ANTIBIOTICS, ANTIBIOTIC RESISTANT BACTERIA AND ANTIBIOTIC RESISTANCE GENES – EMERGING POLLUTANTS IN SURFACE WATERS AND ANTHROPOGENICALLY INFLUENCED WATERS

Zvezdimira Tsvetanova, Dimitar Dimitrov, Hristo Najdenski

Abstract. The growing antimicrobial resistance of pathogenic bacteria is considered as one of the main threats to human and animal health. Despite the association of the problem mainly with clinical pathogens, there is growing evidence of a relationship with anthropogenic influence on the water. The review examines the prevalence of antimicrobial resistance among microbiomes in drinking, surface and wastewater and water-related biofilms, and summarizes available data on the content of antibiotics, antibiotic-resistant bacteria and resistance genes as pollutants of growing importance to aquatic ecosystems.

Keywords: antibiotics; antimicrobial resistance; antibiotic resistant bacteria; antibiotic resistance genes; natural waters; wastewater

THE STUDY OF THE GAS EXCHANGE FUNCTION OF LUNGS VIA THE MATHEMATICAL MODEL OF THE FUNCTIONAL RESPIRATORY SYSTEM

Tetiana  Semchyk,  Iryna Korniush, Vira Hovorukha, Oleksandr Tashyrev

Abstract. Respiratory system diseases are among the most dangerous for human life. Pathologies of the respiratory system appear due to environmental pollution, the spread of epidemics, etc.. To predict the course of pathological processes, the body's response to various influences of external extreme conditions, there is a strong need to develop the imitational mathematical models, which can provide the opportunity for the fast selection of the necessary optimal breathing mode. The goal of the work was to develop the imitational mathematical model to prognose and regulate the state of the respiratory system of the organism under the indignation of the environment. To study the mechanisms of self-regulation and adaptation of the body to disturbances of the external or internal environment, a mathematical model of the functional respiratory and circulatory system was developed. The dynamics of the partial pressures and stresses of the respiratory gases in the structures of the body was described by a system of ordinary differential equations. The principles of material balance and continuity of the flow were used to construct them. The structure of the model considered several reservoirs of the alveolar space, each of which was connected to the environment by a separate section of the airways and was washed by the corresponding volume of blood in the pulmonary capillaries. On the basis of the mathematical model of the functional respiratory system, an imitational mathematical model of the gas exchange process in the lungs has been developed and investigated. The model took into account the role of the elasticity and the resistance of the lung structures in the formation of the nature of the gas exchange process under various modes of external respiration. The results of the research will allow to accelerate the selection of the optimal breathing mode to achieve a stable balance of the internal and the external environment of the body.

Keywords: imitational mathematical modeling, the elasticity and the resistance of the lung structures, the gas exchange

 

CARBON-BASED CATHODE CATALYSTS USED IN MICROBIAL FUEL CELLS FOR WASTEWATER TREATMENT AND ENERGY RECOVERY

Reneta Boukoureshtlieva, Toma Stankulov, Anton Momchilov

Abstract. In the past 20 years Microbial fuel cells (MFCs) have been extensively studied regarding the possibility of transforming organic waste directly into electricity. There are significant differences between MFCs and conventional low temperature Fuel Cells (FCs), which make MFCs attractive: biotic catalyst at the anode; the anodic fuel is complex organic waste; MFCs operate under mild reaction conditions (neutral pH, temperature and pressure), close to ambient levels as optimum.

Like chemical fuel cells, MFCs are composed of anode and cathode. Oxygen is an ideal electron acceptor for MFCs because of its high redox potential, availability, and sustainability. However, the Oxygen Reduction Reaction (ORR) is kinetically sluggish, resulting in a large proportion of potential loss. Also, working conditions are quite different because of the type of complex media in which MFCs operate. In order to overcome these limitations, catalysts are often used to lower the overpotentials and accelerate the kinetics of the oxygen reduction reaction. One of the main challenges is the development of efficient and stable cathode catalysts for MFCs. By far, Pt and Pt-based catalysts (PGMs) have been extensively used, due to their catalytic efficiency in gas-diffusion electrodes. But the high cost and low durability have significantly lowered their utilization in MFCs.

A variety of non-precious metal catalysts have been developed for MFC applications including carbon-based catalysts, carbon supported composite catalysts, Me-based catalysts and biocatalysts. It is supposed that the ORR catalyst used for wastewater treatment in MFCs is simple to synthesize, cost-effective, durable after long-term operation in wastewater, tolerant to poisoning and able to restore catalytic activity after cleaning. In this regard carbon-based catalyst may be the most promising candidate for practical applications. This study reviews different carbon-based ORR catalysts for MFC applications for wastewater treatment and energy recovery.

Keywords: Carbon-based ORR catalysts, Microbial fuel cells, wastewater treatment.

BIOCARBON FROM DIFFERENT BIOMASS PRECURSORS

Kalina Miteva, Georgi Georgiev, Ivanka Stoycheva, Nartzislav Petrov, Bilyana Petrova, Andrei Sarbu, Boyko Tsyntsarski

Abstract: Thermochemical conversion of lignocellulosic biomass is considered as a good opportunity to obtain liquid raw materials for biofuels and biochemicals. During this pyrolysis process a solid product, biocarbon, is obtained. Nowadays there is a growing interest in biocarbon, due to the potential benefits of its application in soil as a stimulant and CO₂ trap. The physicochemical and porous properties of biocarbon are suitable for development of effective and inexpensive sorbents for the removal of contaminants from water. Biocarbon has promising sorption properties for various pollutants in water, including polycyclic aromatic hydrocarbons and heavy metals. Banana and orange peels, as well as cocoa flakes, were used as precursors. The carbonization was carried out at temperatures from 500 ° C to 900 ° C. Some of the samples were subjected to physical and chemical activation. The obtained carbon adsorbents are characterized by adsorption of iodine, BET, etc. It is planned to study the possibilities for the successful application of the obtained carbon materials as adsorbents for water and air purification, catalysts, hydrogen depots, etc.

TWO-STAGE ANAEROBIC DIGESTION OF ORGANIC WASTES: A REVIEW

I. Simeonov, L. Kabaivanova, E. Chorukova

Abstract. Anaerobic digestion is a biotechnological process, in which microorganisms degrade the complex organic matter to simpler components under anaerobic conditions to produce biogas and fertilizer. This process has many environmental benefits, such as green energy production, organic waste treatment, environmental protection and greenhouse gas emissions reduction.

It has long been known that the two main communities of microorganisms (acidogenic and methanogenic) taking part in the anaerobic digestion differ in many aspects e.g. their optimal conditions for cell growth and development. Therefore, the anaerobic digestion in a single bioreactor (BR) (single-phase process) required selected optimal conditions, taking into account the slow-growing methanogens at the expense of fast-growing acidogens, which affects the efficiency of the whole process. This has led in recent years to development of two-stage anaerobic digestion, in which the processes are divided into a cascade of two separate BRs. It is known that this separation of the processes into two consecutive BRs leads to significantly higher energy yields for the two-phase system (H₂ + CH₄), compared to the traditional single-stage CH₄ production process.

The present paper aims to review the literature in the field of two-stage anaerobic digestion of organic wastes.

Keywords: two-stage anaerobic digestion, hydrogen, methane, mathematical models

APPLICATION OF THE PLASMA FOCUS DISCHARGE IN THE RADIOBIOLOGY STUDIES

Orlin Gemishev, Stanislav Zapryanov, Vasilii Gol’tsev, Bojidar Galutsov, Alexander Blagoev

Abstract. The purpose of this short review article is to present the results of the influence of the ionizing X-ray pulses of plasma focus on living organisms, by performing experiments in vivo and analyzing changes in some vital characteristics of the objects, such as survival ability, efficiency of photosynthesis of unicellular organisms at moderate doses (up to 65 mSv); efficiency of enzyme production, change in protein content and change in fungi mass in the radiation dose range 7 mSv ÷ 45 Sv; changes in mammalian blood characteristics and appearance of signs of anemia due to the significant dose load.

Keywords: Plasma focus, X-ray radiation, radiobiology studies

THE EUROPEAN GREEN DEAL AND THE FORESTS IN THE WORLD

Alexander H. Alexandrov, Ivan Iliev

Abstract. The Green Pact of the European Union is part of the United Nations' programme of sustainable development to 2030. To implement this pact, it is necessary to transform the European Union's economy with a view to protect and restore endangered and damaged natural ecosystems, sustainably use resources, and improve people's health status. For this purpose, it has been envisaged to stabilize climate by reducing the emissions of greenhouse gases by 55% up to 2030, as compared with their levels of 1990. Changes are necessary in emission trade, land use and forestry. Forests are particularly important for realizing the Green Pact because of their multi-functionality. The following, most general inferences can be made about the world forests intended to perform their resource-providing, environmental and social functions:

- The world area of forests has continued diminishing in the recent 10 years by 4.7 million ha per year as an average as the rate of forest loss has been abating due to the expansion of the forests in Asia and Europe. The deforestation for the period from 2015 to 2020 occurred at the rate of 2 million ha per year with a trend as to abatement.

- The forests in Africa are the most vulnerable ones, in terms of their area, as their reduction already surpasses that in South America. The deforestation in South America from 2010 to 2020 decreased to the half of that in the period 1990-2000 and 2000-2010.

- Sustainable forest management requires contemporary forest-management planning and forestry but, only for half of their total area there are forest-management plans. This planning activity has been carried out almost completely in Europe only, whereas its proportions in terms of forest area are 2/3 – in Asia, 1/2 – in North and Central America, and only 1/3 – in Oceania, 1/4 – in Africa and 1/6 – in South America. Without total forest-management planning, it is impossible to realize the multi-functional, sustainable management of forests.

- The proportions of forests for harvesting timber and non-timber products, for preservation of the soil and water, for conservation of the biodiversity, and for social benefits and other purposes, in the particular continents, have not been sufficiently well-founded scientifically, hence. the need for optimizing these in congruity with the human needs determined in consideration with the on-going climate changes and the current socioeconomic factors.

- The European Green Deal is, to a certain extent, a continuation of previous polices partly formulated in the last decades of the 20-th century and improved by means of modern philosophy and technology suggesting a new approach to reasonable taking of what is sufficient while harvesting resources.

Keywords: European Green Pact, World forests