Avaliação de sistemas biorremediadores em efluentes da lagoa facultativa da estação de tratamentos de esgotos em Mangabeira, João Pessoa/ PB

Abstract

One of the least efficient basic sanitation services in most cities in the Northeast of Brazil has been the sewage system, with little collection network and the inefficiency of sewage treatment systems, a condition that has contributed to a serious environmental problem, the eutrophication of the bodies water receptors. The sewage treatment usually occurs in stabilization ponds. However, treatment often does not meet the standard set by legislation. Macrophytes and biofilm have been considered efficient bioremediation in the removal of nutrients in eutrophic environments. Thus, the objective of this work was to test the use of these two bioremediation systems in effluents from the facultative pond of the Sewage Treatment Station (WWTP) in Mangabeira, João Pessoa-PB, to check the efficiency in the improvement of the quality of this treatment, guaranteeing effluents of better quality. An experiment was carried out in mesocosmos, three treatments (control, biofilm and macrophytes) with three replicates each, during 40 days. Samples were evaluated at the beginning of the experiment, on the 20th day and on the 40th day to check the physical and chemical parameters, and the phytoplankton and zooplankton community as indicators of water quality. The results showed little variation in the physical and chemical parameters between the different treatments, obtaining significant differences in the pH variant, in the following comparisons of treatments: control/macrophyte and biofilm/macrophyte, since the pH remained acidic in the treatment with macrophytes while in the other two (control and biofilm), the pH became basic. In addition, total transparency was verified in biofilm treatment and a decrease in nitrite levels, demonstrating greater efficiency of this bioremediation system in these variants. The treatment with macrophytes was more efficient in the removal of phosphorus and mineral salts, obtaining the lowest orthophosphate index and electrical conductivity. The contribution of phytoplankton classes between the control treatment and the bioremediators was distinct, with more Cyanophyceae in the control and more Chlorophyceae in the biofilm and macrophyte treatments. The zooplankton community present showed a significant inversion of species richness in the three treatments, initially contained a higher density of rotifers (indicator of eutrophic environments), and later presented a higher density of cladocerans, characterizing, therefore, the improvement in the quality of the effluent. From these results, it was possible to prove that the bioremediation systems can be used in WWTP. In this study, it was verified that the two biological systems of environmental recovery complement each other, the macrophytes being more efficient in the removal of nutrients (with the exception of nitrite) and biofilm being more efficient at reducing nitrite and cyanobacteria and increasing transparency. However, complementary studies must be carried out to estimate the amount of biofilm area and macrophyte biomass required for in situ bioremediation in stabilization ponds.