Ecological Engineering and Environment Protection

Svetla Marinova¹, Elena Zlatareva¹, Nicholas Kathijotes²
¹Institute of Soil Science, Agrotechnologies and Plant Protection “N. Pushkarov”, Sofia, Bulgaria
²Cyprus Institute of Technology, Cyprus
Abstract. Information is presented on the principles of organic farming, which is based on the dynamic relationship between soil, plants, animals, humans, and the environment. The main goal of the organic farming system is to support the natural cycles of life without harming nature. The main principles for the sustainable development of organic farming and the strictly regulated forms of sustainable farming, which cover the criteria for ecological production to the highest degree, are indicated. A characteristic of organic farming is given, with the concept of soil as a biological system taking center stage. Approaches to the organic production system are presented, as well as the advantages and disadvantages of organic farming.
Keywords: organic farming, approaches, advantages and disadvantages of organic farming.

doi.org/10.32006/eeep.2025.2.0913
ECOLOGICAL ENGINEERING IN REGENERATIVE AGRICULTURE
Alexander Sadovski
Institute of Soil Science,Agrotechnologies and Plant Protection, Sofia, Bulgaria
Abstract: The creation of the three well-known companies engaged in Environmental Engineering is being tracked. The report aimed to present applications of ecological engineering methods to Regenerative Agriculture. Three examples are given: First – development of Decision Support System to help irrigated crops growers. Second - The project “Synergism – key to sustainable Agriculture” in the Institute of Soil Science,Agrotechnologies and Plant Protection, Sofia, Bulgaria. The result is development of the scientific basis of a new Innovative approach for fertilization and irrigation of agricultural crops in a changing climate for sustainable agriculture. Third - Australian Net Zero Institute and University of Sydney are examining the exploration, extraction, and processing of critical mineral resources. The medium-to long-term focus of the Net Zero Institute is on recycling critical materials in end-of-life products and substituting critical materials in new products. Results of these projects clarify the importance of ecological engineering methods for Circular Solutions in ecology.
Keywords: ecological engineering, fertilization, irrigation, regenerative agriculture, synergism

doi.org/10.32006/eeep.2025.2.1419
APPROACHES FOR RESTORING THE FERTILITY OF CONTAMINATED SOILS IN THE SREDNOGORIE REGION

Viktor Kolchakov, Elena Zlatareva, Svetla Marinova

Institute of Soil Science, Agrotechnologies and Plant Protection "N. Pushkarov", Sofia, Bulgaria

Abstract: A large number of factories were built on the territory of Bulgaria in the 1960s and 1970s. In some areas, heavy metal pollution greatly worsened soil fertility. This is the case with the soils in the area of the Copper Mining Plant in the Srednogorie region. A significant part of the surface horizons of the soil is acidified to a very high degree and has an exchangeable acidity that is toxic to plants. Some of the studies are presented, which establish that acidification and accumulation of copper is mainly in the surface layer of the soil and in the zone of mechanical displacement up to 30 cm. Vegetation experiments were carried out with arable and subsoil from the "Gradinite" area. Indicator crops are corn, alfalfa, turnips and peas. 3 precise field experiments were also carried out, in which the influence of various land improvement agents was tested - manure, ash, phosphorization and mineral fertilization. Technological solutions have been developed to restore the fertility of contaminated soils in the area of the Copper Mining Plant in the Srednogorie region – through a combination of chemical reclamation and mechanical displacement of the layers, chemical and biological reclamation of contaminated soils and for heavily eroded and skeletal soils.

Keywords: pollution, Copper mining plant, vegetation and field experiments, technologies

doi.org/10.32006/eeep.2025.2.2043

MODELLING OF THE ANAEROBIC DIGESTION OF ORGANIC WASTES IN CONTINUOUSLY STIRRED TANK REACTORS – A REVIEW

I. Simeonov

Institute of Microbiology, Bulgarian Academy of Sciences, Sofia, Bulgaria

Abstract. Anaerobic digestion (AD) is an effective biotechnological process for treatment of different agricultural, municipal and industrial wastes. However, it is a very unstable process in regard to the biogas reactors operation. This is due to the complicated interactions between different microbial species as well as of the complex transformations of the organic matter affected by a variety of environmental factors. The most common reactor type used for AD of wastewaters is the continuously stirred tank reactor (CSTR). AD is a process carried out by microorganisms that is widely used to convert various organic wastes into bioenergy (hydrogen and methane-rich biogas) and nutrient-rich digestate (natural fertilizer). AD of organic waste mixtures (AcoD) offers several advantages such as better biodegradation and process stability, while increasing biogas yield due to synergistic effects. However, the operation of effective AD and AcoD processes requires a full understanding of important operating parameters.

Use of mathematical models is a powerful tool for investigations and optimisation of the AD. A large number of papers in the field of the mathematical modeling of AD are known. On the basis of such models, monitoring systems (software sensors) and automatic control of the AD processes have been theoretically developed. However, most of them are very complicated and difficult to implement in industry. Recently, artificial intelligence (AI) has emerged as an innovative approach to the computer modelling and optimization of AD and AcoD processes. Compared to conventional methods and models, AI-based algorithms have made modelling these processes much easier. Various AI algorithms, including multivariate statistical analyses, tree-based machine learning, nature-inspired optimization, support vector machine, and artificial neural networks (ANNs) have been widely used to model the AD processes.

This paper reviews the current state of the art in the AD in CSTR modelling and identifies the key areas that require further research endeavours. This review discusses AI applications for AD process modeling as well. A critical comparison is made with some of the popular mathematical models and algorithms for monitoring and optimization designed on their basis. The review presents also future research directions in this area.

Keywords: anaerobic digestion, anaerobic co-digestion, CSTR, mathematical modelling, deterministic models, artificial intelligence, machine learning, artificial neural networks

doi.org/10.32006/eeep.2025.2.4453

NONLINEAR ADAPTIVE FAULT-TOLERANT CONTROL FOR LPV TIME-DELAY PE M FUE L CELL SYSTEMS

Abdel Aitouche ¹ and Haoping Wang ²

¹Junia, CRIStAL UMR 9189, Universit´e de Lille, 59655 Villeneuve d’Ascq, France

²LaFCAS Laboratory, Automation School, Nanjing University of Science and Technology, China

Abstract: This paper addresses the design of an active Fault-Tolerant Control (FTC) strategy for Polymer Electrolyte Membrane Fuel Cell (PEMFC) systems exhibiting time-delay characteristics. An adaptive observerbased approach is proposed using a Linear Parameter Varying (LPV) model and Unknown Input Observer (UIO) techniques to estimate actuator faults and generate residuals. The proposed method leverages Linear Matrix Inequality (LMI) conditions to ensure the stability and convergence of the observer in the presence of parameter variations and delays. The fault estimation and control law are integrated to compensate for faults such as compressor mass flow and return manifold orifice deviations. Simulation results validate the robustness and efficiency of the control strategy under various fault scenarios.

Keywords: Fault tolerant control, Fuel cell systems, Time delay systems, LPV, UIO

doi.org/10.32006/eeep.2025.2.5462
DYNAMICS OF CHANGES IN PROPERTIES OF CINNAMONIC FOREST SOILS INFLUENCED BY FOREST FIRES IN SOUTHWESTERN BULGARIA
Simeon Bogdanov¹, Gauhar Baubekova², Pavel Pavlov¹¹University of Forestry-Sofia, Bulgaria
²A. Baitursynuly Kostanay regional university, Kostanay, Kazakhstan

Abstract. The forest fires are very common in the territory of Bulgaria, especially in cases of long summer droughts. They represent one of the most significant challenges in forest management, both from an economic and silvicultural perspective. The implementation of reforestation measures aimed at restoring destroyed forest ecosystems necessitates comprehensive studies on the changes in soil composition and properties. This paper presents results from a study on the dynamics of changes in the composition and properties of Cinnamonic Forest soils (Chromic Luvisols) affected by wildfires in Southwestern Bulgaria. The research examines changes in total carbon content, total nitrogen, pH levels, and the C/N ratio. The diverse nature of the factors influencing the dynamics of soil property alterations following wildfires underscores the need to investigate the consequences in each specific case of forest fire

Keywords: forest fire, soil properties, Luvisols.

doi.org/10.32006/eeep.2025.2.6372
EFFECT OF CLIMATIC AND HYGIENE FACTORS ON THE HEALTH STATUS OF ELEPHANTS BRED IN ZOOS

Andreas Antoniou ¹^{,
2}, Teodora P. Popova ²
¹Attica Zoological Park, At Yalou, Spata 19004, Athens, Greece
²Faculty of Veterinary Medicine, University of Forestry, Sofia, Bulgaria
Abstract. Elephants are vital to their ecosystems, acting as keystone species and ecosystem engineers that help maintain biodiversity and ecological balance. Their presence and behavior significantly influence the structure of their ecosystems. They help maintain the balance of different plant and animal species, enriching biodiversity. In the present article, the importance of elephants for nature and humans in the areas they inhabit is reviewed. The main anatomical and behavioral features of elephants and the specific care for them in zoo breeding are presented. In this aspect, a survey of the conditions and care for elephants in the zoos in Sofia and Athens was carried out. The importance of climatic factors in the respective regions was also highlighted. It was established that the conditions of breeding and care for the animals are maximally tailored to their characteristics and requirements, which is why the health status of all elephants bred in both zoos is very good. The cooperation between the zoos in Sofia and Athens is fruitful for the bringing up these exotic animals.

Keywords: elephant, biodiversity, ecological balance, zoo breeding, health status

doi.org/10.32006/eeep.2025.2.7378
IN VITRO EFFECT OF CHITINASE ON OVAL FUNGI
Teodora P. Popova, Alexander Aminev

Faculty of Veterinary Medicine, University of Forestry, Sofia, Bulgaria

Abstract. In vitro studies of the enzyme chitinase for inhibitory effect on oval fungi Sacharomyces cerevisiae and Candida albicans were performed in order to assess its prospect of practical application as an antimycotic agent. Antimycotic action against both examined species was established in studies conducted by the agar-gel diffusion method. Тhe effect enhanced with increasing the enzyme concentration (P<0.01) and the exposure time. After a two-hour exposure to chitinase of the tested oval fungi in suspensions with a density of 2x10⁶ CFU/ml, the decrease in their quantity was average 17.5%, after 4 hours – by 32.5%, and after 24 hours – almost twice.
Keywords: chitinase, oval fungi, antimycotic effect

doi.org/10.32006/eeep.2025.2.7984
Fractal Characterization of Bulgarian Relief Using DEM-Derived Contours
Rosen Iliev, Boyko Ranguelov

Space Research and Technology Institute, Bulgarian Academy of Sciences, Sofia, Bulgaria

Abstract: This study applies fractal analysis to characterize the topographic complexity of the Republic of Bulgaria using contour lines derived from a high-resolution Digital Elevation Model (DEM). The fractal dimension (FD), estimated via the box-counting method, serves as a quantitative indicator of spatial heterogeneity across different hypsometric belts and relief types. Results reveal an overall mean FD of approximately 0.784, with values increasing from lowlands through hills to mountain areas. Within the mountain belt, the low mountain zone (600–1000 m a.s.l.) exhibits the highest fractal dimension, while middle and high mountain zones show decreasing FD values. Minimum FD values display a narrow range, whereas maximum FD values fluctuate more broadly, indicating somewhat greater landscape fragmentation in certain areas. Spatial patterns of fractal dimension correspond closely with major tectonic features, including the Stara Planina mountain range and Eastern Rhodopes, where tectonic block boundaries coincide with elevated FD values. The northern part of Bulgaria, geodynamically stable, exhibits lower fractal dimensions compared to the more active southern regions. Additionally, the highest elevation areas tend to have the lowest FD values, attributed to their limited spatial extent and shorter contour line lengths. These findings contribute to a deeper geomorphological understanding of Bulgaria’s terrain and demonstrate the utility of fractal metrics in regional landscape analysis.
Keywords: Bulgaria, DEM, fractal dimension, contour lines, topography, GIS

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