,4-DCP biodegradation were slower. When the community acclimated to 4-CP was mixed with the community acclimated to 2,4-DCP, the 2,4-DCP removal rate remained high, and 4-CP was more rapidly biodegraded. The genera Treponema, Blvii28, Dechloromonas, Nitrospira, and Thauera were significantly more abundant in the 4-CP-dechlorinating biomass and may have played roles in 2,4-DCP dechlorination and mineralization.