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Analysis of precipitation regime in Šumava Mountains
Šípek, Václav ; Zelíková, Nikol
The analysis is focused on the description of precipitation regime in the Šumava National Park in comparison with other mountain ranges in the Czech Republic. The period of interest comprised the years 2001-2019. The daily and monthly precipitation amounts were compared to the reference period covering the years of 1971-2000.
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Correlation between the onset of beadless character of nanofibrous webs and rheological characteristics of electrospun polymer solutions
Zelenková, Jana ; Peer, Petra ; Filip, Petr
An overwhelming majority of applications of nanofibrous webs requires sufficiently smooth character of nanofibres surface. This character is apart other parameters strongly influenced by a concentration of chosen polymeric material in the solvents. Qualitative attributes roughly depend on the prepared concentration, specifically whether it belongs to one of the four basic regions: dilute, semidilute unentangled, semidilute entangled and concentrated. A concentration separating the latter two regions is often taken as a zero-th approximation indicating an onset of beadless nanofibrous webs. The present contribution uses as a more precise indicator behaviour of so-called phase angle relating viscous and elastic moduli, in other words mutual participation of viscous and elastic components. To this aim three frequently used polymers were used: copolymer of poly(vinylidene fluoride) and hexafluoropropylene (PVDF-co-HFP), poly(ethylene oxide) (PEO) and poly(vinyl butyral) (PVB). For materials exhibiting first a constant behaviour or moderate decrease in a phase angle for lower concentrations, an approximation of the starting concentration is given by a concentration value where a phase angle curve starts to decrease, apparently reflecting a more progressive viscoelastic nature. As shown, such approximation provides relatively very good approximation enabling to eliminate a traditional trial-and-error method.
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Chemical-technological audit of the WTP Tlumačov - assessment of the technology of suspension formation and separation
Pivokonský, Martin ; Čermáková, Lenka ; Prokopová, Michaela ; Fialová, Kateřina ; Sochorová, H. ; Haidl, Jan
The report describes the assessment of the sludge formation and separation technology at the WTP Tlumačov in two measuring cycles (summer 2020 and spring 2021) in profiles: i) aeration, ii) effluent from the reaction tank, iii) flocculation, iv) sediment inflow, v) after sedimentation, vi) inflow to filtration, vii) after filtration, on the right and left line of ÚV Tlumačov. The report assessed the quality of raw and treated water and the effectiveness of destabilization and aggregation. The preparation of the suspension in the phase of fast and slow mixing and separation of flakes were evaluated. Aggregation tests (sedimentometric analysis) were used for this purpose.
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Antibacterial electrospun membrane prepared from poly(vinylidene fluoride)-co-hexafluoropropylene with lauric acid monoacylglycerol
Zelenková, Jana ; Peer, Petra ; Pleva, P. ; Janalíková, M. ; Sedlaříková, J. ; Filip, Petr
The aim of this study was to prepare an antibacterial nanofibrous membrane using electrospinning technique. The nanofibrous membranes were spun from polymer solution of poly(vinylidne fluoride)-co-hexafluoropropylene (PVDF-co-HFP) dissolved in N,N´-dimethylformamide. Monoacylglycerol of lauric acid (MAG C12) was used as an antimicrobial agent at the concentrations ranging from 1 to 3 wt%. The impact of MAG C12 incorporation on the rheological, structural and antibacterial properties was investigated. The rheological tests of polymer solutions, as steady shear and oscillatory shear, proved that addition of MAG C12 changed marginally rheological quantities such as viscosity, elastic (storage) and viscous (loss) moduli. Measurement of mean nanofibres diameter indicated a slight decrease with increasing MAG C12 concentration. Antimicrobial activity of PVDF-co-HFP nanofibre membranes with incorporated MAG C12 against Gram-positive bacteria Staphylococcus aureus and Gram-negative Escherichia coli was studied. An antibacterial activity was revealed for the samples containing MAG C12 at all concentrations against Gram-positive bacteria Staphylococcus aureus by the disk diffusion method.
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Magnetic properties of electrospun polyvinyl butyral/Fe2O3 nanofibrous membranes
Peer, Petra ; Cvek, M. ; Urbánek, M. ; Sedlačík, M.
In this contribution, magnetic Fe2O3 nanoparticles (MNPs) were successfully incorporated into the polyvinyl butyral (PVB) nanofibrous membranes using the electrospinning process. The effects of the MNP concentration on the morphology of the nanofibres and their magnetic properties were investigated. Scanning electron microscopy and transmission electron microscopy confirmed their concentration-dependent, yet uniform diameter, and the presence of well-embedded MNPs inside the PVB nanofibres. The magnetic properties of the PVB/MNP membranes were studied using the vibrating-sample magnetometry. The saturation magnetization increased from 6.4 to 45.5 emu/g as the MNP concentration in the feedstock solution increased from 1 to 15 wt%. The fabricated PVB/MNP nanofibrous membranes possessed the ability to respond to the external magnetic fields, which determines their potential in the development of the advanced smart textiles.
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Optimization of the coagulation process at the Březová water treatment plant
Pivokonský, Martin ; Čermáková, Lenka ; Prokopová, Michaela ; Pivokonská, Lenka
The presented report deals with the description of raw water quality focusing mainly on the nature of the contained organic substances, then a comprehensive evaluation of the operational efficiency of existing aggregation and laboratory optimization of coagulation operating parameters - especially the dose of coagulant and reaction pH. Coagulation in combination with sedimentation and sand filtration must be understood not only as the first stage of water treatment before ultrafiltration, but also as protection of the membranes themselves from their clogging, especially by macromolecular organic substances. From this point of view, it is necessary to operate coagulation with subsequent separation of aggregates with the maximum possible efficiency.
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