T.R. Sreekrishnan

Indian Institute of Technology Delhi, New Dilli, NCT, India

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Publications (105)212.61 Total impact

  • A. Mehrotra · K. Kundu · T.R. Sreekrishnan
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    ABSTRACT: A possibility of using simultaneous sewage sludge digestion and metal leaching (SSDML) process at the thermophilic temperature to remove heavy metals and suspended solids from sewage sludge is explored in this study. Though thermophilic sludge digestion efficiently produces a stable sludge, its inability to remove heavy metals requires it to be used in tandem with another process like bioleaching for metal reduction. Previously, different temperature optima were known for the heterotrophs (thermophilic) responsible for the sludge digestion and the autotrophs involved in bioleaching (mesophilic), because of which the metal concentration was brought down separately in a different reactor. In our study, SSDML process was carried out at 50 °C (thermophilic) by using ferrous sulfate (batch-1) and sulfur (batch-2) as the energy source in two reactors. The concentration of volatile suspended solids reduced by >40% in both batches, while that of heavy metals zinc, copper, chromium, cadmium and nickel decreased by >50% in both batch-1 and batch-2. Lead got leached out only in batch-1. Using 16S rRNA gene-based PCR-denaturing gradient gel electrophoresis analysis, Alicyclobacillus tolerans was found to be the microorganism responsible for lowering the pH in both the reactors at thermophilic temperature. The indicator organism count was also below the maximum permissible limit making sludge suitable for agricultural use. Our results indicate that SSDML at thermophilic temperature can be effectively used for reduction of heavy metals and suspended solids from sewage sludge.
    No preview · Article · Jan 2016 · Journal of Environmental Management
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    ABSTRACT: Afly ash membrane developed by The Energy and Resources Institute (TERI), New Delhi was studied for its applicability in municipal wastewater treatment. In particular, the effect of aeration on preventing membrane fouling was studied. The velocity field generated by aeration was studied to understand how the rising bubbles would efficiently scour the membrane filter and prevent fouling. Particle image velocimetry was used to monitor the air bubble movement along the membrane surface. The optimal reactor configuration (membrane module orientation) for which the aeration would impart maximum shear over the membrane was determined using potable water. This reactor configuration was later used for the biological treatment of synthetic wastewater. The second aspect of the study involved designing a support system to improve the strength of the membrane. Membrane modules without any internal support were able to withstand trans-membrane pressures (TMP) up to 270 mmHg. Two types of frames/seperators were used to increase membrane strength. In one type of the frame, support was unidirectional and in another, bidirectional. Bidirectionallysupported membranes were able to withstanda TMP of 760 mmHg for a period of 7 days. At a constant filtration rate, a membrane bioreactor with more than one membrane in parallel operation was able to delay the fouling process than in a single membrane system due to lesser pressure across the membranes. As expected, membrane fouling took longer time in the systems operated at higher air flowrate due to better scouring action of the air bubbles.
    Preview · Article · Dec 2015
  • Sanjeev Kumar Prajapati · Anushree Malik · Virendra Kumar Vijay · Trichur Ramaswamy Sreekrishnan
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    ABSTRACT: Anaerobic digestion of algal biomass faces problems of low digestibility due to cell wall resistant and improper carbon to nitrogen ratio. In the present work a short duration method involving fungal crude enzyme based pretreatment of algal biomass was disclosed. Effect of fungal crude enzymes on algal biomass was assessed qualitatively though visual and microscopic observations and quantitatively through measuring algal biomass solubilization. Up to 50 % biomass COD solubilization was observed within 150 min of pretreatment under optimal conditions. Subsequent anaerobic digestion of pretreated algal biomass showed production of 324.38 mL CH4 g–1 VSfed as compared to 254.73 mL CH4 g–1 VSfed from untreated algal biomass. Interestingly, methane yield increased up to 413.89 mL g–1 VSfed when pretreated algal biomass was codigested with cattle dung. On the other hand, sugarcane bagasse had negative effect on algal biomass codigestion due to its poor digestibility. Overall, present attempt showed promising results by improving methane yield from algal biomass though pretreatment and codigestion.
    No preview · Article · Jul 2015 · RSC Advances
  • Pragya Gupta · T.R. Sreekrishnan · Shaikh Z. Ahammad
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    ABSTRACT: This work focuses on microbial granulation in hybrid anaerobic reactors (HAR). Five HARs were used in two sets of experiments and all were seeded with the same inoculum. The volume of inoculum added was 10%, 20%, 30%, 40% and 50% in the first and 13%, 15%, 18%, 23%, and 27% in the second set of experiment. The volume of inocula added affects the sludge volume index, which in the present study proves to be important parameter for granulation. The results suggest that if SVI during the reactor start-up is kept between 150 and 210, reactors were able to form granules. Outside this range in the present set-up, no granulation was observed due to increased biomass wash-out, causing decreased SRT. Higher methane production was achieved in reactors with good granulation. The DGGE profiles show that the non-granulating systems had lesser diversity, due to increased wash out. Archaeal profile gave better correlation for granulation. Granulating reactors were rich in aceticlastic methanogens over hydrogen utilizing groups, especially Methanosaetaceae. Both Methanosarcina and Methanosaeta are required for better granulation as confirmed quantitatively. Bacterial profile of granulating reactors were rich in acetogens. SEM (Scanning electron microscopy) pictures show that granules are dominated by Methanosaeta-like microbes. Thus, the sludge characteristics at the start-up are of vital importance as they influence the sludge quality developed during the reactor operation and also the microbial communities retained.
    No preview · Article · Jul 2015 · The Chemical Engineering Journal
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    Dataset: HZENG-216
    Shukla Pal · S. K. Gupta · T. R. Sreekrishnan · S. S. Maitra

    Full-text · Dataset · Jun 2015
  • Kapil Kumar · Shikhar Deep · Surindra Suthar · M.G. Dastidar · T.R. Sreekrishnan
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    ABSTRACT: A fuzzy logic-based diagnosis system was developed to optimize the process parameters for the decolourization of a real textile wastewater. A batch-scale colour removal experiment was conducted with a set of variable parameters of the process. The measured data of variables were implemented into the fuzzy inference system with Mamdani’s method. The fuzzy model incorporates the weights provided by an expert, avoids the crisp values and offers overlapping range between the different fuzzy sets. A fuzzy rule-based model was shaped to define essential quality parameters monitored as pH, temperature, inoculum concentrations and glucose concentration as inputs. The fuzzy-modelled values of decolourization were validated against the experimental values. Results suggested that modelled results could be validated with experimental data-sets, as supported by a significant correlation coefficient (r = 0.87). This study confirms the applicability of fuzzy logic for optimization of conditions in the decolourization process in textile wastewater treatment process.
    No preview · Article · Jun 2015 · Desalination and water treatment
  • Pragya Gupta · T. R. Sreekrishnan · Shaikh Ziauddin Ahammad
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    ABSTRACT: The effectiveness of anaerobic wastewater treatment is limited by pollutants in industrial wastewaters inhibiting microorganisms, leading to digester failure. Acclimatization enables the microorganisms to develop the capacity to degrade them faster, preventing reactor failure. The present study focuses on the acclimatization of anaerobic sludge to treat two pollutants, chromium (VI) and 4-chlorophenol (4-CP), in two separate batch reactors. Microbial community profiles were obtained to find their effects on microbial populations. Both chemical and microbial data indicated inhibition of biogas production. A 50% reduction in methane concentration was observed at 150 ppm of Cr (VI), whereas for 4-CP, it was observed at 200 ppm. Sulfate-reducing bacteria present in the anaerobic sludge helps to remove heavy metals by facilitating the formation of insoluble metal sulfides. The effect of their presence in an anaerobic system containing 150 ppm Cr (VI) was studied by adding 30-mM sodium molybdate, which inhibited the sulfate reducing bacteria.
    No preview · Article · May 2015 · Journal of Hazardous, Toxic, and Radioactive Waste
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    Mohammad Zain Khan · Satyendra Singh · Saima Sultana · Trichur Ramaswamy Sreekrishnan · Shaaikh Ziauddin Ahammad
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    ABSTRACT: A comparative study on the degradation of acid navy blue R (ANB) and reactive orange 16 (RO 16) was performed in two identical microbial fuel cells (MFCs) under similar conditions and the microbial communities were quantified using quantitative real time polymerase chain reaction (qPCR). Electricity and methane gas were produced as the end products along with significant removal of chemical oxygen demand (COD) during the study. The overall performance in terms of degradation rate, COD removal efficiency and biogas production rates were slightly better in case of the reactor using RO 16 as carbon source while electricity production was slightly greater in reactor treating ANB. Negative standard reduction potential of the reaction mixture indicates the presence of oxidized species in the reactor. Scanning electron microscopic images shows the presence of diatoms and rod shaped bacteria in the mixed microbial culture and also confirmed the formation of biofilm on anode surface. The qPCR technique was used as a quantitative tool to estimate the abundance of methanogens, sulphate reducing bacteria (SRBs) and electrochemically active Geobacter species. The relative abundance of methanogens was comparatively higher and Geobacter was lower in case of the reactor treating RO 16. Although the output power was low, the technique can be used for effective degradation of complex and toxic compounds.
    Full-text · Article · May 2015 · New Journal of Chemistry
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    Meenu Chhabra · Saroj Mishra · Trichur Ramaswamy Sreekrishnan
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    ABSTRACT: Laccases have good potential as bioremediating agents and can be used continuously in the immobilized form like many other enzymes. In the present study, laccase from Cyathus bulleri was immobilized by entrapment in Poly Vinyl Alcohol (PVA) beads cross-linked with either nitrate or boric acid. Immobilized laccase was used for dye decolorization in both batch and continuous mode employing a packed bed column. The products of degradation of dye Acid Red 27 were identified by LC MS/MS analysis. The method led to very effective (90%) laccase immobilization and also imparted significant stability to the enzyme (more than 70% after 5 months of storage at 4°C). In batch decolorization, 90-95% decolorization was achieved of the simulated dye effluent for up to 10-20 cycles. Continuous decolorization in a packed bed bioreactor led to nearly 90% decolorization for up to 5 days. The immobilized laccase was also effective in decolorization and degradation of Acid Red 27 in the presence of a mediator. Four products of degradation were identified by LC-MS/MS analysis. The immobilized laccase in PVA-nitrate was concluded to be an effective agent in treatment of textile dye effluents.
    Full-text · Article · Apr 2015 · Journal of Environmental Health Science and Engineering
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    Full-text · Dataset · Apr 2015
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    Full-text · Dataset · Apr 2015
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    ABSTRACT: The aim of the present work was to characterize the impedance response of an air-cathode MFC operating in a continuous mode and to determine intrinsic properties that define its performance which are crucial to be controlled for scalability purposes. The limiting step on electricity generation is the anodic electrochemically-active biofilm, independently of the external resistance, Rext, utilized. However, for Rext below 3kΩ the internal impedance of the bioanode remained invariable, in good correspondence to the power density profile. The hydraulic retention time (HRT) had an effect on the impedance of both the bioanode and the air-cathode and especially on the overall MFC. The lowest HRT at which the MFC was operable was 3h. Yet, the variation on the HRT did not have a significant impact on power generation. A two constant phase element-model was associated with the EIS response of both bioanode and air-cathode, respectively. Consistency was found between the CPE behaviour and the normal power-law distribution of local resistivity with a uniform dielectric constant, which represented consistent values with the electrical double layer, the Nernst diffusion layer and presumably the biofilm thickness. These results have future implications on MFC monitoring and control, as well as in providing critical parameters for scale-up. Copyright © 2015 Elsevier B.V. All rights reserved.
    Full-text · Article · Apr 2015 · Bioelectrochemistry
  • S. M. Acharya · K. Kundu · T. R Sreekrishnan
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    ABSTRACT: Accumulation of volatile fatty acids (VFAs) under overloading conditions in anaerobic reactors is a common problem. There is a need to stop this accumulation to improve reactor stability. In this study, propionate-, butyrate-, and acetate-degrading cultures were enriched and used as inocula in a mesophilic two-stage reactor to improve system stability. The performance of a test reactor was compared with that of a control reactor that was not seeded with specific VFA-degrading inocula under normal and overloading conditions. The reactors were fed with simulated wastewater having a chemical oxygen demand (COD) of 10,000mgL-1. The test reactor inoculated with VFA-degrading cultures showed better performance in terms of methane production, COD removal, and VFA degradation. Also, after two consecutive organic shocks (influent COD 20,000mgL-1) the test reactor recovered within four days and low levels of VFAs, especially propionate (429mgL-1), were observed. In contrast, in the control reactor the concentration of VFA did not decline to preshock levels, even after five days of two consecutive shocks. PCR-denaturing gradient gel electrophoresis analysis using 16S rRNA gene amplicons also indicated a significant difference in archaeal community structure in the control and test reactors. Methanosarcinaceae was found dominant in the test reactor whereas in the control reactor an equal abundance of both Methanosaetaceae and Methanosarcinaceae was observed. Specific methanogenic activity also suggested higher acetoclastic and hydrogenotrophic activity of the sludge in the test reactor. Overall, using enriched culture as inocula resulted in a more balanced and robust methanogenic consortium and in improved system stability, with efficient degradation of the high concentration of VFAs.
    No preview · Article · Jan 2015 · Journal of Environmental Engineering
  • Kapil Kumar · Surindra Suthar · M. G. Dastidar · T. R. Sreekrishnan
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    ABSTRACT: The present study was undertaken to investigate the potential of enriched indigenous sulfur-and-iron-oxidizing microorganisms in the bioleaching of Cu, Ni, Zn and Fe from textile sludges by using elemental sulfur and ferrous sulfate (FS), respectively, as an energy source under batch conditions. The experiments were performed with three different textile sludges (S1, S2 and S3) at initial neutral pH of the sludges procured from different parts of the country i.e., UP, Haryana and Punjab. The three sludges used were not only procured from different parts of the country but also differ in physiochemical characteristics. The extent of heavy metals solubilization in each sludge was found to be different using sulfur- and iron-oxidizing microorganisms. The results of the study indicate that sulfur-oxidizing microorganisms were found more efficient in the bioleaching process, irrespective of any sludge. The use of sulfur-oxidizing microorganisms led to higher solubilization of heavy metals and after 7 days of bioleaching about 84–96% Cu, 64–78% Ni, 81–92% Zn and 74–88% Fe were removed compared to 62–73% Cu, 62–66% Ni, 74–78% Zn and 70–78% Fe using iron-oxidizing microorganisms. This study had shown the feasibility of applying the bioleaching process to textile sludge contaminated with heavy metals. The results of the present study indicate that the bioleached sludge would be safer for land application.
    No preview · Article · Nov 2014 · Geomicrobiology
  • Kapil Kumar · M.G. Dastidar · T.R. Sreekrishnan
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    ABSTRACT: In search for a cheaper energy source, this study was undertaken to investigate the potential of mixed culture for the decolorization of Methylene blue (MB) and Remazol black B (RBB) using glucose, molasses, and cheese whey as an energy source for microbial growth in aerobic batch reactor. The experiments were performed with synthetic solutions of both the dyes ranging from 25 to 300 mg l−1. The results show that the decolorization and microbial growth was affected by the increase in concentration of dyes leading to the decreased decolorization of dyes. The presence of glucose was found to be more efficient as compared to molasses and cheese whey. After 36 h, mixed culture was able to decolorize MB up to 83, 59, and 54% and RBB up to 80, 58, and 52% in the presence of glucose, molasses, and cheese whey, respectively, at 300 mg l−1 initial dye concentration. The maximum specific uptake was 57, 51, and 52 mg g−1 in presence of glucose, molasses, and cheese whey, respectively, at 300 mg l−1 initial dye concentration of RBB. The maximum specific uptake was 58, 51, and 53 mg g−1 in the presence of glucose, molasses, and cheese whey, respectively, at 300 mg l−1 initial dye concentration of MB. The results of this study shall be useful to develop a suitable decolorization process for the treatment of dye-contaminated wastewater or wastewater contaminated with a variety of dyes.
    No preview · Article · Oct 2014 · Desalination and water treatment
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    Arpita Ghosh · Manisha Ghosh Dastidar · T. R. Sreekrishnan
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    ABSTRACT: The present study was conducted in batch bioreactors to evaluate the removal of color, chromium, and chemical oxygen demand (COD) from Acid Orange 86 (i.e., chromium complex dye) solution by growing Aspergillus sp. isolated from the sludge of a textile industry. The organism was found to grow in the dye solution and was tolerant up to a concentration of 10,000 mg/L of the dye. During its growth, Aspergillus sp. effectively decolorized and removed chromium from the dye solution at a concentration up to 10,000 mg/L. After 50 h of contact time, the color removal decreased from 98.2 to 42% and the chromium removal decreased from 100 to 50% by increasing the initial concentration of dye from 50 to 10,000 mg/L at pH 5 using 10% v/v inoculum concentration. The COD removal after decolorization and biosorption decreased from 69.83 to 49% by increasing the initial concentration of dye from 50 to 1,000 mg/L. Biodegradation and biosorption of the dye during decolorization were indicated by gas chromatography-mass spectrometry and ultraviolet-visible spectroscopic methods. Scanning electron micrographs indicated the structural distortion of the fungal biomass after microbial treatment. Phytotoxicity tests showed that the biotreated wastewater was less toxic to Cicer arietinum seeds.
    Full-text · Article · Oct 2014 · Journal of Hazardous, Toxic, and Radioactive Waste
  • Kapil Kumar · M. G. Dastidar · T. R. Sreekrishnan
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    ABSTRACT: The present study was undertaken to investigate the tolerance levels of indigenous sulfur-oxidizing micro-organisms to Methylene blue (MB), Remazol black B (RBB), and mixture of both the dyes (DM) during bioleaching of heavy metals from sewage sludge. The experiments were performed with anaerobically digested sewage sludge at initial neutral pH of the sludge containing 0–35,000 mg/l of the MB, RBB, and DM. The results show that the bioleaching process was affected by the increase in concentration of MB, which decreased the growth of indigenous sulfur-oxidizing micro-organisms leading to the slow rate of decrease in pH and hence decreased solubilization of metals. Similar effects were observed on the activity of indigenous sulfur-oxidizing micro-organisms using RBB and a mixture (DM) of MB and RBB. The presence of RBB and DM were found to be more toxic as compared to MB at the same initial concentration of the dyes. At initial concentration of 30,000 mg/l, a drastic reduction in pH drop was observed with decreased solubilization of metals, irrespective of any dye. The results of the present study shall be useful to develop a suitable bioleaching process for the sludges contaminated with a variety of dyes.
    No preview · Article · Sep 2014 · Desalination and water treatment
  • Surajbhan Sevda · T R Sreekrishnan
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    ABSTRACT: In this study, a dual chamber MFC was constructed for simultaneous removal of organic matter and nitrogenous pollutants and bioelectricity generation from synthetic and complex industrial wastewaters and it was operated in batch and continuous mode. When the cell potential was stable after 16 days of batch mode operation, the MFC was converted to continuous mode (from batch mode) and operated for 125 days with different organic loading rates (OLR) and ammonia loading rates (ALR) and fixed hydraulic retention time (HRT) of 40 h. The OLR of 1.49 kg COD m(-3) d(-1) and ALR of 0.58 kg NH3(-) m(-3) d(-1), for anodic and cathodic chambers, respectively, gave the best results. The highest value of cell potential on these OLRs was 310 mV with current density of 85.11 mA m(-2), power density of 26.38 mW m(-2) and volumetric power density of 192.20 mW m(-3). During this period, COD reduction was 78-83% in the anodic chamber and the ammonia reduction was 36-38%. After stable operation with synthetic wastewater one case study was performed with complex industrial wastewater. Continuous mode operation was performed at two different OLR and HRT with a constant ALR. A stable power density and volumetric power density of 23.56 mW m(-2) and 112.50 mW m(-3), respectively were achieved after 24 days of continuous operation at an OLR of 0.35 kg COD/m(3) day with an ALR of 0.43 kg NH3(-) m(-3) day(-1) and corresponding HRT of 68 h. A maximum of 89% COD removal and 40% removal of ammonia was obtained after 50 days. A stable voltage of 300 mV was obtained across 1000 Ω resistance. These findings suggest that BMFC can be used for the treatment of industrial wastewater, with carbon removal in anodic chamber and electricity generation.
    No preview · Article · Sep 2014 · Journal of Environmental Science and Health Part A Toxic/Hazardous Substances & Environmental Engineering
  • Mohammad Zain Khan · Satyendra Singh · Trichur Ramaswamy Sreekrishnan · Shaikh Ziauddin Ahammad
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    ABSTRACT: Anaerobic digestion of textile azo-dyes is very effective and widely used since it is cost-effective and energy efficient. The present study deals with the anaerobic degradation of reactive orange 16 (RO 16, an azo-dye) using mixed microbial culture. 80 mL each of three different concentrations of RO 16 (100, 200 and 300 ppm) were taken in 150 mL serum vials containing 20 mL of mixed microbial culture and studied periodically. HPLC and UV data revealed that more than 90% of the color was removed within the very first week of the reactor start up. A high COD removal efficiency (≥80%) was achieved after the steady state. Methane and VFAs were produced, and monitored by Gas chromatography. The pH of the medium was slightly acidic favoring methanogenic activity. The diversity of the microbial community was studied by denaturing gradient gel electrophoresis (DGGE) of the polymerase chain reaction (PCR) amplified products of the bacterial and archeal 16S rRNA and the results showed the presence of significant population of acetogens as well as methanogens in the reactor. Quantitative real time PCR (qPCR) was used for the quantitative analysis of some major genera. This study showed that strategic operation of anaerobic digester can be a viable option for effective decolorization of complex substrate resulting into energy (biogas) generation.
    No preview · Article · Sep 2014 · RSC Advances
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    ABSTRACT: The present study evaluates the performance of air-cathode microbial fuel cells (MFCs) under alternating open circuit/closed circuit (OC/CC) modes and its effect on independent-electrode and full-cell potentials, power output (at different external resistances) and the polarization behaviour of the electrodes. Three different types of feeds were evaluated using this approach: (1) phosphorus buffer solution (PBS) with acetate as carbon source, (2) glucose-rich synthetic wastewater, and (3) sewage from wastewater treatment plant enriched with fermented molasses. When MFCs were suddenly switched to CC from CC and then again back to CC from CC, the behaviour of the anodes vs reference electrode (Ag/AgCl,3 M KCl) was monitored. When electric circuit of the MFCs was switched from open to closed circuit, for all cases: (a) the anode potential-shift (vs Ag/AgCI) reallocated in the positive direction in about 200-400 mV, (b) the air-cathode potential-shift (vs Ag/AgCI) reallocated in the negative direction in about 10-25 mV, and (c) the cell-potential difference started at around 0 mV and progressively increased as the MFC reached stability. This behaviour was consistently reproduced during different OC/CC cycles. The systems studied delivered good performance with both controlled media and industrial wastewater. Additionally, this study provides insightful characterization of the independent-electrode behaviours.
    Full-text · Article · Jul 2014 · Biochemical Engineering Journal

Publication Stats

2k Citations
212.61 Total Impact Points


  • 2001-2016
    • Indian Institute of Technology Delhi
      • Department of Biochemical Engineering and Biotechnology
      New Dilli, NCT, India
  • 2010-2015
    • IIT Kharagpur
      Khargpur, West Bengal, India
  • 2006
    • Tarbiat Modares University
      • Department of Chemical Engineering
      Teheran, Tehrān, Iran
  • 2000
    • Indian Institute of Technology Ropar
      Rūpar, Punjab, India
  • 1993-1998
    • Institut national de la recherche scientifique
      • Eau Terre Environnement Centre
      Quebec City, Quebec, Canada