This article presents a reliability analysis of 166 full-scale wastewater treatment plants operating in Brazil, comprising six different treatment processes usually adopted. A methodology developed by Niku et al (1979) is used for the determination of the coefficients of reliability (COR), in terms of the compliance of effluent BOD, COD, TSS, TN, TP and FC to discharge standards. The design concentrations necessary to meet the prevailing discharge standards and the expected compliance percentages have been calculated from the coefficients of reliability obtained. The results showed that few plants, under the observed operating conditions, would be able to present reliable performances in terms of compliance with the analyzed standards. For all constituents and systems, the variability of the effluent quality was very large.
Effluent quality; reliability; performance evaluation; wastewater treatment technologies
