Desempenho operacional do módulo 2 da estação de tratamento de esgotos de mangabeira na grande João Pessoa.

Abstract

This study evaluated the operational performance of the Module 2 of the Sewage Treatment Plant of Mangabeira in the City of Joao Pessoa (7°10"South; 34°49"West), Paraiba state, northeast Brazil which was designed and initially operated with three reactors in series, being the first an aerated pond with complete mixture, followed by a facultative aerated pond and a maturation pond, but, nowadays, as a consequence of a new managing policy, it is made up of three stabilization ponds in series, being two anaerobic and a secondary facultative one. Samples of the influent raw sewage (EB) and effluents of the ponds anaerobic 1 (LAj), anaerobic 2 (LA2) and facultative (LF) were weekly collected during a period of eight months (between March and November 2005), having been analyzed the variables pH, BOD5, COD, dissolved oxygen, temperature, suspended solids, electrical conductivity, total alkalinity, total acidity, and the fecal indicator thermotolerant coliform. Algae and cyanobacteria biomass in terms of chlorophyll "a" was estimated only in samples collected from the effluents of both the second anaerobic and the facultative ponds. Influent flow-rate fluctuations were monitored and two studies on daily variation of variables in raw sewage and pond effluents were also carried out. Based on the flow-rate mean value of 35.52 1/s, the influent BOD5 mean value (264mg/L) and the geometric characteristics of the ponds the actual total hydraulic retention time of 28.41 days and the volumetric organic loading of 57.74gDB05/mJ.dia, for the first anaerobic pond, were estimated demonstrating that the treatment system is still operating underloaded. The analysis of monitoring data showed that the performance of Module 2 was similar to those of regional (Campina Grande and Guarabira) systems with nearly the same configuration. It was, also, demonstrated that from the point of view of the variables analyzed herein the design of two anaerobic ponds in series may improve the general performance of a series of ponds. Therefore, the adaptation of the reactors to a new configuration proved to be satisfactory, however the final effluent doesn't comply yet with the requirements for discharge into receiving water bodies.