T R Sreekrishnan

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

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Publications (58)115.28 Total impact

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    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.
    Journal of Environmental Science and Health Part A Toxic/Hazardous Substances & Environmental Engineering 09/2014; 49(11):1265-1275.
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    Biochemical Engineering Journal 07/2014; 90:294-300. · 2.58 Impact Factor
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    International Journal of Green Energy 05/2014; · 2.07 Impact Factor
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    ABSTRACT: Antibiotic resistance (AR) is often rooted in inappropriate antibiotic use, but poor water quality and inadequate sanitation exacerbate the problem, especially in emerging countries. An example is increasing multi-AR due to mobile carbapenemases, such as NDM-1 protein (coded by blaNDM-1 genes), which can produce extreme drug-resistant phenotypes. In 2010, NDM-1 positive isolates and blaNDM-1 genes were detected in surface waters across Delhi and have since been detected across the urban world. However, little is known about blaNDM-1 levels in more pristine locations, such as the headwaters of the Upper Ganges River. This area is of particular interest because it receives massive numbers of visitors during seasonal pilgrimages in May/June, including visitors from urban India. Here we quantified blaNDM-1 abundances, other AR genes (ARG) and coliform bacteria in sediments and water column samples from seven sites in the Rishikesh-Haridwar region of the Upper Ganges and five sites on the Yamuna River in Delhi to contrast blaNDM-1 levels and water quality conditions between season and region. Water quality in the Yamuna was very poor (e.g., anoxia at all sites), and blaNDM-1 abundances were high across sites in water (5.4 ± 0.4 log(blaNDM-1·mL-1); 95% confidence interval) and sediment (6.3 ± 0.7 log(blaNDM-1·mg-1)) samples from both seasons. In contrast, water column blaNDM-1 abundances were very low across all sites (2.1 ± 0.6 log(blaNDM-1·mL-1)) in February in the Upper Ganges and water quality was good (e.g., near saturation oxygen). However, per capita blaNDM-1 levels were 20 times greater in June in the Ganges water column relative to February and blaNDM-1 levels significantly correlated with fecal coliform levels (r=0.61; p=0.007). Given waste management infrastructure is limited in Rishikesh-Haridwar; data imply blaNDM-1 levels are higher in visitor's wastes than local residents, which results in seasonally higher blaNDM-1 levels in the river. Pilgrimage areas without adequate waste treatment are possible "hot spots" for AR transmission, and waste treatment must be improved to reduce broader AR dissemination via exposed returning visitors.
    Environmental Science & Technology 02/2014; · 5.26 Impact Factor
  • K Kundu, I Bergmann, M Klocke, S Sharma, T R Sreekrishnan
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    ABSTRACT: This study aimed to analyse the effect of sudden temperature increases (in the range of 45-65°C) on the performance and the microbial community structure of a hybrid anaerobic reactor. The reactor recovered with time after every temperature shock up to the operating temperature of 55°C. At 55°C, a 10°C shock resulting in an operating temperature of 65°C, deteriorated the reactor's performance. At this condition, both, the diversity and the relative abundance of methanogenic groups, especially of Methanosaetaceae, were significantly affected as observed by DGGE fingerprinting and quantitative PCR. In contrast, at lower temperatures (i.e., 45 and 55°C), thermal shocks seemed to have less effect due to the presence and maintenance of thermophilic strains, which prevented system deterioration. At 65°C, the absence of any acetoclastic methanogen is assumed to be the cause of system failure.
    Bioresource Technology 01/2014; · 4.75 Impact Factor
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    ABSTRACT: Adequate information is available on colour and organics removal in batch mode using pure microbial cultures from dye contaminated wastewater. There was a need to develop environment friendly and cost effective treatment technique for actual field conditions. Therefore, the present study was undertaken with an aim to evaluate the potential of acclimatized mixed microbial consortia for the removal of colour and organics from real textile wastewater. Experiments were performed in laboratory scale activated sludge process (ASP) unit under steady state condition varying mixed liquor volatile suspended solids (MLVSS) (2500, 3500 and 5000 mg/l) and hydraulic retention time (HRTs) (18, 24 and 36 h). The results showed that decolourization and chemical oxygen demand (COD) removal increased with increase in MLVSS and HRT. At 18 h HRT, decolourization was found to be 46%, 54% and 67%, which increased to 67, 75 and 90% (36 h HRT) at 2500, 3500 and 5000 mg/l MLVSS respectively. COD removal was found to be 62, 73 and 77% (at 18 h HRT) which increased to 77, 85 and 91% (36 h HRT) at 2000, 3500 and 5000 mg/L MLVSS respectively. On the basis of the results obtained in this study suitable treatment techniques can be developed for the treatment of wastewater contaminated with variety of dyes in continuous mode of operation. This shall have the advantage of treatment of larger quantity of wastewater in shorter duration.
    Water Resources and Industry. 01/2014;
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    ABSTRACT: A comparative study was undertaken using indigenous sulfur-oxidizing microorganisms and iron-oxidizing microorganisms in separate 12 litre continuous stirred tank reactors (CSTRs) for solubilization of heavy metals from anaerobically digested sewage sludge. The CSTRs were operated at hydraulic retention times (HRTs) ranging from 4 to 10 days using sewage sludge feed having near neutral pH. The pH, oxidation-reduction potential (ORP) and solubilization efficiency of metals were found to be highly dependent on HRT and an increase in HRT led to higher solubilization of metals in both the CSTRs. In both the CSTRs, the CSTR operated with sulfur-oxidizing microorganisms at an HRT of 8 days was found to be optimum in solubilizing 58% Cu, 52% Ni, 72% Zn and 43% Cu from the sludge. The nutrient value, nitrogen and phosphorus of bioleached sludge was also conserved (<20% loss) at 8 days HRT. The metals fractionation study conducted using BCR sequential extraction procedure suggested that most of the metals remaining in the bioleached sludge were in the more stable fractions (F3 and F4) and, therefore, can be safely apply as a fertilizer on land.
    Journal of Environmental Science and Health Part A Toxic/Hazardous Substances & Environmental Engineering 01/2014; 49(1):93-100.
  • S. Abubakkar, K. Kundu, T. R. Sreekrishnan
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    ABSTRACT: Background Process upset due to volatile fatty acid accumulation is one of the major drawbacks of anaerobic treatment of wastewater. The performance of an Anaerobic Rotating Biological Contactor (AnRBC) was studied under normal operating conditions as well as shock loadings of propionic acid, for its ability to enhance the conversion of hydrogen to methane. These results were compared with that of a reactor lacking the enhanced gas–liquid hydrogen transfer mechanism, a conventional anaerobic digester. ResultAnRBC exhibited lower concentrations of hydrogen in the headspace (300–600 ppm) under both normal and shock loading conditions, and also showed more number of hydrogenotrophic methanogens on the denaturing gradient gel electrophoresis (DGGE) profile of 16S rRNA gene amplicons, both in terms of intensity and band numbers (4 in AnRBC and 2 in anaerobic digester). Conclusion This study showed that AnRBC is able to maintain lower hydrogen partial pressure at both normal operating and shock loading conditions due to the abundance of hydrogenotrophic methanogens and good gas–liquid hydrogen transfer efficiency. This finding should encourage the commercial exploitation of AnRBC for the treatment of wastewaters, especially that containing easily acidifiable organic compounds, which causes instability in the operation through souring.
    Journal of Chemical Technology & Biotechnology 01/2014; · 2.50 Impact Factor
  • K Kundu, I Bergmann, S Hahnke, M Klocke, S Sharma, T R Sreekrishnan
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    ABSTRACT: Industrial effluents differ in their organic composition thereby providing different carbon sources to the microbial communities involved in its treatment. This study aimed to investigate the correlation of microbial community structure with wastewater composition and reactor's performance. Self-immobilized granules were developed in simulated wastewater based on different carbon sources (glucose, sugarcane molasses, and milk) in three hybrid anaerobic reactors operated at 37˚C. To study archaeal community structure, a polyphasic approach was used with both qualitative and quantitative analysis. While PCR-denaturing gradient gel electrophoresis of 16S rRNA gene did not reveal major shifts in diversity of archaea with change in substrate, quantification of different groups of methanogens and total bacteria by real-time PCR showed variations in relative abundances with dominance of Methanosaetaceae and Methanobacteriales. These data were supported by differences in the ratio of total counts of archaea and bacteria analyzed by catalyzed reporter deposition - fluorescence in situ hybridization. During hydraulic and organic shocks, the molasses-based reactor showed best performance followed by the milk- and the glucose-based reactor. The study indicates that carbon source shapes the microbial community structure more in terms of relative abundance with distinct metabolic capacities rather than its diversity itself.
    Journal of Biotechnology 08/2013; · 3.18 Impact Factor
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    ABSTRACT: Bioelectricity production from microbial fuel cell (MFC), fed with synthetic wastewater can achieve both wastewater treatment and energy production. Two different types of separators were used in this study to compare their performance in an air cathode MFC. Power generation and substrate utilization from the wastewater was compared for these membranes. The maximum power density obtained with Zirfon® was 424.50 mW/m2 and of 16.98 W/m3 (volumetric) while with Fumasep® was 38.03 mW/m2 and 1.52 W/m3 (volumetric). The internal resistance obtained with Zirfon® increased from initial 0.38 Ω cm2 to 1.72 Ω cm2 while with Fumasep® increased from 2.57 Ω cm2 to 10.92 Ω cm−2 at the end of the experiment. The results showed that the MFC with Zirfon® stabilized early and the anodic and cathodic cell potentials reached maximum earlier as compared to Fumasep®. Impedance spectra confirmed the lower resistance of the Zirfon® as compared to Fumasep® and this may be the reason for its better performance. Zirfon® might be a good option for the future scale up of MFCs because of its low cost and low internal resistance in comparison to other membranes.
    Chemical Engineering Journal 05/2013; 228:1-11. · 3.47 Impact Factor
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    ABSTRACT: Microbial fuel cells (MFCs) present a novel method for simultaneous bioelectricity generation and wastewater treatment. In this study, an air–cathode MFC with membrane-electrode assembly was operated over three batch cycles (total of 160 days) and results indicated that molasses mixed sewage wastewater (high strength wastewater) containing 9978 mg/L of chemical oxygen demand (COD) could be used as substrate to produce bioelectricity with this system. Three different compositions of wastewater were used as substrate. The original wastewater, half-diluted wastewater and centrifuged wastewater were used as substrate in MFCs. Maximum voltage output of 762 mV and maximal power density of 382.5 mW/m2 (5.06 W/m3) were obtained with the original wastewater by the 14th day of operation. During this time the system evolved to 0.93 Ω cm−2 internal resistance and 59% removal of the total COD were achieved. Centrifuged wastewater showed poor performance in terms of power production (0.12 mW/m2 or 4.2 mW/m3), presumably due to organic substrate limitations. The MFC running on diluted wastewater showed a power density of 56.17 mW/m2 (2.25 mW/m3), with 70% COD removal. Energy-Dispersive X-ray spectroscopy (EDX) analysis, together with other characterization methods, confirmed the breakdown of organic compounds in the wastewater, EDX and Scanning Electron Microscopy (SEM) revealed the surface morphology of the materials utilized and showed the evolution in electrode and membrane composition after the long term MFC processes. Denaturing Gradient Gel Electrophoresis (DGGE) profiles showed the presence of mixed populations enclosing the electrochemically-active bacteria that established a biofilm on the anode surface and as such differed from the suspended bacterial community in the anode medium. These results demonstrate that complex wastewater can be used as a substrate for power generation in MFCs and also can be treated with high COD removal efficiencies.
    Applied Energy 01/2013; 105:194-206. · 4.78 Impact Factor
  • Kankana Kundu, Shilpi Sharma, T R Sreekrishnan
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    ABSTRACT: Poor understanding of the response of microbial communities to sudden changes in organic and hydraulic loads is one of the major reasons for the inability to prevent operational instabilities in anaerobic reactors. Effect of changes in hydraulic retention time (HRT) and organic loading rate (OLR) on reactor performance and its anaerobic microbial community were investigated in two anaerobic hybrid reactors operated at 37 and 55°C. HRT was reduced stepwise, while OLR was increased along with influent chemical oxygen demand at fixed HRT until the performance of reactor deteriorated. The profile of archaeal 16S rRNA gene amplicons, resolved by denaturing gradient gel electrophoresis, reflected system status during disturbances. The more diverse archaeal community in the reactor operated at 37°C showed better performance than the communities present at 55°C at higher OLR and shorter HRT, suggesting that higher diversity is indicative of more stable operation of reactors despite organic and hydraulic shocks.
    Bioresource Technology 12/2012; 129C:538-547. · 4.75 Impact Factor
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    ABSTRACT: Production of hydrogen sulphide by sulphate reducing bacteria (SRB) is a serious problem in anaerobic wastewater treatment, because it causes corrosion and reduces the value of methane in the biogas produced. The surface and adhesion characteristics of SRB as measured through the zeta potential are different from those of methanogens. We therefore tested the hypothesis that by choosing a carrier material with the proper surface characteristics (zeta potential) it should be possible to selectively immobilize methanogens while excluding SRB. In a series of batch tests with different support materials complete elimination of SRB was obtained on supports made of nylon, a result in line with our original hypothesis. Maximum preferential immobilization of methanogens was obtained at a temperature of 37oC with media containing volatile fatty acids (VFA) as the carbon source. Preferential immobilization of methanogens was achieved in an anaerobic fluidized bed reactor (AFBR) with nylon granules as support and in an anaerobic rotating biological contactor (ARBC) with acrylic disc as support. H2S-free biogas containing 63 % and 38 % methane were obtained from the AFBR and ARBC, respectively.
    RSC Advances 11/2012; · 2.56 Impact Factor
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    ABSTRACT: The present study deals with comparative evaluation of three different plants species, i.e. Canna indica L., Typha angustifolia L. and Cyperus alternifolius L. planted vertical constructed wetlands (CWs) microcosms for Cu, Cr, Co, Ni and Zn removal from aqueous solution. The effects of depth of the gravel beds were also studied in order to explore possibilities of development of compact constructed wetlands. Linear regression analysis was carried out for predicting the final removal efficiencies by variation of the treatment time and the bed depth of filter materials. To determine the removal mechanism and mobility of heavy metals in constructed wetlands, accumulation of these metals in gravel, roots, stem and leaves of plant species were investigated. Results demonstrate that the wetland bed depth has significant, direct effect on final heavy metal removal efficiencies. Considering three different plant species, Zn removal was found to be highest (99.3% in T. angustifolia planted CWs in 72 h of treatment time), and Co removal was found to be lowest (54.6% in T. angustifolia planted CW in 72 h of treatment time).
    Chemical Engineering Journal 11/2012; 211-212:501-507. · 3.47 Impact Factor
  • S Bhuvanesh, N Maneesh, T R Sreekrishnan
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    ABSTRACT: This study was aimed at denitrification of wastewater using a hybrid anoxic reactor (HAR), which uses self immobilized microbial granules under fluidized condition. Granulation of the denitrifying biomass was studied in the HAR with methanol and acetate as carbon sources. It was observed that by the end of 15day almost spherical granules with a settling velocity of 1.5cm/s and a mean diameter of 0.5mm were produced. By stepwise increment of the influent nitrate concentration, the removal rate reached 740g NO(3)-N/m(3)day with a removal efficiency of almost 100% at a hydraulic retention time of 6h or higher. For complete denitrification, the ratio of the organic substrate required to amount of nitrate nitrogen removed was as low as 2.2g COD/g NO(3)-N. The study was then extended to denitrifying a nitrified toxic industrial effluent. Denitrification was on par with the synthetic wastewater and efficiency of more than 95% was achieved.
    Bioresource Technology 10/2012; 129C:78-84. · 4.75 Impact Factor
  • Kankana Kundu, Shilpi Sharma, T R Sreekrishnan
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    ABSTRACT: Lack of knowledge about the microbial consortia involved in wastewater treatment at different operating temperatures, is a major reason for failure of anaerobic reactors in field applications. Present study was undertaken to correlate performance of hybrid anaerobic reactors operating at different temperatures (37, 45 and 55 °C) to structures of archaeal and bacterial communities involved. Self-immobilized granules were developed in the reactors continuously fed with synthetic wastewater (10,000 mg COD l(-1)) and operated at an organic loading rate of 2.22 kg COD m(-3) day(-1) and hydraulic retention time of 5 days. The reactor operated at 37 °C showed the best performance as well as the most diverse microbial community revealed by PCR-denaturing gradient gel electrophoresis analysis using 16S rRNA gene amplicons. Sequences derived from reactors operating at higher temperatures revealed presence of different methanogens, but lesser diversity caused a drop in COD degradation capability of the system indicating successful operation at low loading conditions.
    Bioresource Technology 05/2012; 118:502-11. · 4.75 Impact Factor
  • Surajbhan Sevda, T R Sreekrishnan
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    ABSTRACT: The aim of this study was to investigate the feasibility of using agar salt bridges for proton transport in Microbial Fuel Cells (MFC). It also tries to elucidate and effect of mediators on electricity production from wastewaters through experimentation using a simulated wastewater. In order to offset the very high cost of proton exchange membrane, salt bridges have been used in dual chamber MFCs. When the concentration of salt was varied in agar salt bridges from 1% to 10%, the volumetric power density changed from 1.71 to 84.99 mW/m(3) with a concomitant variation in power density from 0.32 to 16.02 mW/m(2). The maximum power density was observed at 5% salt concentration with 10% agar, which was accompanied by 88.41% COD reduction. In the case of methylene blue (0.01 mM) as the electron mediator, the voltage and current generation were 0.551 V and 0.47 mA, respectively. A maximum open circuit voltage of 0.718 V was seen at 0.08 mM methylene blue concentration, whereas maximum power densities of 17.59 mW/m(2) and 89.22 mW/m(3) were obtained. Different concentrations of neutral red were also tried out as mediators. A maximum open circuit voltage of 0.730 V was seen at 0.01 mM neutral red, corresponding to a power density of 12.02 mW/m(2) (volumetric power density of 60.97 mW/m(3)). Biofilm formation on the electrode surface was not observed in the presence of mediators, but was present in the absence of mediators. The results clearly demonstrated the feasibility to use agar salt bridge for proton transport and role of mediators in MFCs to generate electricity.
    Journal of Environmental Science and Health Part A Toxic/Hazardous Substances & Environmental Engineering 05/2012; 47(6):878-86.
  • S Ziauddin Ahammad, James Gomes, T R Sreekrishnan
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    ABSTRACT: Anaerobic degradation of waste involves different classes of microorganisms, and there are different types of interactions among them for substrates, terminal electron acceptors, and so on. A mathematical model is developed based on the mass balance of different substrates, products, and microbes present in the system to study the interaction between methanogens and sulfate-reducing bacteria (SRB). The performance of major microbial consortia present in the system, such as propionate-utilizing acetogens, butyrate-utilizing acetogens, acetoclastic methanogens, hydrogen-utilizing methanogens, and SRB were considered and analyzed in the model. Different substrates consumed and products formed during the process also were considered in the model. The experimental observations and model predictions showed very good prediction capabilities of the model. Model prediction was validated statistically. It was observed that the model-predicted values matched the experimental data very closely, with an average error of 3.9%.
    Water Environment Research 09/2011; 83(9):791-801. · 1.13 Impact Factor