Isolation and characterization of a novel denitrifying bacterium with high nitrate removal: Pseudomonas stutzeri

The aim of this study was to isolate and characterize a high efficiency denitrifier bacterium for reducing nitrate in wastewater. Six denitrifier bacteria with nitrate removal activities were isolated from a petrochemical industry effluent with high salinity and high nitrogen concentrations without treatment. The isolated bacteria were tested for nitrate reomoval activity. One of the bacterium displayed the highest reduction of nitrate. The strain was preliminarily identified using biochemical tests and further identified based on similarity of PCR-16S rRNA using universal primers. Biochemical and molecular experiments showed that the best bacterium with high nitrate removal potential was Pseudomonas stutzeri, a member of the alpha subclass of the class Proteobacteria. The extent of nitrate removal efficiency was 99% at 200 mg/L NO[3] and the nitrite content of the effluent was in the prescribed limit. The experiments showed the ability of Pseudomonas stutzeri to rapidly remove nitrate under anoxic conditions. The strain showed to be potentially good candidate for biodenitrification of high nitrate solutions

[Comparison of ethanol, methanol and succinate effects as carbon sources on effluent biological denitrification]

Increase of nitrate concentration in water sources is becoming a serious problem in many parts of the world. Nitrogen containing compounds released into environment can create serious problems, such as eutrophication of water sources and hazard potential to human health, because it has potency of causing methemoglubinemia disease and cancer. Between recommended methods, biological denitrification is an effective method to remove nitrate from water and wastewater. In this study, biological nitrogen removal process was evaluated using ethanol, methanol and succinate as different organic carbon sources in batch scale. The different parameters, carbon source, initial nitrate concentration, pH, and inoculated of bacteria were evaluated. The experimental results were showed that bacteria can not use methanol as carbon source. The dinitrifyers bacteria can dissimilate 200 mg/L No3-N, in the optimum condition: 28 °C, pH 7.2 and initial inoculation of 3x 10[8] CFU/ml, respectively. In the process, produced nitrate-N was less than 1 mg/I. The bacterium Pseudomonas stuizeri can use ethanol as carbon source for biological denitrification, but efficiency of succinate was better than ethanol

Application of impregnated almond shell activated carbon by zinc and zinc sulfate for nitrate removal from water

In this study impregnated almond shell activated carbon by Zn° and ZnSO[4] were used as adsorbent with a particle size of 10-20 mesh. The objective of this research was to determine the ability of impregnated activated carbon in nitrate removal. The modified activated carbon had 1mm effective size, with a uniformity coefficient of 1.18. Potassium nitrate solution was used in batch adsorption experiments for nitrate removal from water. The effects of nitrate concentration, activated carbon dosage and time of contact were studied. Experimental data showed that modified activated carbon by Zn° and ZnSO[4] was more effective than virgin almond activated carbon for nitrate removal. The maximum nitrate removal was 64%-80% and 5%-42% for modified activated carbon and virgin activated carbon, respectively. While virgin activated carbon used, nitrate-N decreased from 20 to 15mg/L in 30min reaction. The final nitrate concentration was not in the standard range of WHO recommendations for water quality; while impregnated activated carbons were used, nitrate drcreased to <10mg/L. Maximum removal was over 16-17mg nitrate-N per 1g activated carbon for impregnated activated carbon. The experiments were conducted at pH=6.2, 20°C and initial concentrations of 20mg/L nitrate-N. Increase in modified activated carbon dosage increased the nitrate removal efficiency. The equilibrium time was found to be 45min for modified activated carbon

Photocatalytic decomposition of gaseous toluene by TIO[2] nanoparticles coated on activated carbon

Volatile organic compounds are considered as a group of major environmental pollutants and toluene is recognized as one of the representatives. In this research, the photocatalytic activity for toluene removal was studied over TiO2 nanoparticles embeded on activated carbon. Laboratory-scale experiments were conducted in a fixed-bed reactor equipped with 4 w and 8 w UV lamps [peak wavelength at 365 nm] to determine the oxidation rates of toluene. The photocatalyst was extensively characterized by means of X-ray diffraction and scan electronmicroscopy. Experiments were conducted under general laboratory temperature [25°C +/- 2] while the irradiation was provided by the UV lamps. The dependence of the reaction rate on light intensity as well as the deactivation of the catalyst were determined. The results indicated that the rate of the photocatalytic process increased with increasing the intensity of UV irradiation. Using the UV-A lamps, the decomposition rate of toluene was 98%. The stabilized photocatalyst presented remarkable stability [no deactivation and excellent repeatability]. The catalyst could be regenerated by UV irradiation in the absence of gas phase. The control experiments confirmed that the photocatalytic effects of toluene onto the TiO2/activated carbon catalysts in the dark conditions were negligible. Reproducibility tests proved that the photocatalytic activity of the photocatalyst remains intact even after several experiments of new added toluene quantities. The study demonstrated that the TiO2/activated carbon catalyst may be a practical and promising way to degrade the toluene under ultraviolet irradiation