Análise de eficiência e confiabilidade em sistemas de baixo custo de tratamento de esgotos do tipo lagoas de estabilização

• Autor(a) principal: Silveira, Ana Gláucia Magalhães
• Data de Publicação: 2011
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal do Ceará (UFC)
• Texto Completo: http://www.repositorio.ufc.br/handle/riufc/4766
• topic: Saneamento; Águas residuais - Purificação

The present work aimed to analyze the performance, reliability and operational situation of stabilization ponds located in Fortaleza and its Metropolitan Region. The reliability was assessed by using the Coefficient of Reliability (COR) and the performance was assessed by using descriptive statistics, removal efficiency and percentage of compliance with the discharge limits. Finally, operational diagnostics of the Wastewater Treatment Plants (WTP) was carried out from field inspections. Eight stabilization ponds were selected and the analyzed data corresponded to the period from January 2007 to March 2011. The most important parameters were studied and analyzed over the period assessed: pH, COD, filtered COD, BOD, filtered BOD, DO, TSS, settleable solids, ammonia, total coliforms and E.coli. Shape verification of the frequency distribution for the treated sewage indicators BOD, COD, TSS, ammonia and E. coli was conducted in two stages. This verification consisted of adherence tests to normal, lognormal, gamma and exponential tests of compliance with normal distributions by using the chi-square (χ2) and Kolmogorov-Smirnov tests. The graphical test "Probability - Probability Plot" was used in some cases to verify the theoretical distribution that best fit the sample data. The computer programs used to perform the tests were Statistica 7.0 and Statgraphics Centurion XV. WTPs performances with regard to the parameters pH, filtered COD and filtered BOD was not very significant. However, the parameters DO, TSS, ammonia and E. coli showed a clear superiority of the type ANA + FAC + MAT. Regarding efficiency, the best results were verified for this configuration, which, for having a higher number of treatment units, also showed a higher stability. In the operational diagnostics, the most relevant aspects observed may indicate that the ponds were silted or needed to have the sludge dredged, which interfered in the TDH or they would be organically overloaded, which directly impaired the reliability, efficiency and performance of the studied WTPs. The adherence tests showed that most of the evaluated parameters followed a lognormal distribution, especially those with higher amounts of data. For all parameters, there was a great variability in terms of CV and COR, and there was not an evident correlation between the values of COR and treatment types. In relation to the discharge limits, there was also a superior performance of the ANA + FAC + MAT treatment type and a low non expected performance for the FAC type, showing a poor treatment when compared to other types of stabilization ponds.