Avaliação do desempenho de uma série longa de lagoas de estabilização, na remoção de matéria orgânica e coliformes fecais, tratando esgotos domésticos no Nordeste do Brasil.

Abstract

The objective of the research was to evaluate the performance of a long series of stabilization ponds, in the removal of organic matter and fecal coliforms. The pilot scale experimental system was fed with domestic sewage, and was located in the Catingueira neighborhood of the Sewage Treatment Plant (ETE), and operated by CAGEPA (Paraíba Sewage and Water Company). It consisted of 10 units, one anaerobic (A11), followed by a facultative pond (F26) and eight maturation ponds (M25 to M32). The monitoring of the system occurred from August 15 to December 19, 1991, with the series of ponds running at a total hydraulic holding time of 19 days. The research methodology consisted in the collection of raw sewage and effluent samples from all ponds of the series for the determination of pH, temperature, dissolved oxygen, chlorophyll a, Biochemical Oxygen Demand (BOD), Chemical Demand (COD) and fecal coliforms. The mean value of the volumetric organic load applied to the anaerobic lagoon (A11) of the series was 244g BODs / m31d (3664kg BODs / ha.d), and the organic matter removal expressed in BODs was 95.4% with a mean concentration of BODs of 11mg / l in the final effluent of the series. The percentage of fecal coliform removal by the system was 99.9991%, and corresponded to a mean concentration of 131 CF / 100 mL in the final effluent of the series. The results obtained demonstrated that the total hydraulic detention time exerts an important influence on the reduction of fecal bacteria. With the use of suitable projects, it is possible to obtain percentages around 50% of land savings, with the implementation of long systems of stabilization ponds treating domestic sewage in tropical climates.