The Role of Bacteria on the Breakdown of Recalcitrant Polychlorinated Biphenyls (PCBs) Compounds in Wastewater

Abstract

Pseudomonas aeruginosa was used to assess their potentials to degrade PCBs at concentra- tions of 1.0 μ g/mL. An aliquot of 1.0 μ L of the bacterial suspension with an optical density of 1.0 at 600 nm was used as an inoculum of the assay. Isolates were analysed for their ability to degrade PCB (Aroclor 1260) by measuring a shift in the wavemax using Cary 300 UV-visible spectrophotometer for a period of 96 hours. The presence /absence of the compounds was checked using high performance liquid chromatography (HPLC) UFLC Shimadzu using florescence detector pump RF-20A and system gold column C18 (CTO- 20A) after 96 h. PCBs were extracted from wastewater samples from both Gaborone and Mafikeng using the Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) extrac- tion kit, and analysis was performed using the gas chromatography mass spectrometer (GC-MS). The bacteria were able to degrade these compounds under different pH values of 5.0, 7.0, 8.0, and 9.0 and temperatures of 20, 27, 30, and 35 (cid:1) C. Degradation occurred at the most at 35 (cid:1) C and the least at 20 (cid:1) C for PCB samples that were used in the study. The bacteria strain was able to completely degrade Aroclor 1260 that was incoperated into the wastewater samples within 96 h. This was shown by a shift in the wavelength from 224 to 270 nm, which indicated that Aroclor 1260 was degraded and therefore forming a chlorobenzoate derivative. From this finding, it can be concluded that the sewage water samples did not possess PCB (Aroclor 1260) after treatment with bacteria and can be safely recycled.