Exploration of Performance Kinetics and Mechanism of Action of a Potential Novel Bioflocculant BF-VB2 on Clay and Dye Wastewater Flocculation.

This study explores production of an efficient bioflocculant; BF-VB2, by strain Bacillus sp. TERI VB2 and proposes its potential application in wastewater treatment. One milligram of BF-VB2 can effectively flocculate 1980.0 mg ± 5.0 mg of kaolin particles leading to 99.0% ± 0.5% enhancement in flocculation activity and 99.6% ± 1.0% reduction in turbidity; in less time. BF-VB2 when applied for treatment of textile dyeing industrial wastewater revealed reduction in dye color (82.78% ± 3.03%), COD (92.54% ± 0.24%), TSS (73.59% ± 0.71%), and chloride ions (81.90% ± 0.716%). The best-fit kinetic model (for both COD removal, and dye decolorization) was pseudo-first order with regression coefficient of 0.98 and 0.95, and rate constant of 4.33 × 10-2 and 1.83 × 102, respectively. Bridging due to presence of surface charges have been proposed as flocculation mechanism. From results obtained during test-tube studies, flocculation in larger volumes (0.01-5.0 L) was also performed to intend taking up BF-VB2 for in situ industrial wastewater treatment. This eco-friendly polysaccharide bioflocculant had longer shelf-life, stability to pH and temperature, cation-independence, and emerged to be more efficient than other flocculants assessed. This study proposed BF-VB2 as a potential natural flocculant candidate for industrial application.

Characterization of a Novel Polymeric Bioflocculant Produced from Bacterial Utilization of n-Hexadecane and Its Application in Removal of Heavy Metals.

A novel polymeric bioflocculant was produced by a bacterium utilizing degradation of n-hexadecane as the energy source. The bioflocculant was produced with a bioflocculating activity of 87.8%. The hydrocarbon degradation was confirmed by gas chromatography-mass spectrometry analysis and was further supported with contact angle measurements for the changes in hydrophobic nature of the culture medium. A specific aerobic degradation pathway followed by the bacterium during the bioflocculant production and hydrocarbon utilization process has been proposed. FT-IR, SEM-EDX, LC/MS, and 1H NMR measurements indicated the presence of carbohydrates and proteins as the major components of the bioflocculant. The bioflocculant was characterized for its carbohydrate monomer constituents and its practical applicability was established for removing the heavy metals (Ni2+, Zn2+, Cd2+, Cu2+, and Pb2+) from aqueous solutions at concentrations of 1-50 mg L-1. The highest activity of the bioflocculant was observed with Ni2+ with 79.29 ± 0.12% bioflocculation efficiency.

Purification and characterization of exopolysaccharide bioflocculant produced by heavy metal resistant Achromobacter xylosoxidans.

Optimization of process parameters enhanced bioflocculating activity of 'Achromobacter xylosoxidans strain TERI L1' from 75% to 83.3% in absence of heavy metals, which decreased to 73% in presence of multi-metals. 'TERI L1' could adsorb 90% of multi-metals when grown in presence of 1250 mg L(-1) Zn, 2 mg L(-1) Cd, 30 mg L(-1) Pb, 200 mg L(-1) Ni and 90 mg L(-1) Cu and could adsorb 1100 mg L(-1) of Pb when grown in presence of 1500 ppm lead nitrate. The bioflocculant was purified and characterized. Bioflocculant yield was 5 g L(-1). Fourier transform infrared spectrum indicated presence of carboxyl, hydroxyl, amino groups, typical of glycoprotein. Spectroscopic analysis of bioflocculant by nuclear magnetic resonance revealed that it is a glycoprotein. LC-MS analysis confirmed the bioflocculant as a carbohydrate hetero polymer. Bioflocculant was composed of 75% total sugar with 72.9% neutral sugar and 11.5% protein. Scanning Electron Micrography revealed effective flocculation of kaolin clay by purified exopolysaccharide bioflocculant.

Bioleaching of nickel from spent petroleum catalyst using Acidithiobacillus thiooxidans DSM- 11478.

The present work deals with optimization of culture conditions and process parameters for bioleaching of spent petroleum catalyst collected from a petroleum refinery. The efficacy of Ni bioleaching from spent petroleum catalyst was determined using pure culture of Acidithiobacillus thiooxidans DSM- 11478. The culture conditions of pH, temperature and headspace volume to media volume ratio were optimized. EDX analysis was done to confirm the presence of Ni in the spent catalyst after roasting it to decoke its surface. The optimum temperature for A. thiooxidans DSM-11478 growth was found to be 32 degrees C. The enhanced recovery of nickel at very low pH was attributed to the higher acidic strength of sulfuric acid produced in the culture medium by the bacterium. During the bioleaching process, 89% of the Ni present in the catalyst waste could be successfully recovered in optimized conditions. This environment friendly bioleaching process proved efficient than the chemical method. Taking leads from the lab scale results, bioleaching in larger volumes (1, 5 and 10 L) was also performed to provide guidelines for taking up this technology for in situ industrial waste management.

Bioflocculant production and biosorption of zinc and lead by a novel bacterial species, Achromobacter sp. TERI-IASST N, isolated from oil refinery waste.

A bioflocculant-producing bacterial isolate designated as 'TERI-IASST N' was isolated from activated sludge samples collected from an oil refinery. This isolate demonstrated maximum bioflocculation activity (74%) from glucose among 15 different bioflocculant-producing bacterial strains isolated from the sludge samples and identified as Achromobacter sp. based on 16S rRNA gene sequence. Optimization of pH and supplementation of urea as nitrogen source in the production medium enhanced the flocculation activity of strain TERI-IASST N to 84% (at pH 6). This strain revealed maximum flocculation activity (90%) from sucrose compared to the flocculation activity observed from other carbon sources as investigated (glucose, lactose, fructose, maltose and starch). Ca(2+) served as the suitable divalent cation for maximum bioflocculation activity of TERI-IASST strain N. Maximum flocculation activity was observed at optimum C/N ratio of 1. Flocculation activity of this strain decreased to 75% in the presence of heavy metals; Zn, Pb, Ni, Cu and Cd. In addition strain N revealed considerable biosorption of Zn (430mgL(-1)) and Pb (30mgL(-1)). Bioflocculant yield of strain N was 10.5gL(-1). Fourier transform infrared spectrum indicated the presence of carboxyl, hydroxyl, and amino groups, typical of glycoprotein. Spectroscopic analysis of bioflocculant by nuclear magnetic resonance revealed that it is a glycoprotein, consisting of 57% total sugar and 13% protein.