Eficiência de um sistema de lagoas de estabilização em série no tratamento de esgotos domésticos no Nordeste do Brasil.

Abstract

In this work we present and discuss the results obtained during the period between March 1977 and May 1979, with a pilot system of five stabilization ponds in series, fed continuously to the domestic sewage of Campina Grande, built at the Experimental Station of Treatments Biological Sewage Systems - EXTRABES, Federal University of Paraíba - UFPB. This system was scaled according to parameters that provided each pond with a hydraulic detention time between 5 - 7 days. We found that this system was able to reduce nBG5 from 300 mg / l to less than 25 mg / l, and, more importantly, it was able to reduce the number of fecal coliforms from 4.01x10 / 100ml to less than 100/100 ml, which is the World Health Organization (WHO) standard for unrestricted irrigation (15). The efficiency of the system was compared with that described in the project proposal for stabilization ponds in hot climates, presented by Mara (8) in the technical report published in April 1975. The results obtained lead us to conclude that this project proposal was substantially verified. The kinetic model for the reduction of fecal bacteria in stabilization ponds presented by Marais $ Shaw (10), later completed by Marais (11) (1) (12), is summarized, and the results obtained are used to verify the experimental evidence of this model. For the complete series of ponds, we found that the values ​​of K = 2.33 day -1 (K) = 2.03 days *, respectively, for Fecal Coliforms and Fecal Streptococci, provided the best experimental correlations. , we provide new elements, which we hope will contribute to making the series stabilization ponds in Brazil as efficient and economical as possible. We know that for this purpose it is necessary to provide, according to the means available on the spot, all those factors which have a favorable influence on the performance of these lagoons.