Jurijs Ozolins

Disinfection effect of electrochemically generated chlorine on surface associated Escherichia coli in a drinking water system

AbstractFor many years, electrochemical treatment has been proposed as a potential alternative to conventional drinking water chlorination due to its simplicity, ease of use and ability to generate active disinfectant from ions naturally found in the drinking water The aim of this study was to evaluate the survival of Escherichia coli on the surfaces of water distribution system after exposure to in situ electrochemically generated chlorine. To analyse the effect of chlorine and its reaction intermediates, completely mixed reactor with or without ingenuous biofilm was supplied with natural drinking water containing low amount of chloride ions (<10 mg/L) and treated with non-stoichiometric titanium oxide electrodes (TiO2−x) at low current density (4.1–8 mA/cm2) which generate predominantly chlorine species. Various cell viability markers (cultivability, ability to divide as such and respiratory activity) were assessed in this study. The results showed that electrochemical disinfection was very effective to...

Studies of TiO2 Ceramics Structure after Thermal Treatment at Different Conditions

The present work describes results of investigation of structural characteristics of TiO2 ceramics, depending on temperature and thermal treatment conditions by using a variety of characterization techniques. TiO2 ceramics was prepared by extrusion method and developed as a material for electrodes for innovative water treatment technologies. It was shown that non-stoichiometric phase TiO1.95 was observed after thermal treatment of TiO2 ceramics under high vacuum conditions.

Effects of Surface Modification of Titania on In Vitro Apatite-Forming Ability

Surface properties of a material play a significant role in manipulating biological response of living body to artificial materials. The aim of this work was put on bioactivity assessment of TiO2 ceramic after thermal treatment and further surface activation with UV-light. The in vitro apatite-forming ability was examined by soaking the samples into the simulated body fluid for several days. The research shows that nanostructural surface and UV irradiation accelerates formation of apatite on TiO2 pellets.

Properties of recycled polypropylene based composites incorporating treated hardwood sawdust

The effect of different treatment of hardwood sawdust under mild conditions on contact angles, adhesion energy and water sorption was studied. A comparison of these indices for the hardwood treated sawdust and the composites filled with them was performed. The treatment promoted the compatibility between the recycled polypropylene and the hardwood filler. The inclusion of the lignin-based compatibiliser in the composite, containing the ammoxidised wood filler, essentially improved its mechanical properties.

Illite Clay Ceramic Hollow Sphere - Obtaining and Properties

This work focuses on clay ceramic hollow spheres (CCHS) preparation using Liepa clay and sacrificial template method in a lab scale device and testing of their properties. Water retention and compression strength were investigated in order to found out if obtained CCHS can be used as an additive for improving soil resilience.The synthesis and characterization of CCHS using expanded polystyrene spheres (EPS) as sacrificial template is presented. CCHS were fired at five different temperatures and their compressive strength, water retention, bulk density, material density, water absorption, phase composition, surface morphology, porosity using hydrostaticweighing and BET nitrogen adsorption methods, were determined.Study of clay ceramic hollow sphere structure and surface morphology revealed that all samples have spherical shape. These spheres have several pronounced protrusions from the granulation process. Clay ceramic hollow spheres have porosity rate of 21 - 36% and a water absorption rate of 15 -33%. The highest rate of porosity and water absorption was observed for hollow spheres fired at 1050°C.The increase of clayceramic hollow spheresfiringtemperature led to decrease of specific surface area-thehighestvaluewas observed at950°C and the lowest at 1150°C. The bulk density increased at 1150°C.Mechanicalstrength test of ceramic hollowspheres(HS)revealedthat with the increase of scorchingtemperature the compression strength of the spheres increasedas well.The sphere hollowshadpractically globular shape with the averagewallthickness of0,6 mm, whichcomprises10-13% ofthe outer diameter.The obtained clay ceramic hollow spheres are proposed as water retention agent.

Drinking Water Disinfection with Electrolysis

Nowadays electrochemical disinfection has gained an increasing attention as an alternative to conventional drinking water disinfection, since it is regarded as environmentally friendly, amendable to automation, inexpensive, easily operated and is known to inactivate a wide variety of microorganisms from bacteria to viruses and algae. We found that along with increasing the number of electrodes in our equipment from 2 to 24, the resistance of chlorine-generating electrolytic cell and specific work of electric current decreased. During the electrolysis the amount of generated Cl2 increased along with the increase of chloride ion concentration in the solution and the intensity of electric current. The technological process parameters (flow rate, current intensity) have been established to obtain a predetermined amount of generated chlorine during the electrolysis process. A comparison of flow and circulating (3 times) regimes for electrolysis of tap water with chloride ion concentration below 10 mg/L showed that circulation is necessary to generate active chlorine (above 1 mg/L). At the same time, when no circulation was performed, even a 0.9 A treatment was not enough to generate detectable levels of free chlorine. Electrochemical disinfection of tap water with non-stoichiometric titanium oxide electrodes was effective enough to inactivate both metabolically active and cultivable bacteria E. coli to undetectable levels within 15 minutes at 0.5 A current intensity. Mūsdienās ūdens elektroķīmiskajai dezinfekcijai, kā alternatīvai tradicionālajām dezinfekcijas metodēm, tiek pievērsta liela uzmanība, jo tā ir videi draudzīga, viegli automatizējama, salīdzinoši lēta, viegli vadāma un ir zināma tās dezinficējošā iedarbība uz plašu mikroorganismu klāstu - no baktērijām līdz vīrusiem un aļģēm. Eksperimentāli konstatēts, ka, palielinot elektrodu skaitu elektrolīzes iekārtā no 2 līdz 24, tās pretestība un strāvas īpatnējais darbs samazinājās. Izdalītā Cl2 daudzums elektrolīzes laikā palielinājās, palielinoties hlorīda jonu koncentrācijai šķīdumā un elektriskās strāvas stiprumam. Variējot elektrolīzes procesa tehnoloģiskos parametrus (ūdens plūsmas ātrumu, strāvas stiprumu), iespējams sasniegt noteiktu izdalītā hlora daudzumu. Salīdzinot ūdens, kurš satur hlorīda jonus mazāk par 10 mg/L, apstrādi ar elektrolīzi caurplūdes režīmā ar cirkulācijas režīmu (3 reizes), konstatēts, ka ūdens apstrādi vēlams veikt cirkulācijas režīmā, lai būtu iespējams saražot vairāk aktīvā hlora (koncentrācijā, lielākā par 1 mg/L). Noteikts, ka process, veicot ūdens apstrādi ar elektrolīzi caurplūdes režīmā pat, ja strāvas stiprums 0,9 A, nenodrošināja aktīvā hlora veidošanos detektējamos daudzumos. Elektroķīmiskā dezinfekcija, izmantojot nestehiometriskā titāna oksīda elektrodus, bija pietiekami efektīva, lai pilnībā inaktivētu metaboliski aktīvās un kultivējamās E. coli baktērijas 15 minūšu laikā, ja strāvas stiprums 0,5 A.

Investigation of TiO2 Ceramic Surface Conductivity Using Conductive Atomic Force Microscopy

Dense TiO2 (rutile) ceramic samples were prepared by sintering compacts of titanium dioxide anatase powder at 1500 °C for 5h. Sintered samples were polished and annealed in vacuum at 1000 °C for 1h. Structural properties of the samples were studied by X-ray diffraction, polarized light and scanning electron microscopy. The surface topography and local electrical conductivity of the samples were investigated by atomic force microscopy technique under atmospheric conditions. Enhanced electrical conductivity was observed at grain boundaries while the polished, vacuum annealed grains surface showed non-homogeneous conductivity.

Hydrophilic-Hydrophobic Characteristics of Wood-Polymer Composites Filled with Modified Wood Particles

In this study, hydrophobic-hydrophilic characteristics, including contact angle and moisture sorption of a modified wood filler and the wood-polymer composites (WPC) containing it was investigated. The wood filler obtained from aspen sawdust was modified by mild acid hydrolysis and by ammoxidation. Contact angles of the wood particles and the WPC samples were measured with Kruss K100M using the Washburn and Wilhelmy methods, respectively. Work of adhesion was calculated using Young-Dupre equation. Surface free energy as well as its dispersive and polar parts were found using Owens-Wendt-Rabel-Kaelble approach. It was found that the hydrolysis and the ammoxidation led to decrease of the hemicelluloses content in the lignocellulosic matrix. Beside this, the ammoxidation favours the formation of amide bonds in the ammoxidised particles. These changes enhanced the contact angles, decreased the work of adhesion, and decreased surface free energy of the WPC samples filled with the modified particles in comparison with the WPC sample that contained the unmodified ones. The treatment of the wood particles decreased the wettability towards water, but increased it towards recycled polypropylene. This positively effects mechanical properties of the samples.

Surface Energetic Characteristics of Wood-Polymer Composites, Containing a Valorised Hardwood By-Product

The aim of the study was to evaluate the surface energetic characteristics of wood-polymer composites (WPCs) based on recycled polypropylene (rPP) filled with ammoxidised lignocellulosic microparticles, obtained from aspen sawdust, a by-product of a Latvian company. The aspen sawdust, pre-hydrolysed in acidic medium, was treated with a reaction mixture of ammonium persulphate and NH4OH solution at their defined mass ratio during 120 h. The content of the introduced nitrogen was varied from 1,05 to 2,10%. It was found that the ammoxidation that was accompanied with the formation of amide linkages and the decrease of the hemicelluloses content enhanced the contact angles, decreased the work of adhesion and reduced the surface free energy of the WPC samples in comparison with the case of the composite filled with the initial sawdust. The valorisation of the wood particles increased their wettability towards the recycled polypropylene that had a positive effect on the WPC samples’ mechanical properties.

Electrophoretic Deposition of TiO2 Nanoparticles on Dense TiO2-x Ceramic Electrodes

TiO2 nanoparticles were electrophoretically deposited on the dense TiO2-x ceramic electrodes from suspension containing TiO2 nanoparticles, isopropanol as a solvent and triethanolamine as dispersant. The effect of deposition parameters including deposition voltage (10 to 60 V) and deposition time (10 to 40 min) on the microstructure and deposition yield was examined. It was found that the thickness of coating increased with increasing deposition time and deposition voltage. However, it affected the quality of obtained coating e.g. cracks and holes were observed. Optimizing deposition parameters homogeneous coating with smooth microstructure and limited surface damage can be obtained. Thermal treatment of the coating in the temperature range from 700 to 1100 °C causes anatase to rutile phase transformation. Crack formation was noted during sintering due to the phase transformation and thermal stresses.