Degradation of 2,4,6-trichlorophenol by bacteria isolated from secondary sludge of a pulp and paper mill

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Bacterial strains capable of degrading trichlorophenol (2,4,6-TCP) were isolated from the secondary sludge of a pulp and paper mill and were characterized. These isolates were identified as Planococcus rifietoensis (CL4) and Bacillus pumilus (CL5), based on their 16S rRNA sequence analysis. These isolates were able to grow and utilize 2,4,6-TCP as their source of carbon as well as energy. HPLC analysis and stoichometric release of chloride in the medium confirmed the degradation ability of these isolates. Removal efficiency of 2,4,6-TCP by these isolates was discovered to be high. They were able to remove 90% of 2,4,6-TCP when grown at a concentration of 600 mg L⁻¹. Inoculation of these bacteria completely removed 2,4,6-TCP within 2 weeks from the sludge of the pulp and paper mill when supplemented at the rate of 100 mg L⁻¹. Absorbable Organic Halogen (AOX) and Extractable Organic Halogen (EOX) were significantly reduced by 63% and 70% respectively from the sludge due to inoculation of these bacteria. These isolates have high potential to remove 2,4,6-TCP and may be used for removal of 2,4,6-TCP from pulp paper mill waste.