## 3 Results and Discussion
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Parameter** & **Initial Sludge** & \begin{tabular}{c} **Natural** \\ **Deposition** \\ \end{tabular} & \begin{tabular}{c} **Accelerated** \\ **Aging** \\ \end{tabular} & \
\begin{tabular}{c} **Composing** \\ \end{tabular} &
\begin{tabular}{c} **Composing** \\ **with Zeolite** \\ \end{tabular} \\ \hline Humidity (W) [\%] & 65.21 & 68.12 \(\pm\) 2.29 & 49.85 \(\pm\) 2.37 & 63.74 \(\pm\) 3.04 & 68.84 \(\pm\) 4.09 \\ Ash content (ASH) [\%] & 31.59 & 50.2 \(\pm\) 2.9 & 38.19 \(\pm\) 1.34 & 45.11 \(\pm\) 2.56 & 46.58 \(\pm\) 1.24 \\ Ammonium [mg/kg] & 5.21 & 2.2 \(\pm\) 0.1 & 2.56 \(\pm\) 0.15 & 3.81 \(\pm\) 3.18 & 4.55 \(\pm\) 0.09 \\ Nitrate [mg/kg] & 4.84 & 2.87 \(\pm\) 0.14 & 3.19 \(\pm\) 0.26 & 3.18 \(\pm\) 0.08 & 3.19 \(\pm\) 0.09 \\ Anionic surfactants [mg/kg] & 0.99 & 0.51 \(\pm\) 0.01 & 0.60 \(\pm\) 0.08 & 0.09 \(\pm\) 0.02 & 0.10 \(\pm\) 0.01 \\ Total iron [mg/kg] & 119.01 & 99.39 \(\pm\) 4.2 & 118.69 \(\pm\) 4.35 & 113.97 \(\pm\) 8.38 & 117.39 \(\pm\) 4.9 \\ pH & 8.9 & 9.1 \(\pm\) 0.2 & 8.7 \(\pm\) 0.3 & 5.9 \(\pm\) 0.2 & 6.5 \(\pm\) 0.2 \\ Manganese [mg/kg] & 200.21 & 181.0 \(\pm\) 9.1 & 204.71 \(\pm\) 15.88 & 171.87 \(\pm\) 3.9 & 194.9 \(\pm\) 3.7 \\ Copper [mg/kg] & 26.32 & 22.55 \(\pm\) 1.6 & 26.86 \(\pm\) 1.79 & 25.12 \(\pm\) 0.98 & 32.97 \(\pm\) 2.36 \\ Petroleum products & 35.51 & 20.17 \(\pm\) 0.7 & 22.78 \(\pm\) 1.8 & 3.18 \(\pm\) 0.15 & 7.98 \(\pm\) 0.11 \\ \([\)mg/kg\(]\) & 12.33 & 10.73 \(\pm\) 0.7 & 12.30 \(\pm\) 0.94 & 12.03 \(\pm\) 0.61 & 15.06 \(\pm\) 0.68 \\ Aluminum [mg/kg] & 0.58 & 0.49 \(\pm\) 0.11 & 0.58 \(\pm\) 0.13 & 0.49 \(\pm\) 0.01 & 0.91 \(\pm\) 0.02 \\ Phosphorus (P\({}_{2}\)O\({}_{5}\)) [mg/kg] & 326.34 & 250.64 \(\pm\) 8.8 & 286.31 \(\pm\) 15.67 & 293.47 \(\pm\) 4.8 & 296.44 \(\pm\) 3.59 \\ Chromium [mg/kg] & 3.82 & 3.15 \(\pm\) 0.23 & 3.67 \(\pm\) 0.25 & 2.79 \(\pm\) 0.06 & 3.47 \(\pm\) 0.1 \\ Zinc [mg/kg] & 34.18 & 25.53 \(\pm\) 1.15 & 29.54 \(\pm\) 1.34 & 32.0 \(\pm\) 0.45 & 34.77 \(\pm\) 0.59 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Average characteristics of the samples. Figure 5: Boxplots for ash content in the samples. The highest degradation of organic matter occurred under natural conditions after 5 years of sludge deposition, which was attributable to intensive and prolonged biological processes. Over extended periods, microorganisms adapt to the sludge environment, and successive microbial communities decompose complex organic molecules into simpler compounds. Aerobic degradation occurs at the sludge surface, while anaerobic processes dominate deeper layers, leading to methane and carbon dioxide production. This prolonged activity results in significant organic matter reduction and increased ash content due to the accumulation of inorganic residues from mineralization. Composting resulted in a 15-17% increase in ash content while maintaining the potential for using the treated sludge as an organic fertilizer. The controlled aerobic conditions in composting accelerate the microbial breakdown of organic matter. The thermophilic temperatures reached during composting enhance the degradation of complex organic compounds, like lignin and cellulose. The mineralization process converts organic matter into inorganic substances, contributing to the ash content. Despite this increase, compost remains rich in nutrients essential for plant growth. The presence of zeolite marginally increased the overall mineralization of the sludge by 1.5-2.0%, which is unlikely to affect its efficacy as a fertilizer. Zeolites are microporous aluminosilicate minerals with high cation exchange capacities. When added to compost, zeolites can adsorb ammonium and other cations, potentially enhancing the microbial activity by providing a reservoir of nutrients. This can lead to a slight increase in the degradation rate of organic matter. However, this effect is marginal because the primary limiting factors in composting are usually moisture content and aeration rather than nutrient availability.