IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Biodegradation studies were carried out in aerobic batch systems using Benzene, Toluene and Xylene (BTX) as the sole carbon source to evaluate the versatility of a bacterial consortium taken from a domestic sewage treatment plant. This mixed microbial culture was acclimatized using individual BTX compounds and the potential capability of microbes precultured on a single substrate to degrade other compounds was studied over a wide range of BTX concentrations (∼50-500mg/L). The biodegradation pattern and growth rates ascertained experimentally in these versatility studies were compared with results obtained from individual degradation experiments studied earlier. Similar growth pattern was observed for all the substrate with inhibition occurring at higher concentrations (∼200 mg/L for Benzene and Xylene, ∼250mg/L for Toluene). Toluene was degraded more than the other substrates followed by benzene and xylene. Adaptation to a more toxic compound like benzene and xylene improved the utilization of toluene. On the other hand microbes grown on a less toxic compound (toluene), grew at a lower rate in the presence of more toxic compounds. Kinetic parameters such as μmax, K I and KS were determined using the Haldane's and Levenspiel's substrate inhibition models. Results from Haldane's model were more illustrative of the experimental observations and were found to satisfactorily explain the system behavior. © 2005 Springer Science + Business Media, Inc.

Department Of Civil Engineering

GENERAL

Contaminated Soils, Sediments and Water

Substrate versatility studies on the aerobic degradation of BTX compounds

In the present investigation, an attempt was made to develop a treatment system for the management of atrazine bearing wastewater. The system consists of an upflow anaerobic sludge blanket (UASB) reactor followed by an adsorption column using waste activated carbon as the adsorbent. The UASB reactor could remove more than 80% of organic matter and 40-50% of atrazine, irrespective of the concentration of organic matter and atrazine tried. Though low concentration of atrazine did not affect the anaerobic system, higher atrazine concentration in the range of 10-15 mg/ L had a little effect on the treatment system. The adsorption column could remove atrazine from the UASB effluent effectively. Methanol could desorb the atrazine from the adsorbent. The regenerated adsorbent retained 80% of its original capacity. The regenerant can be utilized as a pesticide. © ASCE.

Fulltext

Practice Periodical of Hazardous, Toxic, and Radioactive Waste Management

Management of atrazine bearing wastewater using an upflow anaerobic sludge blanket reactor-adsorption system

A microbial consortium acclimatized with benzene, toluene or xylene (BTX) was employed to study the degradation pattern of these compounds individually under aerobic conditions. Batch and continuous experiments were conducted to evaluate the adaptability of the enriched cultures under substrate versatility conditions. The bio-kinetic parameters obtained under substrate versatility conditions were compared with those of a single substrate condition. Similar degradation patterns were observed for all the substrates with inhibition occurring at higher concentration (∼150 mg/L for benzene and xylene, and ∼200 mg/L for toluene). Toluene degradation was highest, followed by benzene and xylene in the aqueous phase. Adaptation to a more toxic compound like benzene and xylene improved the utilization of toluene. On the other hand, microbes grown on a less toxic compound (toluene) grew at a lower rate in the presence of more toxic compounds. Suitable kinetic parameters such as μmax (maximum specific growth rate per hour), Ks (half saturation constant, mg/L), and KI (threshold substrate inhibition constant, mg/L) were determined using Haldane and Levenspiel substrate inhibition models. The Haldane equation seems to be an adequate expression for the system. The degradation behavior of pollutants in the gas phase was also evaluated using a toluene acclimatized biotrickling filter operated in continuous mode. The biotrickling filter acclimatized with toluene could degrade benzene and xylene with a lower elimination capacity. But, the system could recover its original efficiency quite fast even after a prolonged shock loading. The degradation was better for toluene, followed by benzene and xylene. © 2004 Elsevier B.V. All rights reserved.

Journal of Hazardous Materials

Performance of BTX degraders under substrate versatility conditions

Atrazine degradation by anaerobic mixed culture microorganism in co-metabolic process and in absence of external carbon and nitrogen source was studied at influent atrazine concentration range of 0.5-15mg/l. Wastewater of desired characteristic was prepared by the addition of various constituents in distilled water spiked with atrazine. In co-metabolic process, dextrose of various concentrations (150-2000mg/l) was supplied as external carbon source. The reactors were operated in sequential batch mode in which 20% of treated effluent was replaced by the same amount of fresh wastewater everyday, thus maintaining a hydraulic retention time (HRT) equal to 5 days. In co-metabolic process, 40-50% of influent atrazine degradation was observed. First-order atrazine degradation rate (expressed in day-1) was better in co-metabolic process (5.5×10-4) than in absence of external carbon source (2.5×10-5) or carbon and nitrogen source (1.67×10-5). In presence of 2000mg/l of dextrose, atrazine degradation was between 8% and 15% only. Maximum atrazine degradation was observed from wastewater containing 300mg/l of dextrose and 5mg/l of atrazine. Influent atrazine concentration did not have much effect on the methanogenic bacteria which was clear from methane gas production and specific methanogenic activity (SMA). © 2004 Elsevier Ltd. All rights reserved.

VIT Unitversity

World University root node

Water Research

Atrazine degradation in anaerobic environment by a mixed microbial consortium

Out of an array of bacterial strains isolated from soil contaminated with effluents from electroplating wastewater, Bacillus coagulans exhibited the maximum Cr(VI) reduction potential. The feasibility of an immobilized B. coagulans bioreactor for hexavalent chromium reduction was investigated. Experimental results demonstrated that near complete removal of Cr(VI) was achieved in the reactor with an initial Cr(VI) concentration of 26 mg/l and reactor time of 24 h. The removal efficiency in the bioreactor was significantly affected by the influent Cr(VI) concentration, the Cr(VI) loading rate, the reaction time and the amount of Cr(VI) reduced by the biomass.

International Journal of Environment and Pollution

Immobilised microbial reactor for the biotransformation of hexavalent chromium

Complete treatment of sulfur dioxide (SO2) from flue gases in a two-stage process consisting of a biotrickling filter followed by biological post-treatment unit was investigated. The biotrickling filter could remove 100% of influent S02from simulated flue gas at an empty bed residence time of 6 s for a concentration range of 300-1000 ppmv. All the absorbed SO2 was recovered in the biotrickling filter liquid effluent as sulfite (a product of chemical reaction of SO2) and sulfate (product of biological oxidation of sulfite). The biotrickling filter liquid effluent was further processed biologically in a single post-treatment unit consisting of a combined anaerobic and microaerophilic reactor for the simultaneous reduction of sulfate and sulfite to sulfide and oxidation of sulfide to elemental sulfur. The post-treatment unit could effectively treat the biotrickling filter effluent and produce elemental sulfur. The sulfur production efficiency of the reactor reached about 80% of the SO2 treated. This new biological treatment system seems to be a promising alternative for flue gas desulfurization.

Environmental Science and Technology

Sulfur dioxide treatment from flue gases using a biotrickling filter - Bioreactor system

Performance of an anaerobic reactor in treating atrazine bearing wastewater using a mixed anaerobic microbial culture having high acetoclastic methanogen population was evaluated in batch and semi-continuous mode of operation. At an initial atrazine concentration of 5.0 mg/1, atrazine reduction of 30.2% after 5 days and 64% after 50 days were observed in semi continuous and batch mode of operation respectively. Carbonaceous material removal measured as chemical oxygen demand (COD) was more than 90% in both the cases. Initial COD ws 305±7 mg/1. Experimental results showed that atrazine degradation was better in presence of dextrose than that of sodium acetate. Percentage of methane in biogas was more in acetate fed reactor than dextrose fed reactor.

Sustainable Environmental Sanitation and Water Services: Proceedings of the 28th WEDC Conference

Treatment of atrazine bearing wastewater by mixed methanogenic culture

Performance of mixed microbial anaerobic culture in treating synthetic wastewater with high Chemical Oxygen Demand (COD) and varying atrazine concentration was studied. Performance of hybrid reactors with wood charcoal as adsorbent, with a dose of 10 g/l and 40 g/l, along with the microbial mass was also studied. All the reactors were operated in sequential mode with Hydraulic Retention Time (HRT) of 5 days. In all the cases, COD removal after 5 days was found to be above 81%. Initial COD was above 1000 mg/l. From a hybrid reactor COD removal after 2 days was observed to be 90%. Atrazine reduction after 5 days by microbial mass alone was 43.8%, 40% and 33.2% with an initial concentration of 0.5, 1.0 and 2.0 mg/l respectively. MLSS on all the cases were almost same. Increasing MLSS concentration by about 2 fold did not increase the atrazine removal efficiency significantly. Maximum atrazine removal was observed to be 64% from the hybrid reactor with 10 g/l of wood charcoal and 69.4% from the reactor with 40 g/l of wood charcoal. Atrazine removal from the hybrid reactors after 15 days were observed to be 35.7% and 38.7%, which showed that the higher dose of wood charcoal in hybrid reactor did not improve the atrazine removal efficiency significantly. Specific methanogenic activity test showed no inhibitory effect of atrazine on methane producing bacteria. The performance of anaerobic microorganisms in removing atrazine with no external carbon source and inorganic nitrogen source was studied in batch mode. With an initial concentration of 1.0 mg/l, reduction of atrazine by the anaerobic microorganisms in absence of external carbon source after 35 days was observed to be 61.8% where as in absence of external carbon and inorganic nitrogen source the reduction was only 44.2% after 150 days. Volatilization loss of atrazine was observed to be insignificant.

Journal of Environmental Science and Health - Part B Pesticides, Food Contaminants, and Agricultural Wastes

Anaerobic treatment of atrazine bearing wastewater

Our main objective was to isolate bacteria from soil contaminated with effluents from electroplating wastewater and assess their potential to remove copper from the aqueous phase. The strain identified as Bacillus polymyxa accumulated copper inside the cell, where it bound to the cell wall. The intracellular metal accumulation led to the inhibition of dehydrogenases, which is essential for the energy deriving reactions. Addition of thiol group containing compounds, like reduced glutathione, dithiothreitol and mercaptoethanol, revived the enzyme activity, implicating the sulfhydryl groups as the target of metal action. However, when the cells were exposed to higher concentration of Cu(II), irreversible enzyme denaturation occurred. Desorption with DTT and citrate showed that 82% of the metal was accumulated on cell surface and the contribution from metabolism-dependent intracellular accumulation was only 10-12%. The surface characterization of B. polymyxa indicated the presence of carboxyl, imidazolium, a mino and phenolic groups, which might be responsible for metal uptake. Electron paramagnetic resonance (EPR) spectroscopy studies indicated that the metal coordinating environment could be either CuN2O2 or CuNO3 chromophores, which may be the result of binding of Cu(II) to oxygen atoms of carboxylic groups of cell wall peptidoglycan and nitrogen atoms of amino-sugars or structural proteins. This environment got slightly altered after several treatments of B. polymyxa, leading to the formation of CuO4, suggesting the coordination of copper to four oxygen atoms derived from carboxyl groups of peptidoglycan.

An insight into the mechanism of biosorption of copper by Bacillus polymyxa

In the present study, different grades of indigenously available activated alumina (AA) were screened for their arsenic removal capacity. For both As(III) and As(V), A1 (Grade 1, 0.3-0.6 mm) activated alumina has shown better removal efficiency. The optimum pH for the adsorption phenomena was around 7.0. Chlorine at a dose of 20 mg/l could completely oxidize As(III) to As(V), which also assured the bacteriological quality of the water. Among various anions studied, sulfate seems to have maximum competition with arsenic for adsorption sites. A portable filter with a flow rate of 6 l/h and a contact time of 5 minutes could effectively be used for the treatment of arsenic contaminated water. The exhausted activated alumina could regenerate with 4% NaOH solution without much reduction in efficiency. © 2001 Inderscience Enterprises Ltd.

International Journal of Water

Development of a portable filter for arsenic removal from drinking water

Kinetic studies with Pseudomonas aeruginosa using actinides and lanthanides indicated a two-phase metal uptake. Equilibrium uptake data of all the metals studied could be fitted to Langmuir as well as Freundlich models. The Scatchard plots showed that there were mainly two types of receptor sites on the cell walls of P. aeruginosa having different affinities for the metal ions. EDAX studies revealed replacement of calcium and magnesium ions from biomass by sorbed metal. Around 85% of the adsorbed metal could be released using citrate buffer (pH 4.0, 0.2 M). Metal desorption was as high as 95% with HCl. Continuous flow studies using P. aeruginosa immobilized on activated alumina gave 80% enhancement of lanthanum removal efficiency compared to the control column. Regeneration of the column resulted in 80% of its initial capacity in succeeding cycles. Journal of Industrial Microbiology &amp; Biotechnology (2000) 25, 1–7.

Journal of Industrial Microbiology and Biotechnology

ORIGINAL PAPERS Biosorption of U, La, Pr, Nd, Eu and Dy by Pseudomonas aeruginosa

Copper uptake potential of different bacterial strains isolated from contaminated soil was compared. The bacterial strain identified as Bacillus polymyxa showed maximum copper uptake capacity. An attempt was made to elucidate the site of interaction of Cu(II) with B. polymyxa using electron paramagnetic resonance (EPR) studies. The EPR spectra showed that accumulated copper formed complexes with oxygen and nitrogen which may be the carboxyl groups of cell-wall peptidoglycan and nitrogen atoms of aminosugars or structural proteins. The absence of super hyperfine splitting in the g ⊥ region of EPR spectra of treated B. polymyxa cells after Cu(II) uptake indicated that copper could be coordinated with the oxygen atoms from carboxyl groups of peptidoglycan in the cell walls.Copper uptake potential of different bacterial strains isolated from contaminated soil was compared. The bacterial strain identified as Bacillus polymyxa showed maximum copper uptake capacity. An attempt was made to elucidate the site of interaction of Cu(II) with B. polymyxa using electron paramagnetic resonance (EPR) studies. The EPR spectra showed that accumulated copper formed complexes with oxygen and nitrogen which may be the carboxyl groups of cell-wall peptidoglycan and nitrogen atoms of aminosugars or structural proteins. The absence of super hyperfine splitting in the g is perpendicular to region of EPR spectra of treated B. polymyxa cells after Cu(II) uptake indicated that copper could be coordinated with the oxygen atoms from carboxyl groups of peptidoglycan in the cell walls.

Water, Air, and Soil Pollution

Site of interaction of copper on Bacillus polymyxa

Investigation on Cr(VI) reduction was conducted using bacteria isolated from soil samples receiving electroplating wastewater. Chromium reduction capacity of these isolates was compared with that of Pseudomonas aeruginosa, a pure culture procured from the Institute of Microbial Technology, as well as Bacillus circulans, a laboratory isolate from garden soil. Bacillus coagulans, isolated and identified from chromium polluted soil, gave maximum reduction potential among all organisms studied. Malate was found to yield maximum biotransformation out of four electron donors employed. B. coagulans was able to reduce Cr(VI) even at 10 mM initial Cr(VI) concentration. With an increase in initial cell density, Cr(VI) reduction capacity was also increased; however, maximum specific biotransformation occurred at low cell densities. The optimum pH for Cr(VI) reduction was 7. Sulphates and nitrates did not compete with Cr(VI) for accepting the electrons. The presence of respiratory inhibitors like DNP and NaN3 marginally reduced the Cr(VI) reduction capacity. Cell free extracts were able to reduce Cr(VI) even in the absence of external electron donors; however, marginal increase was found in the presence of malate, nicotinamide adenine dinucleotide, and reduced nicotinamide adenine dinucleotide. The contribution of cell membrane in Cr(VI) reduction was negligible. Hence, the soluble enzymes appear to be responsible for Cr(VI) reduction by B. coagulans.

Journal of Environmental Engineering

Cr(VI) reduction by Bacillus coagulans isolated from contaminated soils

The copper removal potential of Pseudomonas aeruginosa immobilized on different adsorbent resins has been studied. Duolite S-761 was found to be the most suitable matrix for bacterial immobilization. Column studies were conducted using virgin as well as bacteria-immobilized resin. The experimental results reveal that resin with immobilized cells as sorbent increased the column capacity by more than 100%. Sorbed copper (II) could be desorbed using citrate buffer, and the bacteria immobilized reactor could be reused for removal of copper(II) with more than 90% efficiency. Further, the immobilized microbes were found to be viable. Hydrochloric acid (0.1 N) was able to desorb almost 100% of the sorbed metal, but the viability of the cells was affected, as expected.

Immobilized microbial reactor for heavy metal pollution control

The mechanism of accumulation of copper(II) by Pseudomonas aeruginosa was investigated. Uptake consisted of a rapid process (likely to be extracellular binding) followed by a slow phase (possibly cellular uptake). The sorption capacity of the microbe was found to be 50 mg/g, and sorption followed the Langmuir isotherm. The presence of mild mineral acids (0.1 N HCl) led to destructive desorption of 95% of sorbed metal, whereas citrate buffer (pH 4) desorbed 80% of the accumulated metal ions non-destructively. Spectroscopic and microscopic studies indicated the accumulation of metal inside the cell, though the maximum uptake was by the cell wall.

Biosorption of copper(II) by pseudomonas aeruginosa

While studies on the potential of many biosorbents for heavy metal uptake have been reported, the results on scale-up are relatively scanty. Even in those papers where there is a report of reactor performance, more emphasis is given to the metal uptake part and the critical issue of headloss development in columns is not touched upon. This paper presents the results of a scale-up study conducted with an established biosorbent. Ganoderma lucidum, for uptake of rare earth elements. The uptake as well as the reactor characteristics are discussed. © 1994.

Bioresource Technology

Application studies of biosorption for monazite processing industry effluents

The performance evaluation of three pilot scale subsurface flow constructed wetlands (CW), i.e. horizontal flow (HFCW), vertical flow (VFCW) and a baffle type-hybrid (HYCW) was studied. The units were continuously fed with greywater and were planted with Phragmites australis. The inflow concentrations of BOD, COD, TSS, NO3, TP and FC were in the range of 72-120 mg/l, 216-320 mg/l, 224-320 mg/l 10.3-14.6 mg/l, 2.9-3.8 mg/l and 50-120 CFU/100 ml respectively. The average removal efficiencies of BOD, COD, TSS, TP, TN and FC in HYCW were 95 ± 2%, 96 ± 3%, 98 ± 2%, 92 ± 2%, 98 ± 2% and 98 ± 2% respectively and comparatively more than the other two constructed wetlands.