P. N. Sarma

Microbial Electrolysis of Synthetic Acids for Biohydrogen Production: Influence of Biocatalyst Pretreatment and pH with the Function of Applied Potential

Bioelectrolysis of synthetic acids (acetate, butyrate and propionate) was evaluated in a single chamber Microbial Electrolysis Cell (MEC) to produce biohydrogen (H2). The influence of culture pretreatment (untreated and acid pretreated) and pH (6 and 7) conditions on electrolytic process were studied. MEC was operated at three optimized potentials viz., 0.2, 0.6 and 1.0 V along with control operated without any applied potential. Maximum Hydrogen Production Rate (HPR), Cumulative Hydrogen Production (CHP) and Specific Hydrogen Yield (SHY) were registered at 0.6 V followed by 1.0 and 0.2 V operations under all the experimental conditions studied. Culture pretreatment and pH variation showed influence on the MEC process. Pretreatment (PTr) operation at pH 7 showed good process performance than pH 6. MEC with untreated (UTr) at pH 6 and 7 showed lower performance compared to PTr operations. About 53% removal of synthetic acids was registered during the process which is a good sign for MEC as a wastewater treatment unit. Electrokinetic evaluation through Tafel slope showed that MEC operations with PTr and UTr at pH 6 recorded lower redox slopes and lower polarization resistance (Rp) at 0.2 V and 0.6 V whereas pH 7 recorded lower redox slopes and Rp at 0.6 V and 1.0 V.

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

Bio-remediation of pendimethalin contaminated soil (500 µg/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.