Isolation, identification and application of novel bacterial consortium TJ-1 for the decolourization of structurally different azo dyes.

A novel bacterial consortium (TJ-1), which could decolorize Acid Orange 7 (AO7) and manyother azo dyes, was developed. In TJ-1 three bacterial strains were identified as Aeromonas caviae, Proteus mirabilis and Rhodococcus globerulus by 16S rRNA gene sequence analysis. AO7 decolorization was significantly higher with the use of consortium as compared to the use of individual strains, indicating complementary interactions among these strains. AO7 decolorization was observed under microaerophilic condition in the presence of organic carbon source. Either yeast extract (YE) alone or a combination of YE and glucose resulted in much higher decolorization of AO7 as compared to glucose alone, peptone or starch. Kinetic studies with different initial AO7 concentrations showed that more than 90% decolorization could be achieved even at 200mg/l within 16h. Fed-batch studies showed that AO7 decolorization required 10h during the first cycle and 5h in the second and third cycles, showing that bacterial cells could be used for multiple cycles. The consortium also decolorized fifteen other azo dyes individually as well as a simulated wastewater containing a mixture of all the sixteen azo dyes, thus, conferring the possibility of application of TJ-1 for the treatment of industrial wastewaters.

Contamination of nitrate and fluoride in ground water along the Ganges Alluvial Plain of Kanpur district, Uttar Pradesh, India.

Nitrate-N and Fluoride concentrations were analyzed in shallow and unconfined ground water aquifers of Kanpur district along the Ganges Alluvial Plain of Northern India. Kanpur district was divided into three zones namely, Bithore, Kanpur City and Beyond Jajmau and sampling was carried out three seasons (summer, monsoon and winter). The data set consisted of the results of water samples from around 99 India Mark II hand Pumps, which were analyzed for summer monsoon and winter seasons. In Bithore zone, 19% of the samples exceeded the BIS (Bureau of India Standards) limit 10.2 mg/l as nitrate-N and as high as 166 mg/l as nitrate-N was observed. 10% and 7% samples in Kanpur city and beyond Jajmau zone respectively, exceeded the BIS limit. The Frequency distribution histogram of nitrate-N revealed a skewed (non-normal) distribution. Both point and non-point sources contribute to the ground water contamination. Especially in Bithore zone, the point sources could be attributed to the animal wastes derived from cows and buffaloes and non point sources could be due to the extensive agricultural activity prevalent in that area. Fluoride concentration in most samples was within the BIS maximum permissible level of 1.5 mg/l. No significant seasonal variation in water quality parameters was observed.

Investigations on activated alumina based domestic defluoridation units.

Investigations were carried out on the defluoridation of fluoride-spiked ground water in domestic defluoridation units (DDU) with activated alumina (AA). Specific safe water yield (SSY) was determined as a function of AA amount and adsorbent depth. Reuse potential of exhausted AA was assessed by regenerating and reusing AA in multiple defluoridation cycles. High fluoride uptake capacity (FUC) from ground water matrix as well as retaining approximately 95% FUC up to five cycles showed the suitability of AA for defluoridation in DDU. SSY, liters of safe water/kg AA, was dependent on the AA amount and its depth. There was a significant decrease in SSY with the decrease in AA depth in different DDUs, even though the amount was maintained constant. The derived data from four DDUs, with 3-5 kg AA and depth ranging from 5 to 13 cm, showed that DDU design is one of the most important parameter to be considered for optimizing SSY.

Decolorization and partial degradation of monoazo dyes in sequential fixed-film anaerobic batch reactor (SFABR).

Decolorization of two monoazo dyes, acid orange 6 (AO6) and acid orange 7 (AO7), were studied in sequential fixed-film anaerobic batch reactor (SFABR) with varying dye concentrations and 500 mg/L glucose as the co-substrate. More than 90% dye decolorization could be achieved, even at 300 mg/L, with both AO6 and AO7 and dye decolorization rates were 168 mg/L/d and 176 mg/L/d, respectively. COD removals with these two monoazo dyes were significantly different, as 75% and 35% decrease were observed with AO6 and AO7, respectively. UV-visible spectral as well as HPLC analysis of SFABR treated effluent showed the accumulation of 4-aminobenzenesulfonate (4-ABS) from AO6 and AO7. Aminoresorcinol (AR) formed from AO6 decolorization could not be detected at the end of SFABR cycle. This along with high COD removal indicated its further degradation. Formation of pink coloration on exposure to air indicated the presence of 1-amino-2-naphthol (AN) in AO7 fed reactor effluent. Thus both 4-ABS and AN were resistant to further degradation under anaerobic conditions. Presence of nitrate did not decrease the observed decolorization at the end of 24h SFABR cycle, although initial rate was decreased. This indicates the suitability of SFABR configuration for the treatment of azo-dye containing wastewaters in the presence of nitrate.

Mineralization of 4-aminobenzenesulfonate (4-ABS) by Agrobacterium sp. strain PNS-1.

A bacterial strain, PNS-1, isolated from activated sludge, could utilize sulphanilic acid (4-ABS) as the sole organic carbon and energy source under aerobic conditions. Determination and comparison of 16S r DNA sequences showed that the strain PNS-1 is closely related to the species of Agrobacterium genus. Growth on 4-ABS was accompanied with ammonia and sulfate release. TOC results showed complete mineralization of sulphanilic acid. This strain was highly specific for 4-ABS as none of the sulphonated aromatics used in the present study including other ABS isomers were utilized. Strain PNS-1 could, however, utilize all the tested monocyclic aromatic compounds devoid of a sulfonate group. No intermediates could be detected either in the growth phase or with dense cell suspensions. Presence of chloramphenicol completely inhibited 4-ABS degradation by cells pregrown on succinate, indicating that degradation enzymes are inducible. No plasmid could be detected in the Agrobacterium sp. Strain PNS-1 suggesting that 4-ABS degradative genes may be chromosomal encoded.

Degradation of 4-aminobenzenesulfonate by alginate encapsulated cells of Agrobacterium sp. PNS-1.

Studies were carried out on 4-aminobenzenesulfonate (4-ABS) degradation by free and alginate entrapped cells of Agrobacterium sp. PNS-1. Degradation rate in batch reactors with free cells was marginally higher than Ca-encapsulated cells. Comparison of Ca2+ and Ba2+ as gelling agents showed that 4-ABS removal rate was significantly less with Ba-alginate entrapped cells. Specific degradation rates, using linear regression analysis and based on the initial biomass in the beads, varied from 49.7 mg/mg biomass/h to 92.0 mg/mg biomass/h for Ca-alginate encapsulated cells for different initial 4-ABS concentrations ranging from 200 to 800 mg/L. UV spectra of the aliquots drawn at different time intervals from batch reactors did not show accumulation of any intermediate during degradation. Ca-alginate immobilized cells could be repeatedly reused upto five cycles without any loss of activity. Studies with packed bed reactors, operated in a semi-continuous mode, showed that this could be used for 4-ABS degradation.

Removal of hexavalent chromium using a novel cross linked xanthated chitosan.

Suitability of a novel cross linked, chemically modified chitosan as highly efficient adsorbent for the recovery of toxic chromium(VI) was studied. After cross linking with glutaraldehyde, xanthate group was grafted onto the back bone of chitosan. Sorption was found to be both pH and concentration dependent, with pH 3 being the optimum value. Both, chemically modified beads (CMCB) and flakes (CMCF) followed a pseudo-second-order kinetics with a rate constant of 2.037 and 4.639 g/mg/min, respectively. The equilibrium data followed the Langmuir isotherm model with maximum capacities of 625 mg/g and 256.4 mg/g and for CMCF and CMCB respectively. Desorption studies revealed the reusability of the sorbent for at least 10 cycles without any significant change in adsorption capacities.

Anoxic treatment of phenolic wastewater in sequencing batch reactor.

Studies were conducted on the anoxic phenol removal using granular denitrifying sludge in sequencing batch reactor at different cycle lengths and influent phenol concentrations. Results showed that removal exceeded 80% up to an influent phenol concentration of 1050 mg/l at 6 h cycle length, which corresponded to 6.4 kg COD/m3/d. Beyond this, there was a steep decrease in phenol and COD removal efficiencies. This was accompanied by an increase in nitrite concentration in the effluent. On an average, 1 g nitrate-N was consumed per 3.4 g phenol COD removal. Fraction of COD available for sludge growth was calculated to be 11%.

Chemical modification of specific active site amino acid residues of Enterobacter aerogenes glycerol dehydrogenase.

Enterobacter aerogenes glycerol dehydrogenase (G1DH EC 1.1.1.6), a tetrameric NAD+ specific enzyme catalysing the interconversion of glycerol and dihydroxyacetone, was inactivated on reaction with pyridoxal 5-phosphate (PLP) and o-phthalaldehyde (OPA). Fluorescence spectra of PLP-modified, sodium borohydride-reduced G1DH indicated the specific modification of epsilon-amino groups of lysine residues. The extent of inhibition was concentration and time dependent. NAD+ and NADH provided complete protection against enzyme inactivation by PLP, indicating the reactive lysine is at or near the coenzyme binding site. Modification of G1DH by the bifunctional reagent OPA, which reacts specifically with proximal epsilon-NH2 group of lysines and -SH group of cysteines to form thioisoindole derivatives, inactivated the enzyme. Molecular weight determinations of the modified enzyme indicated the formation of intramolecular thioisoindole formation. Glycerol partially protected the enzyme against OPA inactivation, whereas NAD+ was ineffective. These results show that the lysine involved in the OPA reaction is different from the PLP-reactive lysine, which is at or near the coenzyme binding site. DTNB titration showed the presence of only a single cysteine residue per monomer of G1DH. This could be participating with a proximal lysine residue to form a thioisoindole derivative observed as a result of OPA modification.