Remoção biológica de matéria orgânica e nutrientes de esgotos sanitários utilizando reatores em bateladas seqüenciais

Abstract

In recent years there has been a rapid deterioration in water quality due to the disposal of large amounts of nutrients, especially nitrogen and phosphorus, which are described as the major responsible for the phenomenon of eutrophication. In order to minimize the impacts with the release of these nutrients, this study investigated the performance of two sequencing batch reactors on removal of organic matter and nutrients in sewage. The reactors were constructed of glass with a volume of 12,6 L and treated 12,6 L / day of raw sewage in three batches of eight hours. The reactor 1 (RBS1) was operated with sludge age of 10 days and the reactor 2 (RBS2) with sludge age of 7 days. The operation of the reactors was divided into 4 phases: in phases 1 and 2 it was inoculated a sludge with SSV concentrations of 2470 mg.L and in phases 3 and 4 it was inoculated a sludge with SSV concentrations of 1800 mg.L - 1 , in both reactors. Phases 1 and 3 were characterized as a period of acclimatization of phases 2 and 4 respectively. The physical and chemical parameters monitored were: pH, alkalinity, the fractions of solids, total COD, filtered COD, nitrogen compounds, total phosphorus and orthophosphate. Beyond this, it were also performed in stage 4 respirometric tests associated with laboratory analysis to check the phosphorus release and the consumption of organic material in anaerobic environment and the absorption of phosphorus in aerobic environment. The results showed that the reactors were efficient in removing organic matter in all stages. Regarding to the removal of TKN, the reactors had almost the same behavior in phases 2 and 4, with its efficiencies of around 93% and 96% for rbs1 and 96% and 94% for RBS2 respectively. The removal efficiency of ammonia was similar in the reactors, with an average of approximately 95% in phases 2 and 4. The biological phosphorus removal showed an average efficiency of 91% of total phosphorus and 89% of orthophosphate in phase 1 of rbs1, and in the other phases did not exceed efficiencies of 70%. It was also observed in respirometric tests associated with laboratory analysis that it is possible to occur phosphorus release and denitrification in the anaerobic zone simultaneously, when there is presence of OAF and soluble biodegradable material.