This paper assesses the environmental impact of the wastewater treatment plant (WWTP) of the Cameroon Real Estate Company (CRE) camp in the "Cité-Verte" district in Yaoundé (Cameroon) and the causes of its malfunction. The study was carried out in two stages. The first stage consisted of describing the wastewater treatment steps of the WWTP, and analyzing the staff interviews in order to determine the causes of malfunction that had been suspected. The second phase consisted of collecting water samples at the entry of the WWTP (P1), inside the WWTP (P2), and at the outlet of the WWTP (P3). This, in order to produce a list of the WWTP's collecting systems, characterize the various types of wastewater (P1 and P2) and the treated wastewater (P3), and then determine the effect of effluent discharges on the environment. Finally, the structural and operational malfunctions of WWTP are identified using the Ishikawa and the Pareto diagrams. The results of water characterization show that the mean values of pH (7.7), EC (1059.3 μS/cm), TDS (524.6 mg/L), T° (23.6 °C), BOD5 (10.8 mg/LO2), NO3- (2.3 mg/L), and fecal coliforms (447.3 CFU/100 mL) are below the acceptable limit values of the Cameroonian standard of treated wastewater discharge. However, the mean values of TSS (269.3 mg/L), PO4
3- (1661.6 mg/L), K+ (1220.6 mg/L) and Escherichia coli (10133.3 CFU/100 mL) exceed the recommended values set by the Cameroonian standard of treated wastewater discharge. The values of the wastewater parameters at the sampling point P3 are globally lower than those at the sampling point P1 but higher than Cameroon’s standard for PO4
3- and K+. These results demonstrated that the current system (filters and plants) is appropriate but not optimal. The Pareto diagram reveals that the inadequate plant controls, unfavorable working conditions, lack of maintenance and
systematic control, and outdated equipment represent 20% of the causes responsible for 80% of the WWTP's malfunction. Therefore, the implementation of corrective and preventive measures is essential for better monitoring and determinization of the optimal performance of the WWTP of the CRE camp in the "Cité-Verte".