Suchergebnisse

AbstractOzonation is a powerful technique to remove micropollutants from wastewater. As chemical oxidation of wastewater comes with the formation of varying, possibly persistent and toxic by-products, post-treatment of the ozonated effluent is routinely suggested. This study explored an enzymatic treatment of ozonation products using the laccase from Trametes versicolor. A high-performance liquid chromatography coupled with high-resolution mass spectrometry (HPLC-HRMS) analysis revealed that the major by-products were effectively degraded by the enzymatic post-treatment. The enzymatic removal of the by-products reduced the ecotoxicity of the ozonation effluent, as monitored by the inhibition of Aliivibrio fischeri. The ecotoxicity was more effectively reduced by enzymatic post-oxidation at pH 7 than at the activity maximum of the laccase at pH 5. A mechanistic HPLC-HRMS and UV/Vis spectroscopic analysis revealed that acidic conditions favored rapid conversion of the phenolic by-products to dead-end products in the absence of nucleophiles. In contrast, the polymerization to harmless insoluble polymers was favored at neutral conditions. Hence, coupling ozonation with laccase-catalyzed post-oxidation at neutral conditions, which are present in wastewater effluents, is suggested as a new resource-efficient method to remove persistent micropollutants while excluding the emission of potentially harmful by-products.
Graphical abstract

AbstractThe aim of this study was to evaluate the potential use of ozonation with pharmaceutical compounds on membrane bioreactor (MBR). The result has shown that high concentrations of pharmaceutical contaminants have caused destruction of cell wall, thereby reducing mixed liquor suspended solids (MLSS). It also resulted in high amounts of biopolymers in the presence of non‐biodegradable pharmaceutical compound in MBR. As a result, biological removal decreased and membrane fouling happened. Ozonation treatment reached a chemical Oxygen Demand (COD) removal of 99.9% and caused better effluent quality. The MBR‐ozonation process could achieve an acetaminophen and fluoxetine removal of around 98.4 and 57.83%, respectively.

The aim of this research was evaluate the efficiency of the action of ozonation of milk on the reduction of the bacterial counts of Staphylococcus aureus artificially inoculated and subjected to different binomials times/concentrations of ozone. The samples were divided in four assays: 1 and 2, with skim milk and ozone concentrations of 34.7 mg L –1 and 44.8 mg L-1, respectively, and assays 3 and 4, with whole milk and the same concentrations of ozone. The time of ozonation in all of the assays was 5 (T1), 10 (T2), 15 (T3), 20 (T4) and 25 (T5) minutes. Each treatment was replicated three times. The bacterial counts were determined immediately before and after the ozonation process by plating the samples on Baird Parker agar. In treatments 1 and 2, the greatest reductions were 0.42 log10 CFU/mL (colony forming units per millilitre), whereas in treatments 3 and 4, the greatest reductions were 0.19 and 0.21 log10 CFU/mL, respectively. The results of all of the tests show that, for T1, there was no reduction in the microbial load, whereas for T2, there was a sharp decrease in the microbiota, and this decrease was even more significant for T4 and T5. In both skim and whole milk with ozone concentrations of 34.7 and 44.8 mg L-1, the reductions were significantly greater after 20 minutes of ozonation. The results indicated that ozone showed low efficacy in the reduction of S.aureus inoculated into fluid milk and milk fat interferes with the bactericidal action of the gas.