## 1 Introduction
The thermal, water, and air regimes of the soil improve, along with the biological activity [26]. A significant contribution of organic compounds to the soil occurs through the increased soil biomass from the addition of biological solids [27]. This is associated with improved soil moisture retention and reduced susceptibility to water and wind erosion, as well as enhanced fertility due to increased nutrient content. However, the elevated levels of heavy metals, biogenic elements, and potentially toxic substances in wastewater sludge require continuous monitoring of the composition and characteristics of the sludge, as well as calculations of permissible application rates. Furthermore, ongoing oversight of the application of composted sludge is necessary to ensure qualitative changes on agricultural lands [28]. [PERSON] et al. [29] analyzed methods for extracting nitrogen from wastewater sludge for the production of nitrogen-containing fertilizers. To intensify this process, the introduction of hydrothermal carbonization technology was proposed, which facilitates the disinfection of sludge prior to its further application, including fertilizer production. This process occurs at temperatures ranging from 180 to 300 \({}^{\circ}\)C under anaerobic conditions and steam pressure, catalyzing subsequent biochemical processes. [PERSON] et al. [30] addressed the comprehensive issue of wastewater sludge disposal in China. Based on an analysis of current technologies, the authors concluded that treated sludge should be used in areas remote from human activities. Furthermore, it is noted that most studies on this topic are of a short-term nature. To draw more reliable conclusions, long-term observations of treated soils are necessary. A similar study was conducted by [PERSON] et al. [31], who analyzed the effects of using treated wastewater sludge and established that it poses no risk to human health. The application of these fertilizers significantly increased the fertility indices of arid soils and enriched the structural abundance and diversity of the soil microbial population, while also enhancing the diversity and abundance of bacteria involved in the carbon cycle. As evidenced by various studies, different results emerged regarding the safety of using treated wastewater sludge as fertilizer for soil enrichment. This research examined an improved composting method for urban wastewater sludge by assessing the changes in sludge characteristics before and after the treatment. Composting dewatered sludge is a relatively simple technological process with low capital investment, and has been well-studied to date [32]. The composting of sewage sludge is a biological aerobic process that transforms organic waste into a stable, humus-like material suitable for use as a soil amendment. This transformation is facilitated by a diverse consortium of microorganisms, including bacteria, fungi, and actinomycetes, which decompose organic matter under controlled environmental conditions. The composting process not only stabilizes organic matter but also reduces pathogenic microorganisms, eliminates offensive odors, and decreases the moisture content of the sludge. The primary mechanisms driving composting involve the metabolic activities of microorganisms that break down complex organic compounds into simpler molecules, such as carbon dioxide, water, and ammonia. This degradation process is exothermic, releasing heat that elevates the temperature of the composting mass. The composting process can be delineated into three distinct phases: the mesophilic phase (25-40 \({}^{\circ}\)C), where readily degradable substrates are consumed; the thermophilic phase (45-70 \({}^{\circ}\)C), characterized by the breakdown of more resistant compounds, like cellulose and lignin, and significant pathogen reduction; and the maturation phase, during which the compost stabilizes and humification processes predominate [32; 33].