Tomáš Vítěz

Production of biogas: relationship between methanogenic and sulfate-reducing microorganisms

Abstract The production of high-quality methane depends on many factors, including temperature, pH, substrate, composition and relationship of the microorganisms. The qualitative and quantitative composition of methanogenic and sulfate-reducing microorganisms and their relationship in the experimental bioreactors has never been studied. The aim of this research was to characterize, for the first time, the diversity of the methanogenic microorganisms and sulfate-reducing bacteria, and study their relationship and biogas production in experimental bioreactors. Amplification of 16S rRNA gene fragments was carried out. Purified amplicons were paired-end sequenced on an Illumina Mi-Seq platform. The dominant morphotypes of these microorganisms in the bioreactor were homologous (99%) by the sequences of 16S rRNA gene to the Methanosarcina, Thermogymnomonas, Methanoculleus genera and Archaeon deposited in GenBank. Three dominant genera of sulfate-reducing bacteria, Desulfomicrobium, Desulfobulbus and Desulfovibrio, were detected in the bioreactor. The phylogenetic trees showing their genetic relationship were constructed. The diversity and number of the genera, production of methane, hydrogen sulfide and hydrogen in the bioreactor was investigated. This research is important for understanding the relationship between methanogenic microbial populations and other bacterial physiological groups, their substrate competition and, in turn, can be helpful for controlling methanogenesis in bioreactors.

The effect of fertilisation with digestate on kohlrabi yields and quality

Three treatments were used in a two-year (2014–2015) vegetation pot experiment with kohlrabi of the cv. Moravia: (1) untreated control; (2) digestate; (3) digestate + phosphorus (P). The nitrogen (N) rate was the same in treatments 2–3. There were significant differences between years in all parameters. The weight of single kohlrabi bulbs in the unfertilised control was significantly lower in both years (33.1–46.9%) than in the digestate treatment (100%). Digestate supplemented with P (treatment 3) increased the bulb yield significantly by 11.0–14.3% compared with pure digestate (treatment 2). In both years the content of bulb nitrates (mg NO3 –/kg FM (fresh matter)) was significantly the lowest in the unfertilised control (135 and 163, respectively). After digestate applications the nitrates content (mg NO3 –/kg FM) increased significantly in both years, i.e. to 315–327 (2014) and to 486–509 (2015) compared to unfertilised control. In two years the content of ascorbic acid (mg/kg FM) did not differ among the three treatments (274–288 in 2014 and 311–329 in 2015). Digestates can be recommended for kohlrabi fertilisation prior to planting.

The diversity of sulfate-reducing bacteria in the seven bioreactors

Anaerobic technology has a wide scope of application in different areas such as manufacturing, food industry, and agriculture. Nowadays, it is mainly used to produce electrical and thermal energy from crop processing, solid waste treatment or wastewater treatment. More intensively, trend nowadays is usage of this technology biodegradable and biomass waste processing and biomethane or hydrogen production. In this paper, the diversities of sulfate-reducing bacteria (SRB) under different imputed raw material to the bioreactors were characterized. These diversities at the beginning of sampling and after cultivation were compared. Desulfovibrio, Desulfobulbus, and Desulfomicrobium genus as dominant among sulfate reducers in the bioreactors were detected. The Desulfobulbus species were dominant among other SRB genera before cultivation, but these bacteria were detected only in three out of the seven bioreactors after cultivation dominant.

A new combination of substrates: biogas production and diversity of the methanogenic microorganisms

Abstract Agriculture, food industry, and manufacturing are just some of the areas where anaerobic technology can be used. Currently, anaerobic technologies are mainly used for wastewater treatment, solid waste treatment, or for the production of electrical and thermal energy from energy crops processing. However, a clear trend is towards more intensive use of this technology in biomass and biodegradable waste processing and hydrogen or biomethane production. An enormous number of anaerobic digesters are operating worldwide but there is very little information about the effect of different substrate combinations on the methanogens community. This is due to the fact that each of the anaerobic digesters has its own unique microbial community. For the most effective management of anaerobic processes it would be important to know the composition of a consortium of anaerobic microorganisms present in anaerobic digesters processing different input combinations of raw material. This paper characterizes the effect of the input raw materials on the diversity of the methanogen community. Two predominant microorganisms in anaerobic digesters were found to be 99% identity by the sequences of the 16S rRNA gene to the Methanoculleus and Thermogymnomonas genera deposited in GenBank.

Effects of De-icing Salts on the Respiration of the Microorganisms of Activated Sludge

Winter road maintenance is particularly ensured using the application of chemicals on roads. Especially in urbanised areas, the solution of water with de-icing salts is discharged into sewer system transporting this water to wastewater treatment plant, where it can cause lot of problems. Beside the corrosive effects of salt on the materials used for sewer system and technological equipment of wastewater treatment plant, salt concentration affects the efficiency of biological wastewater treatment. The analyses performed with activated sludge from wastewater treatment plant showed that commonly used de-icing salts (NaCl, MgCl2, CaCl2) profoundly affected the respiratory activity of its microorganisms. Increasing concentrations of chloride in the influent of the wastewater treatment plant caused a progressive decrease in respiratory activity and a progressive prolongation of the acclimation period of the microbial community. The extent of the increase in the acclimation period was dependent on the examined road salt.

Study of rheological behaviour of wines

Abstract 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.

Determination of rheological behaviour of wine lees

Abstract This study deals with the rheological properties of wine lees. Samples of wine lees of the Saint Laurent variety were used in this experiment. The investigated wine lees arose in the process of production red grape wine in 2013 (Czech Republic). At first, the chemical background was determined. The chemical background includes the following chemical parameters: total acidity, pH, alcohol content, reduced sugars, free SO2, total SO2, and volatile acid. In the second phase of the study, physical properties were determined. Specifically, a sample of wine lees was subjected to rheological tests. These tests consisted in determination of dependence of dynamic viscosity on the temperature, hysteresis loop tests, dependence of dynamic viscosity on the time and step-down in the shear rate test. The experiment demonstrated that the dynamic viscosity increased with increased temperature – this phenomenon is caused by thermolabile proteins – and the wine lees has rheopectic behaviour; the degree of rheopexy was found to rise with the increasing temperature.

Condensing shafts on biogas stations and operational safety

This article investigates health and safety risks at a biogas station, in particular the activities in the condensation shaft. There were selected three scenarios in total, which can lead to a fatal accident during the maintenance and servicing of equipment located in the condensation shafts. These are the following scenarios: (1) the worker descends to the condensation shaft and in the subsequent service activities consumes oxygen contained in shaft, falls into unconsciousness and dies. (2) There is such a gas concentration in the condensate shaft that intoxication occurs (but even direct asphyxiation is possible—e.g., methane, carbon dioxide) thereafter subsequent death. (3) The worker suffers fatal injuries due to a fall from a height. The individual scenarios are discussed in the article, including whether and under what circumstances these may occur. To support the authors claims, measurements of selected gases concentrations were made in condensation shafts at eight biogas plants. The aim of this article is to highlight the risks that can be encountered when working in condensing shafts and how they can be prevented.

Novel insight into the process of nutrients removal using an algal biofilm: The evaluation of mechanism and efficiency

ABSTRACT Eutrophication of water by nutrient pollution remains an important environmental issue. The aim of this study was to evaluate the nutrient uptake capacity of an algal biofilm as a means to treat polluted water. In addition, the study investigated the nutrient removal process. The algal biofilm was able to remove 99% of phosphorus within 24 hours of P addition, with the PO4-P concentration in inflowing water ranging from 3 to 10 mg L−1. Different patterns of phosphorus and nitrogen removal were observed. Daily quantity of removed NO3-N ranged from 2 to 25% and was highly dependent on solar irradiance. Precipitation of phosphorus during the removal process was studied using X-ray diffraction analyses and was not confirmed in the biofilm. The biofilm system we constructed has a high efficiency for phosphorus removal and, therefore, has great potential for integration into wastewater treatment processes.