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1

Rheopectic behavior of rendered fat

100%

Travnicek P. , Krcalova E. , Vitez T.

Polish Journal of Environmental Studies

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2013

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tom 22

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nr 5

EN

Waste fat is an integral part of the processing of animal by-products in rendering plants. The flow behavior and time-dependent flow properties of waste fat in the temperature range of 10ºC, 20ºC, 30ºC, and 62ºC was studied. Waste fat presented non-Newtonian behavior. Three mathematical models were used for prediction of the flow behavior of waste fat, including the Casson, Steiger-Ory, and Herschel-Bulkley models. The Herschel-Bulkley model sufficiently described the flow behavior of the waste fat at different temperatures. Several kinds of rheological curves were determinated for description of the flow behavior. Rheopectic behavior of rendered fat was determinated at temperatures lower than 30ºC.

2

Microbial contamination of screenings from wastewater treatment plants

100%

Szostkova M. , Vitez T. , Marecek J. , Losak T.

Polish Journal of Environmental Studies

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2012

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tom 21

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nr 6

EN

Screenings represent the type of waste resulting from the primary treatment of wastewater. Their content varies significantly and it depends on numerous factors. The microbial contamination of screenings has not yet been monitored in detail; therefore, information in this area is either insufficient or unavailable. Our objective was to analyze the indicative microorganisms present in the screenings from wastewater treatment plants. Faecal thermo-tolerant coliform bacteria, coliform bacteria, and enterococci were monitored during microbial analyses. All tested samples proved the presence of the aforementioned microorganisms (in different concentrations). Furthermore, some samples confirmed the presence of Salmonella sp. bacteria, which originate from the faecal solids getting to the trash screens of the wastewater treatment plants together with contaminated water.

3

Rheological measurements of disintegrated activated sludge

75%

Travnicek P. , Vitez T. , Junga P. , Krcalova E. , Sevcikova J. , Marecek J. , Machal P.

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nr 4

EN

Our paper deals with the description of the rheological properties of activated sewage sludge before and after disintegration. There is an assumption that disintegrated activated sewage sludge is able to change rheological properties. These changes probably cause the modification of the structure of activated sewage sludge after disintegration. The reason is that during disintegration, cell walls of organisms (from which the activated sewage sludge is composed) are disturbed. Currently there are not published many papers that deal with rheological properties of disintegrated activated sewage sludge. There is therefore no opportunity to confront our assumption with papers of other authors. The sample of activated sewage sludge was collected from aeration tank of the wastewater treatment plant for 10,000 population equivalent (PE). In our work the following rheological properties were described: temperature dependence on viscosity and the shear stress dependence on shear rate. On the basis of measured data Arrhenius mathematical model has been applied. By using this mathematical model the activation energy has been obtained.

4

Study of rheological behaviour of wines

75%

Travnicek P. , Burg P. , Krakowiak-Bal A. , Junga P. , Vitez T. , Ziemianczyk U.

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nr 4

EN

This study deals with rheological properties of various wine varieties. Samples of the following wines were used for this experiment: André, Cabernet Moravia, Laurot, Saint Laurent, Gruner Veltliner, Pinot Blanc, Müller Thurgau, and Riesling Italico. These samples were obtained from wine produced from the grapes collected in the Czech Republic (Morava region, subregion Velke Pavlovice). In the first phase, the chemical composition of the samples was determined. The following chemical parameters were determined: total acidity, pH, content of the alcohol, reduced sugars, free SO2, total SO2, and volatile acids. In the second phase of the study, the physical properties of the samples were determined and the samples of the wines were subjected to rheological tests. These tests consisted in determination of apparent viscosity in relation to temperature, hysteresis loop tests, and apparent viscosity related to time. The dependence of the shear rate on the shear stress was described with the Herschel-Bulkley mathematical model. The experiment yielded the following findings: seven out of the eight samples behaved as non-Newtonian fluids at low temperature (5°C); non-Newtonian behaviour was changed into Newtonian at the temperature higher than 10 °C; non-Newtonian behaviour was characterised as thixotropic behaviour; the degree of thixotropy is relatively small and reaches 1.85 Pa s-1 ml-1.

5

Comparison of the effectiveness of applications of mineral fertilisers and digestate from a biogas station on yields, content of dry matter and micronutrients in the aboveground biomass of maize (Zea mays L.)

51%

Losak T. , Goncalves T. V. F. , Musilova L. , Zatloukalova A. , Fryc J. , Vitez T. , Vitezova M. , Skarpa P. , Hlusek J. , Marecek J. , Wisniowska-Kielian B. , Kovacik P.

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tom 106