Mathematical modelling of wet oxidation of excess sludge
A mathematical model enabling a quantitative description of wet oxidation of excess sludge in continuous bubble columns is proposed. The model consists of mass and heat transfer kinetic equations and material and heat balance equations of gas and liquid phases flowing through the absorber. The equations of material and heat balance refer to a parallel, co- current flow of gas and liquid phase and take into account a complex chemical reaction in the liquid phase core. The proposed model was used in a numerical simulation of wet oxidation in a bubble absorber for different process conditions: flow rate and composition of the gas and liquid phase, temperature and pressure, and different heights and diameters of the column.
Klara Piotrowska, Mirosław Imbierowicz and Andrzej Chacuk
Wet Oxidation of Dairy Sewage
Results of kinetic studies on the process of wet oxidation of dairy sewage are presented. Experiments were carried out in a stirred batch tank reactor at the oxygen partial pressure equal to 1 MPa and at temperature ranging from 473 to 523 K. Dairy sewage was subjected to oxidation at a natural pH close to 4. The efficiency of decomposition of organic compounds was estimated on the basis of TOC measurement. The highest TOC reduction rate reached 79.6%. A kinetic model of the process was proposed and its parameters were determined experimentally. Good agreement of the experimental and calculated results was obtained.
Mateusz Wymysłowski, Małgorzata Łuczak, Alicja Zawadzka, Mirosław Imbierowicz and Andrzej Chacuk
Methane fermentation of poultry slaughterhouse waste
One of the alternative methods for the treatment of animal by-products is their utilization in biological processes with a simultaneous production of energy-rich biogas. The results of the investigations of methane fermentation of animal waste are discussed in the study. The methane fermentation was carried out at 35°C. The substrates used in the experiments included poultry heads and muscle tissue. Furthermore, the fermentation residues subjected previously to hydrothermal processing were used as a substrate. The suspension of those substrates in the initial concentration range from 1 g TOC/dm3 to 11 g TOC/dm3 was used in the process. Additionally, the effect of the preliminary stage of hydrothermal substrate processing on methane fermentation efficiency was assessed. Poultry waste was subjected to thermohydrolysis at the temperature from 100°C to 300°C and pressure up to 9.0 MPa. The efficiency of the methane fermentation was estimated on the basis of biogas generated in the process. The biogas production was between 0.17 Ndm3/g TOC and 1.53 Ndm3/g TOC. In the case of poultry heads, a beneficial impact of hydrothermal processing at the temperatures from 100°C to 175°C was confirmed. For poultry meat the preliminary thermohydrolysis brought about a decrease of methane fraction in the biogas evolved. The preliminary hydrothermal processing made it possible to meet the requirements of legal regulations for the hygienization of by-products of animal origin. The obtained results allowed us to identify conditions under which the methane fermentation was carried out and which ensured a high level of methanization.
Klara Piotrowska, Mirosław Imbierowicz and Andrzej Chacuk
The article presents the results of kinetic studies of the wet oxidation process of dairy sewage. The dairy sewage, obtained straight from the production line, was subjected to oxidation at pH close to the natural value of 7. Experiments were carried out in a stirred batch tank reactor at the oxygen partial pressure equal to 1 MPa and at temperature ranging from 473 to 593 K. The effectiveness of organic compounds decomposition was estimated based on the measurement of TOC. The kinetics of decomposition of milk components, ie lactose, protein and fat, as well as the kinetics of oxidation of intermediate products was the aim of the study. Measurement of the concentration of protein, fat and lactose was done with a milk composition analyzer, calibrated in relation to the dairy sewage. The obtained results were used to develop a mathematical model of wet oxidation of dairy sewage, including the group of analyzed compounds.
Aleksandra Ziemińska-Stolarska, Janusz Adamiec, Mirosław Imbierowicz, Ewa Imbierowicz, Marcin Jaskulski, Aleksander Szmidt and Ireneusz Zbiciński
The paper presents methodology of accurate mobile measurements of water quality parameters such as temperature, dissolved oxygen, chlorophyll “a” concentration, ammonium ion concentration, conductivity, pH and blue-green algae content in water. The measurements (probe EXO 2, YSI, USA) were made on various depths of probe immersion (1.5, 2.5 and 3.5 m) and at different towing speeds of the probe (approx. 5.4 and 9.0 km/h). Static measurements carried out on the same route provided reference values for the measurements in motion to compare the repeatability of static and mobile methods. The tests were also evaluated by observation of probe behavior in motion, e.g. water disturbance intensity, access of light (sun rays) to the sensors. Statistical tests confirmed that the mean values of water quality parameters from mobile measurements with the speed of 5.4 km/h at the depth 1.5 m does not differ from the stationary measurements. Results of statistical analysis prove that water quality parameters can be measured accurately keeping established speed of towing the probe at the fixed depth. Methodology of mobile measurements elaborated in the frame of this work allows to collect vast number of data which can be used to obtain GIS point maps of water quality parameters in large water bodies.