Reatores de biofilme em bateladas sequenciais visando a nitrificação e desnitrificação simultâneas de esgoto sintético sob baixa relação carbono/ nitrogênio

Abstract

The worrying presence of nitrogen in wastewater is related to its potential to cause eutrophication in water bodies, in addition to the risks to human health. Simultaneous nitrification and denitrification (SND) is an innovative biological process for nitrogen removal, which minimizes the energy needed to supply oxygen and prevents the addition of an electron source. This process has been applied in batch systems, such as Sequential Batch Biofilm Reactor (SBBR), and some of their operational conditions have been tested for maximum removal along with time savings, carbon source and aeration. This work, which used synthetic sewage with low C/N ratio, was divided into tests, where batch reactors with polyurethane foam were evaluated with different concentrations of alkalinity and nitrogen tributaries. Each test followed 32 cycles of 6h (with aeration of 4.5h) and in this period analyzes were carried out to verify the environmental conditions, the carbon and nitrogen removal efficiencies as well as the evaluation of microbial adhesion. The environmental conditions indicated for the NDS process were maintained throughout the operation. With a mean C/N ratio of 5.3, a COD removal efficiency between 62 and 84% and NT removal of 14 to 34% was obtained. The nitrification and denitrification efficiencies obtained were low, but indicated that there was no limitation of the NDS process due to unavailability of electron donors. The unsatisfactory process is due to insufficient dissolved oxygen concentrations and / or aeration time. The increase of alkalinizing and of affluent nitrogen was not interesting, discouraging the removal of nitrogen. Finally, COD removal efficiency was shown by multiple regression, related to the affluent C / N ratio, while NT removal efficiency was strongly influenced by COD and alkalinity affluents.