Assessment of partial nitrification achieved by real-time aeration duration control through microbial population shift using FISH and SEM

Abstract:

The shift of nitrifier population within a partial nitrification reactor was investigated using fluorescence in-situ hybridization(FISH) techniques and the floc morphology was observed using scan electron microscope(SEM).Partial nitrification to nitrite was achieved quickly by using real-time aeration duration control when domestic wastewater was treated in a lab-scale sequencing batch reactor(SBR).The average nitrite accumulation ratio was above 93%.The morphology photographs observed using SEM indicated that the sludge showed a shift towards spherical and small rod-shaped clusters from the diverse morphology.FISH analysis showed that ammonia-oxidizing bacteria(AOB) gradually out-competed nitrite-oxidizing bacteria(NOB).AOB population percentage increased from 3.5%(during the start-up period) to 8.5%(after achieving nitritation for 102 days),while NOB population percentage decreased from 3.1% to less than 0.5%.Accordingly,the long-term operation with the use of real-time aeration duration control was not only favorable for AOB community optimisation,but also for the achievement of partial nitrification in practice.