Analysis of organic pollution impact on purification capacity at the Tanjero River in Sulaimani City

The Tanjero River in Sulaimani City exhibits severe pollution, prompting a comprehensive water quality analysis. Physical and chemical characteristics were conducted to evaluate their contribution to contamination levels. The primary objectives of this study were to assess the degree of water quality deterioration and to evaluate the purification capacity of the river. Utilizing the Thomas graphical method, the maximum concentration of organic mass entering from the city’s wastewater leading to oxygen depletion was observed in location 2, with the ultimate biochemical oxygen demand L_o 214.89 mg L⁻¹ which exceeds the allowed limit with a deoxygenation rate k₁ of 0.52 d⁻¹. Furthermore, the Streeter-Phelps model was employed to assess the river’s behavior under continuous flow conditions, focusing on dissolved oxygen deficits and reaeration dynamics. The results demonstrated that the DO values of the river water were less than the common minimum DO required for aquatic life 4 mg L⁻¹. The maximum deficit of dissolved oxygen for the water river was too high 20.31 mg L⁻¹ based on t_c = 1.46 d, and the reaeration rate constant k₂ is 1.58 d⁻¹. Dissolved oxygen deficiencies were observed to be markedly elevated beyond location 2, indicating a constrained self-purification capability of the river and presenting a significant risk to aquatic life. This research is crucial for an international audience as it underscores the global challenges urban rivers face in managing organic pollution and maintaining ecological balance. It highlights the need for effective wastewater management practices and global strategies. Therefore, establishing a wastewater treatment facility in the city is suggested as an effective and feasible measure to prevent further deterioration of the river’s water quality.