Nitrification of effluents: microbiological characterization

RESUMO

This work is concerned with the microbiological monitoring of nitrification processes carried out in two distinct continuous reactors submerse fixed-bed and airlift fluidized bad reactor. In the first case the system was operated using a synthetic effluent with variable salinity while in the second an actual petroleum refinery effluent was tested. On the basis of analys is for ammonia, nitrite and nitrate and nitrate at the inflow and outflow streams, system performance was evaluate. By inoculating appropriate solid medium, biotypes were isolated and colonies morphology was characterized. In general, colony of ammonia oxidizin bacteria (group 1) were round, initially transparent later, but becoming whitsh or phosphorescent. It took 36 to 48 hours for those colony to develop. The nitrite oxidizing bacteria (group 2) were generally white or redish-brown with colonies, developing time between 24 and 36 hours. In spite of the existence of various types of colonies, lamina observation under microscope revealed mainly Gram (-) bacilli with varied size. Typical width X length for individual bacterium cells were as follows 1 X 1,5mm for group 1, normally arranged in chains, and 0,5 X 1,0mm for group 2, generally shaped as small aggregates.