https://etalpykla.vilniustech.lt/handle/123456789/101017 2026-04-17T09:41:10Z https://etalpykla.vilniustech.lt/handle/123456789/160287 Mathematical modelling of biofilter effectiveness in pH regimes Vaiškūnaitė, Rasa The efficiency of a biofilter filled with pine bark charge was modelled under conditions of interchanging pH. Hydrogen ion concentration is significance for the growth of microorganisms, therefore biological metabolism is strongly dependent on pH. Many microorganisms will only grow within a particular pH range. Since pH has a strong influence on kinetic parameters and governs the process into the biofilm, proton concentration (H+) was included as a state variable in the model. Different approaches to model pH variations in biological systems can be found in literature. The biofilter model was implemented in a home-made simulation environment developed in MATLAB. Model evaluation was performed by comparison of model predictions with experimental data obtained in the pine bark charge of biofilter. The model was able to predict qualitatively and quantitatively the behaviour of the system under dynamic conditions, particularly for pH. Modelling were performed with different pH regimes (4, 5, 6, 7, 8, 9 and 10) in the charge filled with pine bark. Moreover, the dependence of the filter efficiency on its charge height (0.15–0.75 m) with different initial pollutants (xylene, butanol and buyl acetate) concentrations and at different velocity of passing air (0.02–0.1 m/s) were modelled. Similar to experimental tests, the increase in the charge height from 0.15 to 0.75 m results in the increase in cleaning efficiency. For example, when the pH of 7 is maintained in the biocharge and the air is being cleaned of butyal acetate (with its initial concentration of 74 mg/m³) the efficiency of removal of butyl acetate starting with the height of the charge equal to 30 m is 70.1 %, starting with the height of 60 m is 77.6 %. Furthermore, modelled expression were similar to experimental data of the air flow rate results in the decreased efficiency of the biofilter. Respectively, when the pH of 7 is maintained in the charge and the air is beeing cleaned of xylene (with its initial concentration of 63 mg/m³), with the velocity of the passing air increased from 0.04 to 0.08 m/s, air cleaning efficiency significantly reduces from 76.8 to 68.3 mg/m³. Therefore, mathematical expression of environmental processes such us biofiltration lighten theoretical calculations and seek ultimate air cleaning efficiency. 2011-01-01T00:00:00Z https://etalpykla.vilniustech.lt/handle/123456789/160286 Mathematical simulation of aeration and diffusion processes in the air-water interface Vaidelienė, Adelė; Vaidelys, Vytautas This paper deals with problem of water aeration. Water aeration is important factor that influences process of open water self-purification. Aeration first of all depends on purely physical diffusion process taking place in the interface between air and water. Specific of the character of these processes was discussed. Also attention was paid to the features and behavior of air and water bubbles created in the falling water turbulence flow. The final goal of this paper was to describe these processes mathematically. Mathematical simulation kinetic equations describing air and water bubbles adsorption and desorption processes where proposed. The results show good coincidence with experimental data obtained by independent researchers. 2011-01-01T00:00:00Z https://etalpykla.vilniustech.lt/handle/123456789/160285 New and increasing occupational and industrial hazards Urnikytė, Laura; Sakenaitė, Jurgita In the recent decade a number of new and increasing hazards arose in the industry world-wide. Some of them can be attributed to the occupational field and some must be considered as hazards capable to initiate serious industrial accidents. In this paper, a review of occupational and industrial hazards is provided. The attention is focused on biological, chemical, physical hazards as well as psychosocial issues. Equipment aging, creation of networks and nanotechnologies are considered to be new and increasing industrial hazards. A separate consideration is devoted to the presence new and increasing hazards in Lithuanian industry. It is found that these hazards exist but are not very topical because Lithuania does not run highly dangerous technologies, plants and industrial branches which are hazardous to environment. A number of new and increasing hazards specific to Lithuanian industry are identified and analyzed. The consideration can provide recommendations for the companies which may face new and increasing hazards. 2011-01-01T00:00:00Z https://etalpykla.vilniustech.lt/handle/123456789/160284 Psychosocial work environment research on the situation in Lithuanian companies Urnikytė, Laura; Kaminskas, Kazys Algirdas Work Environment Assessment of psychosocial factors in practice quite a complex operation that requires specialized knowledge and expertise. The difficulty arises because many of the concepts of psychosocial factors and uncertainties of these factors depend on the employee’s subjective perception of the environment. Identification of these factors is necessary in order to keep workers mental health and to increase organizations economic efficiency. For psychosocial risk factors assessment are using a variety of questionnaires, for example, evaluation of stress at work questionnaire, the Copenhagen questionnaire, burnout syndrome questionnaire, the questionnaire of motivation at work, and others. Their individual goals are slightly different, but at the same time is the same – to set the stress level in the work environment. Although such research is carried out in the world long enough, Lithuania, this practice is taking its first steps. This work deals with the investigation, which took place in the presence of 25 Lithuanian companies 331 respondents. Subjects were presented four questionnaires, which revealed the existence of workplace psychosocial risk factors. It appears that the most stressful factor is the employee’s age and experience. This study revelled, that woman more than men suffer stress at work, as workers without higher education are more exposed to stress. It was also noted that the examination of the different questionnaires revealed the same problems that have the greatest impact on workers’ mental well-being - the pace of work, or a rush job, and employee opinion significance or influence at work. Observed and reported the problem, namely the emotional stress resulting from fatigue. The burnout syndrome menace 32.5 % of employees, 3.2 % – already have burnout syndrome. Just the quarter of respondents do not need worry about burnout syndrome, 35.1 % – should pay attention to mental health. It also shows the reasons respondent’s most stimulating work with. It was found that most surveyed firms in Lithuania to motivate employees to their work carried out by the content, only then - the financial motivation and success at work. The career perspectives are the weakest motivator in the surveyed companies. 2011-01-01T00:00:00Z