N. Arul Manikandan

Waste Litchi Peels for Cr(VI) Removal from Synthetic Wastewater in Batch and Continuous Systems: Sorbent Characterization, Regeneration and Reuse Study

AbstractCr(VI) removal was investigated under batch and continuous mode using dry Litchi chinensis as the low-cost sorbent. Batch biosorption experiments displayed a maximum Cr(VI) removal of 99% with litchi peels, suggesting that the litchi peels can be utilized as a prime sorbent for removal of Cr(VI). Fourier transform infrared spectroscopy (FTIR) profiles confirmed the occurrence of ─NH, ─CH, ─CH3, ─CH2, and C═O functional groups in the litchi peels for the biosorption of Cr(VI). Cr(VI) sorption thermodynamics by litchi peels indicated that the reaction is endothermic and spontaneous in nature. The effect of various co-ions on Cr(VI) biosorption in the batch experiments revealed a significant effect due to Fe2+(p=0.021) and PO43− (p=0.043) ions on biosorption of Cr(VI). By fitting the experimental data on Cr(VI) biosorption to different sorption isotherm models, a very high coefficient of determination (R2) and very high biosorption capacity values were obtained for the Freundlich model. Cr(VI) sorpti...

A novel biological sulfate reduction method using hydrogenogenic carboxydotrophic mesophilic bacteria.

Sulfate reduction by carbon monoxide (CO) utilizing anaerobic biomass from a large scale upflow anaerobic sludge blanket reactor was studied. Anaerobic mixed microbial consortia from five different sources were initially examined for their biological CO conversion potential. Among the different biomass, the biomass from an upflow anaerobic sludge blanket reactor treating domestic wastewater, located in Kavoor, Karnataka, India, showed a maximum CO conversion efficiency. The effect of three main culture parameters, i.e. inoculum volume, initial CO concentration and temperature on simultaneous CO conversion and sulfate reduction was assessed employing the Taguchi experimental design technique. A maximum CO conversion of 85.62% and a maximum sulfate reduction of 50.65% were achieved. Furthermore, the experimental data was fitted to substrate inhibition models reported in the literature. Among the different models, Monods and Haldane kinetic models were found most suitable to describe the kinetics of biomass growth and CO removal by the anaerobic biomass.

Anthracene Biodegradation by Oleaginous Rhodococcus opacus for Biodiesel Production and Its Characterization

ABSTRACT This study examined biodegradation of anthracene, a model low molecular weight polycyclic aromatic hydrocarbon (PAH) by oleaginous Rhodococcus opacus for biodiesel production. Specific biomass growth rate (µ) in the range of 0.0075–0.0185 h−1 could be attained over the initial anthracene concentration (50–500 mg L−1), along with 68–70.6% (w/w) lipid accumulation. 10% (v/v) inoculum size showed more positive effect than 5% (v/v) inoculum size on both anthracene biodegradation efficiency and lipid accumulation by R. opacus. 1H and 13C nuclear magnetic resonance (NMR) spectroscopy of the bacterial lipids revealed 82.25% saturated fatty acids content. Furthermore, the transesterified bacterial lipids predominantly consisted of methyl palmitate (32.4%) and methyl stearate (25.9%) as the major fatty acid methyl esters (FAMEs). Overall, this study revealed a very good potential of the bacterium for the production of biodiesel from PAH-containing wastewater.

Real-time lipid production and dairy wastewater treatment using Rhodococcus opacus in a bioreactor under fed-batch, continuous and continuous cell recycling modes for potential biodiesel application

ABSTRACT This study focused on lipid production from dairy wastewater using Rhodococcus opacus PD630 in a bioreactor. Simultaneous wastewater COD removal, biomass production and lipid accumulation by R. opacus were evaluated using the bioreactor operated under three different culture modes: fed-batch, continuous and continuous cell recycling. To support the R. opacus growth, the dairy wastewater was supplemented with 25% (v/v) mineral salt media. Results from the fed batch operated bioreactor revealed that a maximum COD removal efficiency of 93% could be achieved along with 1.1 g L-1 of lipid accumulation by the bacteria. Continuous mode experiments provided the best results with almost 100% COD removal efficiency and a maximum lipid accumulation of 1.8 g L-1 at a hydraulic retention time (HRT) of 6.6 h. However, lipid production was even more superior under continuous cell recycle mode with a maximum lipid accumulation of 3.4 g L-1. Thus, the present study proved that R. opacus can be successfully scaled up for efficient dairy wastewater treatment along with lipid accumulation for potential biofuel application.

Kinetics, biochemical and factorial analysis of chromium uptake in a multi-ion system by Tradescantia pallida (Rose) D. R. Hunt

ABSTRACT Discharge of wastewater from electroplating and leather industries is a major concern for the environment due to the presence of toxic Cr6+ and other ions, such as sulfate, nitrate, phosphate, etc. This study evaluated the potential of Tradescantia pallida, a plant species known for its Cr bioaccumulation, for the simultaneous removal of Cr6+, SO42−, NO3−, and PO43−. The effect of different co-ions on Cr6+ removal by T. pallida was examined following the Plackett-Burman design of experiments carried out under batch hydroponics conditions. The results revealed a maximum removal of 84% Cr6+, 87% SO42−, 94% NO3− and 100% PO43− without any phytotoxic effect on the plant for an initial Cr6+ concentration in the range 5–20 mg L−1. SO42− and NO3− enhanced Cr uptake at a high initial Cr concentration (20 mg L−1), whereas PO43− did not affect Cr uptake both at high and low initial Cr concentrations. The Cr6+ removal kinetics in the presence of different ions was well described by the pseudo-second-order kinetic model which revealed that both biosorption and bioaccumulation of the metal played an important role in Cr6+ removal. Increase in the total carbohydrate and protein content of the plant following Cr6+ and co-ions exposure indicated a good tolerance of the plant toward Cr6+ toxicity. Furthermore, enhancement in the lipid peroxidation and catalase activity in T. pallida upon Cr6+ exposure revealed a maximum stress-induced condition in the plant. Overall, this study demonstrated a very good potential of the plant T. pallida for Cr6+ removal from wastewater even in the presence of co-ions.