Dual-wavelength UV degradation of bisphenol A and bezafibrate in aqueous solution using excilamps (222, 282 nm) and LED (365 nm): yes or no synergy?

Dual-wavelength ultraviolet (DWUV) irradiation can lead to a synergistic effect in terms of accelerated degradation of emerging organic contaminants in aqueous media. This study compared the kinetics of single-wavelength and DWUV degradation of bisphenol A (BPA) and bezafibrate (BZF) in model aqueous solution using KrCl (222 nm), XeBr (282 nm) excilamps and LED (365 nm). Three novel dual combinations (222 + 282, 222 + 365 and 282 + 365 nm) were examined toward the potential synergy in direct photolysis and advanced oxidation processes (AOPs) using potassium persulfate and hydrogen peroxide. Kinetic comparison showed that the time- and fluence-based synergy did not occur in the dual combinations selected. Meanwhile, the single-wavelength UV treatment using KrCl excilamp was found to be highly efficient for degradation of target contaminants. At a given dosage of oxidants, the UV/S2O82- process exhibited higher performance than the UV/H2O2 one, attaining higher degradation rates and requiring lower UV fluences for 90% removal. This study demonstrates that the catalyst-free UV/S2O82- process using KrCl excilamp has a high potential for efficient removal of such organic contaminants from real waters with low turbidity.

UV treatment of microorganisms on artificially-contaminated surfaces using excimer and microwave UV lamps.

An XeBr excilamp having a peak emission at 283 nm, and microwave UV lamps with peak emissions at 253.7 nm that also generate ozone, have been tested for ability to eradicate high populations of microbial vegetative cells and spores (of bacteria and fungi) artificially added to filter surfaces. The study examined the energy required to completely eradicate large populations on filter surfaces. It was found that both the excilamp and microwave UV lamps were effective at killing large populations on surfaces with killing efficiency dependant on the type of organism, and, whether present in its vegetative or spore forms. The main killing factor is UV radiation following short treatment times. It is considered that for longer irradiation periods that are required to facilitate complete destruction of surface microorganisms, ozone and other oxidising species produced by microwave UV lamps would act to enhance microbial destruction.

Efficiency of KrCl excilamp (222 nm) for inactivation of bacteria in suspension.

AIMS: To examine the killing efficiency of UV KrCl excilamp against gram-positive and gram-negative bacteria. METHODS AND RESULTS: Vegetative cells of Bacillus cereus, Bacillus subtilis, Escherichia coli O157:H7, Staphylococcus aureus and Streptococcus pyogenes at initial populations from 10(2) to 10(7) colony-forming units (CFU) ml(-1) were treated by KrCl excilamp in sterile Ringer's solution with and without H(2)O(2). The number of viable cells was determined using spread plating techniques and nutrient agar method with subsequent incubation at 28 degrees C or 37 degrees C for 24 h. At estimated populations of 10(2)-10(5) CFU ml(-1) E. coli O157:H7 and Staph. aureus were the most sensitive and showed 100% disinfection within 15 s (29.2 mJ cm(-2)). Bacillus subtilis was more sensitive to UV treatment than B. cereus. The UV/H(2)O(2) inactivation rate coefficients within this population range were two times higher than those observed for UV treatment alone. No effect of H(2)O(2) was observed at 10(7) CFU ml(-1) for Bacillus sp. and Strep. pyogenes. CONCLUSIONS: The narrow-band UV radiation at 222 nm was effective in the rapid disinfection of bacteria in aqueous suspensions. SIGNIFICANCE AND IMPACT OF THE STUDY: KrCl excilamps represent UV sources which can be applied for disinfection of drinking water in advanced oxidation processes.

[Bacillus cereus is a microbial decomposer of 2,4-dichlorophenol].

A microorganism degrading 2,4-dichlorophenol isolated from an aeration pond of the Baikal Pulp and Paper Mill was identified as Bacillus cereus BIP507 based on morphological and physiological characters as well as 16s rDNA sequencing. This microorganism proved able to degrade high 2,4-dichlorophenol concentrations (up to 560 microM).

[Effect of pH on the permeability and mechanical properties of intercellular contacts in the small intestinal epithelium]. / Vliianie pH na pronitsaemost' i mekhanicheskie svoistva mezhkletochnykh kontaktov épiteliia tonkoi kishki.

It is shown that acid site population controlling ion permeation through cell contacts is localized in the region of tight junction. The isoelectric point of cell surface in the region to tight junction changed from mean pH = 2.37 +/- 0.1 for duodenum to pH =2.80 +/- +/- 0.1 for ileum. The maximum of cell adhesion in the tissue reached at mean pH that corresponding the isoelectric point. It seems possible, that this acid site population take part in interaction of plasma membranes of neighbouring cells.