Bio-remediation of pendimethalin contaminated soil by bio-slurry phase reactor: bio-augmenting with ETP micro-flora

Bio-remediation of pendimethalin contaminated soil (500 mu g/g) was studied in a bio-slurry phase reactor operated in the sequencing batch mode under anoxic-aerobic-anoxic micro-environment. The effect of augmentation with ETP micro-flora on the process performance of the reactor was also evaluated. The reactor was operated with a total cycle period of 120 hours comprising 3 hours of fill, 114 hours of react and 3 hours of decant phases. The Control reactor (without ETP micro-flora) showed 23% of substrate removal efficiency, which may be attributed to the volatile nature of the substrate. The Reactor operated with native soil micro-flora showed more or less equal degradation compared to the control reactor indicating the toxic and inhibitory nature of the substrate over the slurry micro-flora. The reactor augmented with mixed ETP micro-flora showed enhanced performance with more than 90% of substrate removal efficiency within 72 hours of the cycle period. Due to augmentation, the CFU values in the slurry phase system showed a two-fold increase. Process performance during reactor operation was assessed by monitoring pendimethalin concentration and bio-chemical process parameters viz. pH, dissolved oxygen (DO), colony forming units (CFU) and oxygen consumption rate (OCR), during sequence phase operation.