Reviviscence of aerobic chemoheterotrophic bacteria in an activated sludge pilot plant after a prolonged absence of oxygen

The effect of the absence of oxygen (anoxia followed by prolonged anaerobiosis) on the dynamics and reviviscence of populations of aerobic chemoheterotrophic bacteria has been studied in the activated sludge of a pilot plant fed with a synthetic substrate (Viandox). The majority of the bacteria were Zoogloea, Alcaligenes and Pseudomonas, accounting for 65% to 85% of the cultivable species. Most of these bacteria are reviviscent after eight days of anaerobiosis, their relative proportion remaining practically unchanged. The protozoa and metazoa usually present in the sludge disappear over the first three days of absence of oxygen, to be replaced by species of the class Diplomonadida, an anaerobic phylum. In a pure culture, the Zoogloea and Alcaligenes strains from the pilot sludge remain reviviscent after 8 days without oxygen, but much less than in the pilot plant.