Bactérias nitrificantes no biofilme de filtro biológico percolador do tipo aberto (FBPA) e sua relação com a remoção de nitrogênio amoniacal

Abstract

This study aimed to quantify ammonia-oxidizing bacteria (Nitrosomonas) and nitrite-oxidizing bacteria (Nitrobacter) in the biofilm of an open trickling biological filter (FBPA) and to evaluate their relationship with the nitrification of the effluent from a UASB reactor treating domestic sewage. In order to quantify the nitrifying bacteria present in the filter biofilm, the Most Probable Number (MPN) technique was applied. The effluents from the UASB reactor and the FBPA were monitored using the following parameters: ammoniacal nitrogen (N–NH₄⁺), nitrous nitrogen (N–NO₂⁻), and nitric nitrogen (N–NO₃⁻), determined according to the methodology proposed by APHA/AWWA/WEF (2005). The estimated abundance of Nitrosomonas ranged from 10⁴ to 10⁷ MPN/mL, while Nitrobacter values ranged from 10³ to 10⁷ MPN/mL throughout the 428 days of monitored operation. The reduction in ammoniacal nitrogen concentration and the increase in nitrite and nitrate concentrations in the FBPA effluent, together with the increase in biofilm formation, indicate the establishment of nitrification in its two stages (nitritation and nitratation). A more consistent nitrification process was observed during the second stage of FBPA operation. The increase in ammoniacal nitrogen removal is likely related to natural ventilation, which enhanced aeration within the filter due to the absence of lateral walls, as well as to changes in organic loading rates and the expansion of the filter volume.