Search

Byline: M. Rama Krishna, S. Shailaja, K. Sirisha, S. Venkata Mohan, P.N. Sarma Bio-remediation of pendimethalin contaminated soil (500 [acute accent]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.

To study the bioelectrochemical behaviour of Pseudomonas aeruginosa (MTCC 17702) and Escherichia coli (MTCC 10436) and to assess their potential to act as anodic biocatalyst with the function of anaerobic consortia for microbial (bio) fuel cell (BFC) application. Three BFCs (single chamber; open-air cathode; noncatalysed electrodes) were operated simultaneously in acidophilic microenvironments. Pseudomonas aeruginosa (BFC) showed higher current density (264 mA m) followed by mixed culture (BFC; 166 mA m) and E. coli (BFC; 147 mA m). However, total operating period and substrate degradation were relatively found to be effective with mixed culture (58%; 72 h) followed by BFC (39%; 60 h) and BFC (31%; 48 h). Higher electron discharge (ED) was observed with Ps. aeruginosa while mixed culture showed the involvement of redox mediators in the ED process. Mixed culture showed to sustain biopotential for longer periods along with a stable ED. The presence of redox signals and high substrate degradation was also evidencing its performance compared to the pure strains studied. This supports the practical utility of mixed culture over the pure cultures for real-field BFC applications especially while operating with wastewater. This study revealed the efficiency and viability of mixed consortia in comparison with pure strains for microbial (bio) fuel cell applications. [ABSTRACT FROM AUTHOR]

Lactobacillus acidophilus was used for the removal of As(III) from 50-2000 ppb As(III)-containing water solution. Biosorption of As(III) by L. acidophilus was dependent on concentration (50 to 2000 ppb) and time (0 to 3 h).L. acidophilus(1 mg dry wt/ml) was able to remove 30, 60, 300, 420, 600 ppb As(III) from 50, 100, 500, 1000, and 2000 ppb of As(III)-containing water solution, respectively, within 3 h at pH 7. Moreover, by increasing the biomass of L. acidophilus(2 mg dry wt/ml) removal of As(III) was enhanced 1.66, 1.33, 1.16, 1.42, and 1.33 times, respectively. Fourier transform infrared (FTIR) and electron spectroscopy for chemical analysis (ESCA) spectrum of As(III)-loaded biomass was also investigated. An FTIR sample spectrum of L. acidophilus fresh biomass and As(III)-loaded biomass showed band stretching of fresh and As(III)-loaded biomass for O-H, 3423.43 to 3385.04 cm-1, and for C-O, 1742.82 to 1731.14 cm-1, and signified that -OH and -CO groups were also involved in the removal of As(III) from As(III)-containing water solution. [ABSTRACT FROM AUTHOR]

Design of experimental (DOE) methodology using Taguchi orthogonal array (OA) was applied to evaluate the influence of eight biotic and abiotic factors (substrate-loading rate, slurry phase pH, slurry phase dissolved oxygen (DO), soil water ratio, temperature, soil microflora load, application of bioaugmentation and humic substance concentration) on the soil bound chlorpyrifos bioremediation in bioslurry phase reactor. The selected eight factors were considered at three levels (18 experiments) in the experimental design. Substrate-loading rate showed significant influence on the bioremediation process among the selected factors. Derived optimum operating conditions obtained by the methodology showed enhanced chlorpyrifos degradation from 1479.99 to 2458.33μg/g (over all 39.82% enhancement). The proposed method facilitated systematic mathematical approach to understand the complex bioremediation process and the optimization of near optimum design parameters, only with a few well-defined experimental sets. [Copyright &y& Elsevier]

Abstract: Bio (microbial) fuel cell (microbial fuel cell) with Saccharomyces cerevisiae as anodic biocatalyst was evaluated in terms of power generation and substrate degradation at three redox conditions (5.0, 6.0 and 7.0). Fuel cell was operated in single chamber (open-air cathode) configuration without mediators using non-catalyzed graphite as electrodes. The performance was further studied with increasing loading rate (OLRI, 0.91kg COD/m3-day; OLRII, 1.43kg COD/m3). Higher current density was observed at pH6.0 [160.36mA/m2 (OLRI); 282.83mA/m2 (OLRII)] than pH5.0 (137.24mA/m2) and pH 7.0 (129.25mA/m2). Bio-electrochemical behavior of fuel cell was evaluated using cyclic voltammetry which showed the presence of redox mediators (NADH/NAD+; FADH/FAD+). Higher electron discharge was observed at pH6.0, suggesting higher proton shuttling through the involvement of different redox mediators. The application of yeast based fuel cell can be extended to treat high strength wastewaters with simultaneous power generation. [ABSTRACT FROM AUTHOR]

Abstract: Positive influence of poised potential on microbial fuel cell (MFC) performance was observed with increase in the applied potential up to 600mV and decreased thereafter. Higher power output (79.33mW/m2) was observed at 600mV poised potential under open circuit operation (OC). Closed circuit operation (CC) showed almost negligible power output due to continuous electron discharge against an external load (100Ω). However, CC operation resulted in the higher substrate (chemical oxygen demand (COD)) degradation [61.23% (control); 70.46% (OC; 600mV); 74.15% (CC; 600mV)] and total dissolved solids (TDS) removal [29.17% (control); 43.75% (OC; 600mV); 72.92% (CC; 600mV)] efficiencies compared to OC. Electron discharge and energy conversion efficiency was also observed to be higher with 600mV poised potential. Poising potential showed additional redox couples (−0.29±0.05mV) on cyclic voltammetry. Application of poised potential during startup phase will help to enrich electrochemically active consortia on anode resulting in improved performance of MFC. [Copyright &y& Elsevier]

Abstract: Single chambered mediatorless microbial fuel cell (MFC; non-catalyzed electrodes) was operated to evaluate the potential of bioelectricity generation from the treatment of composite waste vegetables (EWV) extract under anaerobic microenvironment using mixed consortia as anodic biocatalyst. The system was operated with designed synthetic wastewater (DSW; 0.98kgCOD/m3-day) during adaptation phase and later shifted to EWV and operated at three substrate load conditions (2.08, 1.39 and 0.70kgCOD/m3-day). Experimental data illustrated the feasibility of bioelectricity generation through the utilization of EWV as substrate in MFC. Higher power output (57.38mW/m2) was observed especially at lower substrate load. The performance of MFC was characterized based on the polarization behavior, cell potentials, cyclic voltammetric analysis and sustainable resistance. MFC operation also documented to stabilize the waste by effective removal of COD (62.86%), carbohydrates (79.84%) and turbidity (55.12%). [Copyright &y& Elsevier]

Abstract: Endocrine disruptive compounds (EDC) are a wide variety of chemicals which typically exert effects, either directly or indirectly, through receptor-mediated processes. They mimic endogenous hormones by influencing the activities of hormone activities even at nanogram concentrations and reported to disrupt the vital systems (e.g., the endocrine system) in aquatic organisms. The EDC are present in aquatic water bodies and sediments mainly due to the release of human and animal excreted waste. Estriol (E3) removal by adsorption process was investigated in this study to evaluate the potential of activated charcoal as adsorbent. Agitated non-flow batch sorption studies showed good E3 removal efficiency. Sorption kinetic data illustrated good fit with pseudo-first-order rate equation. Experimental data confirmed to linear Langmuir''s isotherm model. Neutral pH condition showed comparatively good sorption of E3. Adsorption capacity showed a consistent increasing trend with increase in the operating temperature [ΔH°, −9.189kJ/mol); ΔS°, 0.492J/molK) suggesting exothermic nature of E3 sorption process. Free energy (ΔG°) increased from 2.51 to 2.97kJ/mol with increase in temperature from 0 to 50°C. Further, E3 spiked distilled water, untreated domestic sewage and treated domestic sewage were studied in fixed bed column to assesses the potential of sorption process as tertiary unit operation in the ETP system. Total E3 concentration was determined quantitatively by employing direct competitive enzymatic-immuno assay (EIA) procedure. [Copyright &y& Elsevier]

Abstract: Influence of reactor configuration [biofilm/suspended growth] on fermentative hydrogen (H2) production and substrate degradation was evaluated employing anaerobic mixed consortia. Reactors were operated at acidophilic (pH 6.0) condition employing designed synthetic wastewater as substrate at an organic loading rate of 3.4Kg COD/m3-day with a retention time of 24h at 28±2 °C. Experimental data enumerated the influence of reactor configuration on both H2 production and wastewater treatment. Biofilm reactor (28.98mmol H2/day; 1.25Kg COD/m3-day) showed relatively efficient performance over the corresponding suspended growth configuration (20.93mmol H2/day; 1.08Kg COD/m3-day). Specific H2 yields of 6.96mmol H2/g-CODL-day (19.32mmol H2/g-CODR-day) and 5.03mmol H2/g-CODL-day (16.10mmol H2/g-CODR-day) were observed during stabilized phase of operation of biofilm and suspended growth reactors respectively. Higher concentration of VFA generation was observed in the biofilm reactor. Both the configurations recorded higher acetate concentration over other soluble metabolites indicating the dominance of acid-forming metabolic pathway during the H2 production process. [Copyright &y& Elsevier]