Enrichment of AOB and NOB Population by Applying a BABE Reactor in an Activated Sludge Pilot Plant

This paper deals with the effect of a bioaugmentation batch enhanced (BABE) reactor implementation in a biological nutrient removal pilot plant on the populations of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB). The results of fluorescence in situ hybridization (FISH) technique showed that AOB and NOB populations were significantly enhanced, from 4 to 8% and from 2 to 9%, respectively, as a result of the BABE reactor implementation. Regarding AOB, the percentage of Nitrosomonas oligotropha was mainly increased (3 to 6%). Regarding NOB, Nitrospirae spp was greatly enhanced (1 to 7%). Both species are considered K-strategist (high affinity to the substrate, low maximum growth rates) and they usually predominate in reactors with low ammonium and nitrite concentrations, respectively.