Efficacy of natural biocide on control of microbial induced corrosion in oil pipelines mediated by Desulfovibrio vulgaris and Desulfovibrio gigas

We compared the efficacy of a natural biocide with four chemical tetrakishydroxymethyl phosphonium sulfonate, benzyl trimethyl ammonium chloride, and formaldehyde, glutaraldehyde, to control microbial induced corrosion in oil pipelines. The efficacy of biocides were monitored against Desulfovibrio vulgaris and Desulfovibrio gigas in experimental pipes by measuring cell counts, H2S production, Fe(II) production, production of extracellular polymeric substances and structure of biofilm. The treatment with cow urine had minimum planktonic cell counts of 3 102 CFU/mL as well as biofilm cell counts of 9 101 CFU/mL as compared with tetrakishydroxyl methyl phosphonium sulfonate, benzyl trimethyl ammonium chloride, formaldehyde and glutaraldehyde. Sulfide production was the lowest with cow urine (0.08 mmol/L), followed by tetrakishydroxymethyl phosphonium sulfonate 0.72 mmol/L. On day 90 of treatment, Fe(II) production was also found to be the lowest with cow urine. The scanning electron microscopic studies indicated that the biofilm bacteria were killed by cow urine. These results demonstrate the cow urine mediated control of microbially induced corrosion, and this is indicative of its potential as a viable substitute of toxic biocides. To the best of our knowledge, this seems to be the first report which screens possible biocidal activity by cow urine as compared to the most common biocides which oil industry is currently using.     

Decolorization of triphenylmethane dye-bath effluent in an integrated two-stage anaerobic reactor

In the present study, decolorization of a simulated dye waste containing three different triphenylmethane (TPM) dyes--Magenta, Malachite Green and Crystal Violet, was investigated in a laboratory scale, two-stage anaerobic high-rate reactor. The effect of various parameters (influent dye concentration, hydraulic and co-substrate loading rates) on color and COD removal efficiency of the reactor has been studied. It has been shown that the influent dye concentration had little effect on overall COD and color removal efficiency. More than 99% color removal and 96% COD removal efficiency were maintained even at a dye concentration of 500 mg/l and a dye loading rate of 1000 mg/l day. However, a minimum level of glucose as supplementary carbon source is required to maintain the maximum color removal efficiency and it drops appreciably when no glucose is added to the influent. The study also showed that the acidogenic phase of the reaction plays an important role in decolorization of the TPM dyes. In addition, the two-stage anaerobic reactor was observed to have distinct advantages over the single-stage system, as the drop in color and COD removal efficiency of stage 1 are adequately compensated by stage 2 of the reactor especially under high dye loading rates accompanied by low co-substrate loading and under reduced HRTs.     

Phytotoxicity assessment of phenanthrene and pyrene in soil using two barley genotypes

This study investigated the toxicity extent of phenanthrene and pyrene to two cultivars (CM-72 and Gairdner) of barley (Hordeum vulgare). Germination of barley seeds was evaluated in 69-d aged soil, separately spiked with phenanthrene at extractable concentrations of 0.95, 6.3, 59, and 300 mg kg^?1 (dry soil) and pyrene at 1.0, 9.0, 73, and 400 mg kg^?1 (dry soil). Although germination was not inhibited, significant (P < 0.05) reduction in root and shoot length occurred at concentrations of phenanthrene ≥6.3 mg kg^?1 and pyrene ≥9.0 mg kg^?1 after both 72 and 240 h. Fresh and dry biomass of both cultivars reduced with increasing concentrations of both polycyclic aromatic hydrocarbons (PAHs). Barley cultivar CM-72 was more sensitive than Gairdner, and it can be considered suitable for toxicity assessment of PAH-contaminated soils.     

Surfactant enhanced pyrene degradation in the rhizosphere of tall fescue (Festuca arundinacea)

Environmental Science and Pollution Research - The present study was conducted to evaluate the effect of two non ionic surfactants (Tween 80 and Triton X-100), a biosurfactant (Lecithin), and...     

Assessment of phenanthrene bioavailability in aged and unaged soils by mild extraction

It has become apparent that the threat of an organic pollutant in soil is directly related to its bioavailable fraction and that the use of total contaminant concentrations as a measure of potential contaminant exposure to plants or soil organisms is inappropriate. In light of this, non-exhaustive extraction techniques are being investigated to assess their appropriateness in determining bioavailability. To find a suitable and rapid extraction method to predict phenanthrene bioavailability, multiple extraction techniques (i.e., mild hydroxypropyl-β-cyclodextrin (HPCD) and organic solvents extraction) were investigated in soil spiked to a range of phenanthrene levels (i.e., 1.12, 8.52, 73, 136, and 335 μg g^− 1 dry soil). The bioaccumulation of phenanthrene in earthworm (Eisenia fetida) was used as the reference system for bioavailability. Correlation results for phenanthrene suggested that mild HPCD extraction was a better method to predict bioavailability of phenanthrene in soil compared with organic solvents extraction. Aged (i.e., 150 days) and fresh (i.e., 0 day) soil samples were used to evaluate the extraction efficiency and the effect of soil contact time on the availability of phenanthrene. The percentage of phenanthrene accumulated by earthworms and percent recoveries by mild extractants changed significantly with aging time. Thus, aging significantly reduced the earthworm uptake and chemical extractability of phenanthrene. In general, among organic extractants, methanol showed recoveries comparable to those of mild HPCD for both aged and unaged soil matrices. Hence, this extractant can be suitable after HPCD to evaluate risk of contaminated soils.