MONITORING OF NITRIFYING AND DENITRIFYING BACTERIA IN A SEQUENCE BATCH REACTOR TREATING DOMESTIC SEWAGE

Abstract

This study sought to evaluate the results obtained in the microbiological monitoring in a sequenced batch reactor (SBR) with immobilized biomass in bench scale (10 L) fed with effluent of an anaerobic fluidized bed reactor (AFBR) that treats domestic sewage of Campo Mourão, State of Paraná. SBR reactor was operated with cycle of 5,5 h and kept at controlled temperature of 35 °C during 210 days. The assays were carried out in order to do isolation and maintenance of nitrifying and denitrifying in accordance with the methodology proposed by Mendonça (2001) and estimation of the most probable number (MPN) of these organisms of interest in accordance with the methodology reported by Tiedje (1984). With the monitoring of the reactor, it was possible to observe results similar to those observed by Mendonça (2002) to domestic sewage as substrate in the feeding of a SBR reactor in relation to MPN (denitrification) and to morphologies observed in the optical microscopy. The estimation of MPN of denitrifying bacteria indicated significant values in all the samples, probably due to the characteristics of the domestic sewage used in the reactor feeding and to the low carbon/nitrogen ratio. In the microscopies, it was observed bacteria similar to Nitrosomas and Nitrobacter. However, it is necessary to carry out more detailed studies about the biomass stabilization, considering the relation among determined groups of microorganisms in the processes of nitrification and denitrification. Key words: Domestic Sewage. Nitrifying. Denitrifying. Immobilized Biomass. Nitrossomas. Nitrobacter.