Studies on the biodegradation of some chlorophenolics in secondary sludge of pulp and paper industry

Abstract

Twelve different bacteria (CL1 to CL12) were isolated from the sludge by enrichment technique using chlorophenol as sole source of carbon and energy. Five isolates CL2, CL3, CL5, CL7 and CL11 were used Pentachlorophenol (PCP) as sole source of carbon and energy and degraded up to 90% at 600 mg/l. These isolates have shown maximum degradation of PCP within pH range of 7.5 to 8.5 and temperature 37and#61616;C. All the isolate utilizes 2,3,4,6-Tetrachlorophenol (TeCP) up to 600 mg/l and degraded up to 90% except two isolates CL7 and CL8 having slightly less degradation ability which was up to 75 to 80%. Maximum TeCP removed at pH 8.5 and temperature 37and#61616;C. Five isolates CL2, CL5, CL7, CL9 and CL10 utilized 2,4,5-trichlorophenol (2,4,5-TCP). CL2, CL5 and CL9 removed 2,4,5-TCP 90% at 600 mg/l where as CL7 and CL10 removed 85%. All these isolates removed maximum at pH 7.5 and temperature 37and#61616;C. CL4, CL5, CL7, CL9 and CL11 isolates were screened for the degradation of 2,4,6-TCP as sole carbon and energy sources. All these five isolates were able to remove 2,4,6-TCP by more than 90% at 600 mg/l except CL7 which removed up to 85%. Most favorable pH for the removal of 2,4,6-TCP was 7.5 by these isolates. All these isolates have maximum degradation potential at 37and#61616;C. The remediation of chlorophenols (PCP, TeCP, 2,4,5-TCP, 2,4,6-TCP) in the secondary sludge was assessed by adding the mixed inocolum or consortium into the sludge separately at pilot scale. Consortium of the isolates for a particular chlorophenol removed 100% of PCP, TeCP, 2,4,5-TCP , 2,4,6-TCP up to 100 mg/l from the sludge within two weeks period. Further all these isolates were morphologically, biochemically and molecularly (based on 16s rRNA gene analysis) characterized. Result found that most of the isolates belong to phylum Fermicutes, two isolates CL2 and CL6 belongs to phylum Actinobacteria and one isolates CL7 belongs to Proteobacteria.