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    Physico-Mechanical Properties and Hydration Processes of Cement Pastes Modified with Pumice, Trass and Waste Chalcedonite Powder
    (MDPI, 2023-12-31) Spychal, Edyta; Vyšvařil, Martin
    In this article, the physico-mechanical properties and hydration processes of cement pastes containing three additives are introduced. Cement was replaced with pumice, trass, waste chalcedonite powder at 30% by mass and a combination of pumice or trass and waste chalcedonite powder in the amounts of 15% each. The main aim of this research was to assess the properties of two- or three-component binders to save cement in these binders. Rheological properties such as consistency, yield stress, viscosity and thixotropy were determined, in addition to porosity, 7-day and 28-day flexural and compressive strength and bulk density. Additionally, the heat evolution and degree of hydration of the tested pastes were compared. The use of all additives resulted in a reduction in the consistency of the tested pastes. The highest compressive strength measured after 28 days was observed for the cement paste with a 30% content of waste chalcedonite powder, which is related to it having the best pozzolanic activity of the materials used. The results of this research have confirmed that pumice, trass and waste chalcedonite powder can be used as components of blended Portland cements.
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    Denitrification assays for testing effects of xenobiotics on aquatic denitrification and their degradation in aquatic environments
    (MDPI, 2023-07-11) Pastorek Pániková, Kristína; Weigelhofer, Gabriele; Bílková, Zuzana; Malá, Jitka
    We developed, tested, and optimized two laboratory denitrification assays for both managers and scientists to assess the effects of xenobiotics on the denitrification process over 7 days (short batch assay, SBA) and 28 days (long semi-continuous assay, LSA). The assays facilitate (1) measuring the efficiency of nitrate removal under the influence of xenobiotics, (2) determining the removal of the tested xenobiotics via adsorption or biotic decomposition, and (3) testing the influencing parameters for optimizing the denitrification process. The adsorption of the xenobiotics was assessed by inhibiting all biological processes through the addition of HgCl2. Our tests demonstrate that the ratio of the initial nitrate concentration to the amount of bioavailable organic matter provided is essential to avoid organic carbon or nitrate limitation. While a pH less than 7 resulted in decreased denitrification, a pH more than 8 let to nitrite accumulation, indicating incomplete denitrification. Over durations of more than a week, weekly replenishments of the nitrate and HgCl2 and weekly purging with argon gas to reduce the oxygen concentrations are needed. The assays provide information about the accumulation of xenobiotics in the bioreactors that is necessary for the environmentally friendly treatment of the bioreactor fillings and provide insight into the potential of the bioreactors to remove pesticides from polluted water resources.
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    The behavior of terbuthylazine, tebuconazole, and alachlor during denitrification process
    (MDPI, 2023-10-01) Pastorek Pániková, Kristína; Bílková, Zuzana; Malá, Jitka
    Pesticide compound can influence denitrification processes in groundwater in many ways. This study observed behavior of three selected pesticides under denitrifying conditions. Alachlor, terbuthylazin, and tebuconazole, in a concentration of 0.1 mL L-1, were examined using two laboratory denitrifications assays alachlor; terbuthylazine; tebuconazole; inhibition; laboratory denitrification assays: a "short" 7-day and a "long" 28-day test. During these tests, removal of pesticides via adsorption and biotic decomposition, as well as the efficiency of nitrate removal in the presence of the pesticides, were measured. No considerable inhibition of the denitrification process was observed for and of the pesticides. On the contrary, significant stimulation was observed after 21 days for alachlor (49%) and after seven days for terbuthylazine (40%) and tebuconazole (36%). Adsorption was in progress only during the first seven days in the case of all tested pesticides and increased only negligibly afterwards. Immediate adsorption of terbuthylazine was probably influenced by the mercuric chloride inhibitor. A biotic loss of 4% was measured only in the case of alachlor.
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    Content changes of adsorbable organically bound halogens during sludge centrifugation and drying
    (Czech Academy of Agricultural Sciences, 2011-03-31) Hrich, Karel; Groda, Bořivoj
    The aim of this work was to calculate the material balance in the treatment process (centrifugation and drying). Control places were chosen and then samples of water and sludge (at the inlet and outlet of the system) were collected. The adsorbable organically bound halogens concentration was detected in these samples by the coulometric method.
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    Suitability of denitrifying woodchip bioreactor outflows for use in irrigation
    (Mendel University in Brno, 2017-11-08) Schrimpelová, Kateřina; Malá, Jitka; Bílková, Zuzana; Hrich, Karel
    The contribution is focused on aplication of denitrifying woodchip bioreactor outflow for irrigation of drained area.