The study implements the Weibull reliability theory and reliability coefficient (RC) to analyse the rural municipal wastewater treatment plant performance (WWTP), considering the removal of several pollution indicators covering organic compounds, suspended solids and bio-genes. Full-scale technical tests were carried out at a facility with an average throughput of 450 m3/d and analysis of the reliability of their removal, up to the maximum discharge levels, resulted as follows - the installation achieved 100% in the case of BOD5, COD and TSS, while only 10% for TN and 3% for TP. These results were confirmed by RC analysis amounted to 0.2 for BOD5 and TSS, 0.4 for COD, 1.8 for TN and 4.9 for TP, showing that for organics and suspended solids, the concentrations in the treated effluent did not exceed the normative values throughout the five years, however, the technology did not provide effective bio-genes removal, hence TN and TP concentrations remained below or equal to the normative values for 36 and 11 days per year, respectively.