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Feasibility of integrating Microbial electrolysis cell (MEC) process with dark-fermentation process for additional hydrogen recovery as well as substrate degradation was demonstrated in the present study. MEC was employed in order to utilize the residual organic fraction present in the acidogenic effluents of dark fermentation process as substrate for hydrogen production with input of small electric current. MEC was operated at volatile fatty acids (VFA) concentration of 3000 mg/l under different poised potentials (0.2, 0.5, 0.6, 0.8 and 1.0 V) using anaerobic consortia as biocatalyst. Maximum hydrogen production rate (HPR), cumulative hydrogen production (CHP) (0.53 mmol/h and 3.6 mmol), dehydrogenase activity (1.65 μg/ml) and VFA utilization (49.8%) was recorded at 0.6 V. Bio-electrochemical behavior of mixed consortia was evaluated using cyclic voltammetry and by Tafel slope analysis. Microbial diversity analysis using denaturing gradient gel electrophoresis confirmed the presence of γ-proteobacteria (50%), Bacilli (25%) and Clostridia (25%)., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Bioremediation of selected endocrine disrupting compounds (EDCs)/estrogens viz. estriol (E3) and ethynylestradiol (EE2) was evaluated in bio-electrochemical treatment (BET) system with simultaneous power generation. Estrogens supplementation along with wastewater documented enhanced electrogenic activity indicating their function in electron transfer between biocatalyst and anode as electron shuttler. EE2 addition showed more positive impact on the electrogenic activity compared to E3 supplementation. Higher estrogen concentration showed inhibitory effect on the BET performance. Poising potential during start up phase showed a marginal influence on the power output. The electrons generated during substrate degradation might have been utilized for the EDCs break down. Fuel cell behavior and anodic oxidation potential supported the observed electrogenic activity with the function of estrogens removal. Voltammetric profiles, dehydrogenase and phosphatase enzyme activities were also found to be in agreement with the power generation, electron discharge and estrogens removal., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Microbially catalyzed treatment of wastewater was evaluated in both the anode and cathode chambers in dual chambered microbial fuel cell (MFC) under varying biocathode microenvironment. MFC operation with aerobic biocathode showed significant increment in both TDS (cathode, 90.2±1%; anode, 39.7±0.5%) and substrate (cathode, 98.07±0.06%; anode, 96.2±0.3%) removal compared to anaerobic biocathode and abiotic cathode operations (COD, 80.25±0.3%; TDS, 30.5±1.2%). Microbially catalyzed reduction of protons and electrons at cathode will be higher during aerobic biocathode operation which leads to gradual substrate removal resulting in stable bio-potential for longer periods facilitating salts removal. Bio-electro catalytic behavior showed higher exchange current density during aerobic biocathode operation resulting in induced electrochemical oxidation which supports the enhanced treatment. Anaerobic biocathode operation depicted relatively less TDS removal (anode, 16.35%; cathode, 16.04%) in both the chambers in spite of good substrate degradation (anode, 84%; cathode, 87.39%). Both the chambers during anaerobic biocathode operation competed as electron donors resulting in negligible bio-potential development., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Performance of microbial fuel cell (MFC) was evaluated with the function of phosphatase and dehydrogenase activities at increasing organic loading rate (OLR) (0.195kg chemical oxygen demand (COD)/m(3)-day; 0.458kg COD/m(3)-day; 0.911kg COD/m(3)-day; 1.589kg COD/m(3)-day). Variation in enzyme activities along with power generation and substrate degradation was observed during MFC operation with the function of organic loading rate (OLR). Phosphatase activity showed a decreasing trend with time from 24 to 36th hour depending on OLR which is a good sign of substrate utilization. Dehydrogenase activity was observed to be high at the 12th hour irrespective of the OLR. However, the activity was increased with increasing OLR. Higher dehydrogenase activity was observed at 1.589kg COD/m(3)-day representing the possibility of higher redox reactions. Higher power output was recorded at the 12th hour with 53.58mW/m(2) (0.195kg COD/m(3)-day) and 24th hour with 60.29mW/m(2) (0.458kg COD/m(3)-day) and 76.17mW/m(2) (0.911kg COD/m(3)-day). At higher OLR studied (1.589kg COD/m(3)-day), maximum power generation (49.86mW/m(2)) was observed at 12th hour indicating decreased performance. Electron discharge and recovery properties observed during MFC operation were supporting higher performance at 0.911kg COD/m(3)-day. Increase in OLR showed improvement in substrate degradation [OLR1, 56.32% (0.11kg COD/m(3)-day); OLR2, 56.42% (0.26kg COD/m(3)-day); OLR3, 59.53% (0.54kg COD/m(3)-day); OLR4, 64.40% (1.78kg COD/m(3)-day)]., (2009 Elsevier B.V. All rights reserved.)

Single chambered mediatorless microbial fuel cell (MFC Nafion-117 membrane) fabricated with non-catalyzed electrodes was operated with open-air cathode to evaluate bioelectricity generation from domestic wastewater under acidogenic conditions (pH, 6) using anaerobic mixed consortia as anodic biocatalyst. Experimental data illustrated the feasibility of bioelectricity generation from domestic wastewater treatment. A steady increase in MFC performance was observed from the first cycle (0.248 V; 27.3 mW/m(2); 1.06 W/kg COD(R)) during the startup phase prior to stabilization on fourth cycle (0.449 V; 144.6 mW/m(2); 4.64 W/kg COD(R)). Sharp increase in power generation was observed after the fourth hour (125.4 mW/m(2); 289.61 mA/m(2)) which continued up to the sixth hour (155.92 mW/m(2); 325.51 mA/m(2)) and gradually decreased thereafter. Voltammogram evidenced clear redox peaks (E(0)', -0.334 V) related to redox mediator NAD(+)/NADH (E(0)', -0.32 V) suggesting a strong reducing phase. Higher energy (1.33 J) was observed at the fourth hour in concurrence with the effective electron discharge and higher substrate degradation.

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 [DeltaH degrees , -9.189 kJ/mol); DeltaS degrees , 0.492 J/mol K) suggesting exothermic nature of E3 sorption process. Free energy (DeltaG degrees ) increased from 2.51 to 2.97 kJ/mol with increase in temperature from 0 to 50 degrees 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.

Function of microbial fuel cell (MFC) as bio-electrochemical treatment system in concurrence with power generation was evaluated with composite chemical wastewater at high loading conditions (18.6 gCOD/l; 56.8 gTDS/l). Two dual chambered MFCs [non-catalyzed graphite electrodes; mediatorless anode] were studied separately with aerated and potassium ferricyanide catholytes under similar anodic operating conditions [mixed consortia; pH 6]. Marked improvement in power output was observed at applied higher substrate loading rate for extended period of time without any process inhibition. Catholyte nature showed significant influence on power generation [ferricyanide-651 mV; 18.22 mA; 6230 mW/kg COD(R) (500 Omega); 2321.69 mA/m(2) (100 Omega); 11.80 mW/m(3) and aerated-578 mV; 10.23mA; 2450 mW/kg COD(R) (400 Omega); 1220.68 mA/m(2) (100 Omega); 5.64 mW/m(3)] but not on wastewater treatment efficiency. Along with enhanced substrate degradation, relatively good removal of color (31%) and TDS (51%) was also observed during MFC operation, which might be attributed to the diverse bio-electrochemical processes triggered due to substrate metabolism and subsequent in situ bio-potential (voltage) generation. Apart from power generation, various unit operations pertaining to wastewater treatment viz., biological (anaerobic) process, electrochemical decomposition and electrochemical oxidation were found to occur symbiotically in the anode chamber. Among them anaerobic metabolism is considered to be a crucial and important rate limiting step. In view of inherent advantages, function of MFC as integrated bio-electrochemical treatment system in the direction of various wastewater treatment operations can be exploited.

Influence of recirculation on the performance of anaerobic sequencing batch biofilm reactor (AnSBBR) was studied in the process of treating hypersaline (total dissolved inorganic solids (TDIS) approximately 26 g/l) and low biodegradable (BOD/COD approximately 0.3) composite chemical wastewater. Significant enhancement in the substrate removal efficiency and biogas yield was observed after introducing the recirculation to the system. Maximum efficiency (COD removal efficiency - 51%; SDR - 3.14 kg COD/cum-day) was observed at recirculation to feed (R/F) ratio of 2 (OLR - 6.15 kg C OD/cum-day; HLR - 2.30 cum (liquid)/cum day; UFV(A) - 0.023 m/h). Subsequent increase of R/F to 3 (OLR - 6.15 kg COD/cum-day; HLR - 3.07cum (liquid)/cum-day; UFV(A) - 0.035 m/h) resulted in reduction in COD removal efficiency (32%; SDR - 1.97 kg COD/cum-day). The enhanced performance of the system due to the introduction of recirculation was attributed to the improvement in the mass transfer between the substrate present in the bulk liquid and the attached biofilm. The hydrodynamic behavior due to recirculation mode of operation reduced the concentration gradient (substrate inhibition) of substrate and reaction by-products (VFA) resulting in mixed flow conditions.