The inefficiency of wastewater treatment plants (WWTP) for the removal of pollution has devastating effects on human health, negative impacts on the environment, and unfavorable consequences for economic activity. The activated sludge process is extensively used for wastewater treatment across the globe, especially in Algeria. While the purification performance and reliability of this process have been established, various types of biological malfunctions can occur. Our objective is to provide practical guidance in identifying these malfunction types. The evaluation of a wastewater treatment plant's (WWTP) malfunction degree is a crucial step in assessing its purification performance. This study aims to evaluate the operational performance of a textile industry WWTP situated in our region. The study focused on the wastewater treatment plant (WWTP) at the DENITEXT textile complex in Sebdou, Western of Algeria. The performance of the plant was analyzed with the help of the Analytical Hierarchy Process (AHP), a method that considers all criteria impacting that have an impact on the malfunctioning of the WWTP's malfunction and their relative importance. To evaluate the dysfunction score and the operational status of the treatment plant, a hierarchical multicriteria analysis (HMA) was used.The value of the SDG (Score Dysfunction Global), evaluates the performance of the WWTP in treating effluent, obtained 1.50, which falls within the range of [0, 2], indicates that the treatment plant is in a dysfunctional state but poses no present or future risks. The purpose of this work is to assist plant managers in effectively managing the wastewater treatment process of the plant. Currently, there are no known or potential risks.