Bioelectrochemical approaches for removal of sulfate, hydrocarbon and salinity from produced water.

Produced water (PW) is the largest liquid waste stream generated during the exploration and drilling process of both the conventional hydrocarbon based resources like crude oil and natural gas, as well as the new fossil resources like shale gas and coal bed methane. Resource management, efficient utilization of the water resources, and water purification protocols are the conventionally used treatment methods applied to either treat or utilize the generated PW. This review provides a comprehensive overview of these conventional PW treatment strategies with special emphasises on electrochemical treatment. Key considerations associated with these approaches for efficient treatment of PW are also discussed. After a thorough assessment of the salient features of these treatment platforms, we propose a new strategy of uniquely integrating bioelectrochemical processes with biological system for more effective PW treatment and management.

Electrochemical removal of sulfate from petroleum produced water.

Petroleum produced water (PPW) is a waste-stream that entails huge cost on the petroleum industry. Along with other suspended and dissolved solids, it contains sulfate, which is a major hurdle for its alternative use intended toward enhanced oil recovery. This study proposes a two-step process for sulfate removal from PPW. A synthetic PPW was designed for the study using response surface methodology. During the first step, sulfate present in PPW was reduced to sulfide by anaerobic fermentation with 80% efficiency. In the second step, more than 70% of the accumulated sulfide was electrochemically oxidized. This integrated approach successfully removed sulfate from the synthetic wastewater indicating its applicability in the treatment of PPW and its subsequent applications in other oil field operations.

Degradation of sulphonated azo dye Red HE7B by Bacillus sp. and elucidation of degradative pathways.

Bacteria capable of degrading the sulfonated azo dye Red HE7B were isolated from textile mill effluent contaminated soil. The most efficient isolate was identified as Bacillus sp. Azo1 and the isolate could successfully decolorize up to 89% of the dye. The decolorized cultural extract analyzed by HPLC confirmed degradation. Enzymatic analysis showed twofold and fourfold increase in the activity of azoreductase and laccase enzymes, respectively, indicating involvement of both reductive and oxidative enzymes in biodegradation of Red HE7B. Degraded products which were identified by GC/MS analysis included various metabolites like 8-nitroso 1-naphthol, 2-diazonium naphthalene. Mono azo dye intermediate was initially generated from the parent molecule. This mono azo dye was further degraded by the organism, into additional products, depending on the site of cleavage of R-N=N-R molecule. Based on the degradation products identified, three different pathways have been proposed. The mechanism of degradation in two of these pathways is different from that of the previously reported pathway for azo dye degradation. This is the first report of a microbial isolate following multiple pathways for azo dye degradation. Azo dye Red HE7B was observed to be phytotoxic, leading to decrease in root development, shoot length and seedling fresh weight. However, after biotreatment the resulting degradation products were non-phytotoxic.

Influence of headspace composition on product diversity by sulphate reducing bacteria biocathode.

Mixed culture of sulphate reducing bacteria named TERI-MS-003 was used for development of biocathode on activated carbon fabric fastened to stainless steel mesh for conversion of volatile fatty acids to reduced organic compounds under chronoamperometric conditions of -0.85V vs. Ag/AgCl (3.5M KCl). A range of chemicals were bioelectrosynthesized, however the gases present in headspace environment of the bioelectrochemical reactor governed the product profile. Succinate, ethanol, hydrogen, glycerol and propionate were observed to be the predominant products when the reactor was hermetically sealed. On the other hand, acetone, propionate, isopropanol, propanol, isobutyrate, isovalerate and heptanoate were the predominant products when the reactor was continuously sparged with nitrogen. This study highlights the importance of head space composition in order to manoeuvre the final product profile desired during a microbial electro-synthesis operation and the need for simultaneously developing effective separation and recovery strategies from an economical and practical standpoint.

Synthesis, biological activities and SAR studies of novel 1-Ethyl-7-methyl-4-oxo-1,4-dihydro-[1,8]naphthyridine-3-carboxylic acid based diacyl and sulfonyl acyl hydrazines.

BACKGROUND: Diacyl hydrazines have attracted significant interest in medicine, pesticide chemistry and material science. It is an important class of insect growth regulators. In this study, acyl hydrazine, the essential active group was incorporated in to nalidixic acid with the aim of combining the active groups to generate more potent agrochemical. RESULTS: Various nalidixic acid based diacyl and sulphonyl acyl hydrazines derivatives were synthesized and characterized by spectral techniques. These compounds were screened for the antifungal activity against five pathogenic fungi, nitrification inhibitory activity and insect growth regulator (IGR) activity against Spodoptera litura. The fungicidal activity was screened against R. bataticola, S. rolfsii, R. solani, F. oxysporum and A. porri. Most of the compounds showed moderate to good antifungal activity against A. porri (ED50 = 29.6-495.9 µg/mL). All the compounds showed significant nitrification inhibitory activity at 5% level. IGR activity was examined by feeding method against S. litura. CONCLUSION: The study revealed that a few compounds possessed good activity against three different pests namely certain fungus, soil bacteria and insect, among which, compound 37 (R' = 4-chlorophenyl) behaved the best.

Identification of degradation products of thiram in water, soil and plants using LC-MS technique.

In order to evaluate the deleterious effects of exposure to pesticides on a target population, a comprehensive study on their degradation in the various segments of ecosystem under varying environmental conditions is needed. In view of this, a study has been carried out on the metabolic pathways of thiram, a dithiocarbamate fungicide, in a variety of matrices namely water and soil under controlled conditions and plants in field conditions. The identification of degradation products was carried out in samples collected at various time points using LC-MS. The degradation products identified can be rationalized as originating by a variety of processes like hydrolysis, oxidation, N-dealkylation and cyclization. As a result of these processes the presence of some metabolites like dimethyl dithiocarbamate, bis(dimethyl carbamoyl) disulphide, bis(dimethyl dithiocarbamoyl) trisulphide and N-methyl-amino-dithiocarbamoyl sulphide was observed in all the cases. However, some different metabolites were observed with the change in the matrix or its characteristics such as cyclised products 2(N, N-dimethyl amino)thiazoline carboxylic acid and 2-thioxo-4-thiazolidine were observed only in plants. The investigations reflect that degradation initiates with hydrolysis, subsequently oxidation/dealkylation, followed by different types of reactions. The pathways seem to be complex and dependent on the matrices. Dimethyl dithiocarbamate and oxon metabolites, which are more toxic than parent compound, seem to persist for a longer time. Results indicate persistence vis-a-vis toxicity of pesticide and its metabolites and also provide a data bank of metabolites for forensic and epidemiological investigations.

Synthesis of novel nalidixic acid-based 1,3,4-thiadiazole and 1,3,4-oxadiazole derivatives as potent antibacterial agents.

Novel nalidixic acid-based 1,3,4-thia(oxa)diazoles, their thio ethers, sulfones, bis mercapto, and Mannich bases were synthesized and characterized by Infrared spectra, (1) H NMR, (13) C NMR, and elemental analysis. These compounds were evaluated for their antibacterial activity against two Gram-positive and three Gram-negative bacteria. The preliminary bioassay showed that most of the compounds had better antibacterial activity than the parent compounds, 1,3,4-thia(oxa)diazoles, at the dosage 50µg/mL toward five test bacteria. Four Mannich bases of nalidixic acid-based 1,3,4-thiadiazole exhibited maximum antibacterial activity against Bacillus subtilis, Klebsiella pneumoniae, and Pseudomonas aeruginosa with minimum inhibitory concentration in the range of 6.25-125µg/mL.

Effect of organic amendments on microbial activity in chlorpyrifos contaminated soil.

The aim of this research was to study the inhibitory effect of chlorpyrifos (CPF) on soil microbial activity and to evaluate the efficacy of different organic amendments as a biostimulation agent for sustaining the microbial activity and thereby assisting in the remediation of CPF (10 ppm) contaminated soil. Experiments were carried out under controlled conditions (37 °C) up to 74 days; CPF was analyzed by GC-ECD while dehydrogenase activity (DHA) was measured as one of the indices of soil microbial activity. Throughout the experiment, there was higher microbial activity in uncontaminated soil (S) as compared to CPF contaminated soil (SP) and overall a considerably high reduction (63.51%) in average DHA was noticed in CPF contaminated soil. Organic amendments enhanced the microbial activity over unamended CPF contaminated soil. The trend of DHA on 24th day was MS (SP + 1% Mushroom Spent) >VC (SP + 1% Vermicompost) >BS (SP + 1% Biogas Slurry) >SP (Soil spiked with 10 ppm CPF) >FM (SP + 1% Farmyard Manure). The enhancement in pesticide dissipation over the unamended soil showed the following trend VC (37%)>MS (24%) >FM (1.9%). In spite of sufficient DHA, BS could not enhance pesticide dissipation over the unamended soil (SP). These results indicate the potential of vermicompost and mushroom spent compost as suitable biostimulation agents to sustain the microbial activity in CPF contaminated soil.

Synthesis, antimicrobial evaluation and QSAR analysis of novel nalidixic acid based 1,2,4-triazole derivatives.

Novel nalidixic acid based 1,2,4-triazole derivatives were synthesized and characterized using spectral techniques like (1)H NMR, (13)C NMR, IR and mass spectrometry. All these compounds were screened for antimicrobial activity against five bacteria and two pathogenic fungi. Most of these compounds showed better antimicrobial activity than the parent compound, 4-amino-5-mercapto-1,2,4-triazole. Among all the screened compounds, 3-{6-(2-chlorophenyl)-1,2,4-triazolo [3,4-b] [1,3,4]thiadiazol-3-yl}-1-ethyl-7-methyl-1,8-naphthyridin-4(1H)-one (23) was emerged as promising antimicrobial agent (MIC = 16 µg/mL). Quantitative structure activity relationship (QSAR) analysis was carried out using various distance-based topological indices, steric and hydrophobic parameters. Based on the QSAR analysis it is indicative that lipophilic and steric parameters are the pre-requisites for these molecules to act as potent antimicrobial agents.

Decay profile and metabolic pathways of quinalphos in water, soil and plants.

The widespread occurrence of pesticide residues in different agricultural and food commodities has raised concern among the environmentalists and food chemists. In order to keep a proper track of these materials, studies on their decay profiles in the various segments of ecosystem under varying environmental conditions are needed. In view of this, the metabolites of quinalphos in water and soil under controlled conditions and in plants, namely tomato and radish in field conditions have been analysed and possible pathways suggested. In order to follow the decay of the pesticide, an HPLC procedure has been developed. Studies conducted in water at different temperatures, pH and organic content reveal that the persistence of the pesticide decreases with the increase in all the three variables. In the three different types of soils studied, the effect of pH is more or less apparent on a similar line. On an average a faster decay is observed in the case of plants than in water and soil. The decay profiles in all these cases follow first order kinetics. The metabolites were identified by GC-MS. The investigations reflect that degradation occurs through hydrolysis, S-oxidation, dealkylation and thiono-thiol rearrangement. The pathways seem to be complex and different metabolites were observed with the change in the matrix. Quinalphos oxon, O-ethyl-O-quinoxalin-2-yl phosphoric acid, 2-hydroxy quinoxaline and quinoxaline-2-thiol were observed in all the matrices. Results further indicate that the metabolites, 2-hydroxy quinoxaline and oxon, which are more toxic than parent compound, persist for a longer time.

Isolation, characterization and antifungal activity of major constituents of the Himalayan lichen Parmelia reticulata Tayl.

Antifungal activity of hexane, ethyl acetate and methanol extracts of Parmelia reticulata was evaluated against soilborne pathogenic fungi, namely, Sclerotium rolfsii, Rhizoctonia solani, R. bataticola, Fusarium udum, Pythium aphanidermatum and P. debaryanum by poisoned food technique. Maximum antifungal activity was exhibited by hexane and ethyl acetate extracts against most of the test pathogens. Secondary metabolites, namely, (±)-isousnic acid, (±)-protolichesterinic acid, atranorin, evernyl, ethyl hematommate, ethyl orsellinate, methyl hematommate (3-formyl-2,4-dihydroxy-6-methylbenzoic acid methyl ester), 2-hydroxy-4-methoxy-3,6-dimethylbenzoic acid, 1-hydroxy-3,6-dimethoxy-8-methyl-xanthen-9-one, baeomycesic acid and salazinic acid, were isolated from the above extracts and identified by 1H NMR, 13C NMR and mass spectroscopic methods. When these metabolites were tested for antifungal activity against test pathogens, maximum antifungal activity was exhibited by (±)-protolichesterinic acid against R. solani (ED50=23.09 µg mL(-1)) and P. debaryanum (ED50=16.07 µg mL(-1)) and by atranorin against S. rolfsii (ED50=39.70 µg mL(-1)). The antifungal activity of protolichesterinic acid was found to be comparable to that of hexaconazole, a commercial fungicide.

Persistence of azoxystrobin in/on grapes and soil in different grapes growing areas of India.

Persistence of azoxystrobin was studied in/on grapes when applied @ 150 g ai ha⁻¹ (recommended dose) and 300 g ai ha⁻¹ (double the recommended dose) in three grapes growing states of India, namely Karnataka, Maharashtra and Tamil Nadu, in the year 2006-2007. A total of five sprays were given at an interval of about 15 days. Grapes and soil samples were collected after 5th spray, extracted and analysed by gas chromatography using electron capture detector. Half life of azoxystrobin on grapes varied from 5.4 to 11.2 days. Residues of azoxystrobin were much below the prescribed MRL (0.5 mg kg⁻¹) after 21 days. The dissipation of azoxystrobin in soil followed first order rate kinetics with an average half life of 8.1 days at the recommended dose of application.

Physiological studies on endorhizospheric establishment of Azotobacter chroococcum in wheat.

Ten strains of Azotobacter chroococcum were studied for their ability to invade the endorhizosphere of wheat. Strain W-5 exhibited ability to invade endorhizosphere as shown in the microscopic observations. This strain was compared with the strain OA-3 which did not invade the endorhizosphere zone. Strain W-5 showed higher production of cellulase and pectinase than OA-3. Both the strains induced defense enzymes in the host plant. However, induction of peroxidase and phenylalanine ammonia lyase activities (PAL) was higher in OA-3 than W-5. Quantitative differences in flavonoid like compounds obtained from root extracts and root exudates of plants inoculated with these strains were observed.

Metabolism of 14C-azoxystrobin in water at different pH.

Metabolism of (14)C-azoxystrobin was studied in water at pH 4, 7 and 9. The study suggested that volatilization losses of azoxystrobin were very low (3%) during 130 days of incubation. Only 2.5-4.2% of azoxystrobin was mineralised to CO(2) and pH of water did not have much effect on rate of mineralisation. The dissipation of azoxystrobin in water of all the three pHs followed first order kinetic with half-life values ranging from 143 to 158 d; degradation was the fastest at pH 9. Azoxystrobin acid, a major metabolite, was detected 4-7 day onwards and its concentration increased up to 130 days. The formation of azoxystrobin acid was more and faster under alkaline (pH 9) condition than neutral (pH 7) or acidic (pH 4) conditions.

Synthesis of nalidixic acid based hydrazones as novel pesticides.

Thirty-one substituted hydrazones of nalidixic acid hydrazide were synthesized and characterized by spectral techniques. These compounds were evaluated for various biological activities, namely, fungicidal, insecticidal, and nitrification inhibitory activities. The antifungal activity was evaluated against five pathogenic fungi, namely, Rhizoctonia bataticola , Sclerotium rolfsii , Rhizoctonia solani , Fusarium oxysporum , and Alternaria porii . They showed maximum inihibition against A. porii with ED(50) = 34.2-151.3 microg/mL. The activity was comparable to that of a commercial fungicide, hexaconazole (ED(50) = 25.4 microg/mL). They were also screened for insecticidal activity against third-instar larvae of Spodoptera litura and adults of Callosobruchus maculatus and Tribollium castaneum . Most of them showed 70-100% mortality against S. litura through feeding method at 0.1% dose. These compounds were not found to be effective nitrification inhibitors.

Influence of endosulfan on microbial biomass and soil enzymatic activities of a tropical alfisol.

The effect of endosulfan at normal residue level (1 and 10 ppm) and elevated level (100 ppm) on microbial biomass and enzymatic activities of a tropical alfisol was studied. Dehydrogenase, Fluorescein diacetate hydrolase, acid phosphatase, aryl sulphatase activities and microbial biomass of the soil increased by 2.4, 1.7, 1.4, 1.8 and 3.7 times, respectively by the 14th day of incubation with 1 ppm endosulfan, indicating the possible involvement of soil microorganisms and their enzymes in degradation of endosulfan. Soil nitrogenase activity decreased by 8.0 times by the 14th day of application of 1 ppm endosulfan, suggesting that endosulfan or its metabolites may pose toxicological threat to nitrogen fixers in soil.

Antifungal activity of 4'-(2,6,6-Trimethyl-2-cyclohexen-1-yl)-3'-butene-2'-ketoxime N-O-alkyl ethers.

A number of 4'-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3'-butene-2'-ketoxime N-O-alkyl ethers were prepared, separated into their E and Z isomers, and characterized on the basis of (1)H NMR and mass spectroscopy. These compounds were tested in vitro for antifungal activity against four important phytopathogenic fungi, namely, Sclerotium rolfsii , Rhizoctonia bataticola , Macrophomina phaseolina , and Sclerotinia sclerotiorum . E isomers of 4'-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3'-butene-2'-ketoxime N-O-propyl ether (ED(50) = 32.36 microg mL(-1)) and 4'-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3'-butene-2'-ketoxime N-O-(1''-methyl) ethyl ether (ED(50) = 35.50 microg mL(-1)) showed maximum antifungal activity against R. bataticola and S. rolfsii, respectively, whereas 4'-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3'-butene-2'(Z)-ketoxime N-O-pentyl ether was found to be active against M. phaseolina (ED(50) = 31.08 microg mL(-1)) and S. sclerotiorum (ED(50) 21.39 microg mL(-1)), respectively. The Z isomer of 4'-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3'-butene-2'-ketoxime N-O-pentyl ether, which was found to be most effective, was tested against S. sclerotiorum in a greenhouse at 1 and 5% concentrations. The 5% aqueous emulsion of 4'-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3'-butene-2'(Z)-ketoxime N-O-pentyl ether suppressed disease development in pea by 90-95% as compared with the untreated infested soil in the greenhouse after 21 days of treatment.

Schiff bases as potential fungicides and nitrification inhibitors.

A number of substituted Schiff bases were synthesized and characterized by (1)H NMR and mass spectrometry. These compounds were screened for antifungal activity in vitro against pathogenic fungi, namely, Sclerotium rolfsii and Rhizoctonia bataticola, and for their effect on nitrification inhibition under laboratory conditions. Maximum antifungal activity was exhibited by (2,4-dichlorobenzylidene)-(2,4,5-trichlorophenyl)-amine and (3-nitrobenzylidene)-(2,4,5-trichlorophenyl)-amine against both fungi (ED(50) with range from 3 to 24 microg/mL). Maximum nitrification inhibition (NI) was exhibited by (2,4-dichlorobenzylidene)-(2-fluorophenyl)-amine, (4-fluorophenyl)-(3-nitrobenzylidene)-amine, (2,6-dichlorobenzylidene)-(4-fluorophenyl)-amine, and (2,6-dichlorobenzylidene)-(3 fluorophenyl)-amine (NI in the range 91-96%).

Enrichment, isolation and characterization of pentachlorophenol degrading bacterium Acinetobacter sp. ISTPCP-3 from effluent discharge site.

Three pentachlorophenol (PCP) degrading bacterial strains were isolated from sediment core of pulp and paper mill effluent discharge site. The strains were continuously enriched in mineral salts medium supplemented with PCP as sole source of carbon and energy. One of the acclimated strains with relatively high PCP degradation capability was selected and characterized in this study. Based on morphology, biochemical tests, 16S rDNA sequence analysis and phylogenetic characteristics, the strains showed greatest similarity with Acinetobacter spp. The strain was identified as Acinetobacter sp. ISTPCP-3. The physiological characteristics and optimum growth conditions of the bacterial strain were investigated. The results of optimum growth temperature revealed that it was a mesophile. The optimum growth temperature for the strain was 30 degrees C. The preferential initial pH for the strain was ranging at 6.5-7.5, the optimum pH was 7. The bacterium was able to tolerate and degrade PCP up to a concentration of 200 mg/l. Increase in PCP concentration had a negative effect on biodegradation rate and PCP concentration above 250 mg/l was inhibitory to its growth. Acinetobacter sp. ISTPCP-3 was able to utilize PCP through an oxidative route with ortho ring-cleavage with the formation of 2,3,5,6-tetrachlorohydroquinone and 2-chloro-1,4-benzenediol, identified using gas chromatograph-mass spectrometric (GC-MS) analysis. The degradation pathway followed by isolated bacterium is different from previously characterized pathway.

Enrichment and isolation of endosulfan-degrading microorganism from tropical acid soil.

Endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,3,4-benzo-dioxathiepin-3-oxide) is a cyclodiene organochlorine currently used as an insecticide all over the world and its residues are posing a serious environmental threat. This study reports the enrichment and isolation of a microbial culture capable of degrading endosulfan with minimal production of endosulfan sulfate, the toxic metabolite of endosulfan, from tropical acid soil. Enrichment was achieved by using the insecticide as sole sulfur source. The enriched microbial culture, SKL-1, later identified as Pseudomonas aeruginosa, degraded up to 50.25 and 69.77 % of alpha and beta endosulfan, respectively in 20 days. Percentage of bioformation of endosulfan sulfate to total formation was 2.12% by the 20th day of incubation. Degradation of the insecticide was concomitant with bacterial growth reaching up to an optical density of 600 nm (OD600) 2.34 and aryl sulfatase activity of the broth reaching up to 23.93 microg pNP/mL/hr. The results of this study suggest that this novel strain is a valuable source of potent endosulfan-degrading enzymes for use in enzymatic bioremediation. Further, the increase in aryl sulfatase activity of the broth with the increase in degradation of endosulfan suggests the probable involvement of the enzyme in the transformation of endosulfan to its metabolites.