Performance evaluation and coefficients of reliability for waste stabilization ponds in northeast Brazil

  • Matheus Sales Alves Departamento de Engenharia Hidráulica e Ambiental (DHEE). Universidade Federal do Ceará (UFC), Rua do Contorno, s/n, Bloco 713, CEP: 60451-970, Fortaleza, CE, Brazil.
  • Fernando José Araújo da Silva Departamento de Engenharia Hidráulica e Ambiental (DHEE). Universidade Federal do Ceará (UFC), Rua do Contorno, s/n, Bloco 713, CEP: 60451-970, Fortaleza, CE, Brazil.
  • André Luís Calado Araújo Diretoria de Recursos Naturais. Instituto Federal de Educação, Ciência e Tecnologia do Rio Grande do Norte (IFRN), Avenida Senador Salgado Filho, n° 1559, CEP: 59015-000, Natal, RN, Brazil.
  • Erlon Lopes Pereira Departamento de Engenharia Hidráulica e Ambiental (DHEE). Universidade Federal do Ceará (UFC), Rua do Contorno, s/n, Bloco 713, CEP: 60451-970, Fortaleza, CE, Brazil.
DOI: https://doi.org/10.4136/ambi-agua.2571
Keywords: effluent quality, reliability, waste stabilization ponds

Abstract

This paper assesses the reliability of Waste Stabilization Ponds (WSP) and proposes an alternative approach to WSP design based on the calculation of coefficient of reliability (COR) from an acceptable measure of violation of discharge standards. For that, data were collected from 10 full-scale systems operating in Northeast Brazil. All systems receive predominantly domestic effluent and are composed of one facultative pond and two serial maturation ponds. Different levels of restriction for effluent discharge were considered regarding the parameters: BOD, COD, total suspended solids, ammonia and thermotolerant coliforms. The Log-normal Probability Distribution Function (PDF) was able to represent the behavior of the concentration data in the effluent and, therefore, allowed the COR calculation. The COR was obtained from the coefficient of variation (CV) of the concentrations and the standardized normal variable associated with a 95% probability of non-exceedance. The observed dispersion of the results proved to be detrimental to the adoption of a single COR value for the evaluated parameters. In addition, the comparison between observed and design/operational concentration for optimal performance showed that the 95% reliability scenario represents a less achievable target for WSP systems.


Published
26/01/2021
Issue
Vol. 16 No. 1 (2021)
Section
Papers

Authors maintain the copyrights for their work. However, they grant rights of first publication to Ambiente e Agua - An Interdisciplinary Journal of Applied Science. In compensation, the journal can transfer the copyrights, allowing non-commercial use of the article including the right of sending the article to other data bases or publication media. The journal uses the CC BY 4.0 license"