EFFECTS OF AERATION CYCLES ON POPULATIONS OF NITRIFYING BACTERIA AND NITROGEN REMOVAL IN INTERMITTENTLY-AERATED REACTORS

Biological nutrient removal relies on different groups of nitrifying bacteria, which convert ammonia to nitrate or nitrite, and denitrifying bacteria, which convert nitrite or nitrate to nitrogen gas. The key to efficient, robust biological nitrogen removal processes relies on knowing the microorganisms involved and how they respond to different operating conditions. Intermittently aerated reactors can provide appropriate environmental conditions to support growth of microorganisms performing nitrification and denitrification. Previous research has shown that high nitrogen removal efficiencies can be achieved in these reactors (Cheng and Liu, 2001), with the added benefits of lower aeration costs and lower alkalinity and space requirements. In the present study, we assessed the effect of aeration cycles on the performance and the populations of nitrifying bacteria in intermittently aerated reactors treating swine wastewater. Specifically, we investigated how long non-aeration periods can be without negatively affecting ammonia removal, and how aeration-cycle affects nitrifying bacterial populations.