Nitrogen removal assessment through nitrification rates and media biofilm accumulation in an IFAS process demonstration study

An IFAS demonstration study was conducted at the 76,000 m3/day (20MGD) James River Wastewater Treatment Plant (JRTP) located in Newport News, Virginia by converting one fully-aerobic conventional aeration basin with dedicated secondary clarification to a 7041 m3/day (8404 m3/day max month) IFAS train in a modified Ludzack-Ettinger (MLE) configuration. During the study, biomass concentrations on the biofilm carriers were monitored (weekly) as well as nitrogen species concentrations in the IFAS reactor to quantify the nitrogen transformations occurring within the demonstration tank. In a related effort, nitrification kinetics for ammonia and nitrite oxidizing bacteria were monitored on a weekly basis for IFAS media alone, IFAS process mixed liquor without media, and IFAS mixed liquor and media together in an effort to identify the location of nitrification activity (i.e. on the media or in the suspended culture) in the IFAS process. Biomass quantity on the media was generally observed to be inversely related to temperature except during a period when an auxiliary carbon source contaminated with fungi was introduced. Both ammonia oxidizing and nitrite oxidizing bacterial activity were elevated on the carriers compared to the suspended culture (AOBmedia: 4.97 mgNOx/gMLSS/hr; AOBsuspended: 1.72 mgNOx/gMLSS/hr; NOBmedia: 7.55 mgNOx/gMLSS/hr; NOBsuspended: 0.82 mgNOx/gMLSS/hr) during all periods of the study. In-basin nitrification rates calculated based on nitrogen profiling efforts averaged 0.90 mgNOx/m2/day which was in good agreement with the average of 0.89 mgNOx/m2/day for IFAS mixed liquor and media from batch testing.

► Effluent TN averaged 12 mg/L during an IFAS demonstration using an MLE configured process train.
► The activities of both AOB and NOB were elevated on the IFAS carriers compared to the MLSS.
► NOB activity was greater on media relative to MLSS compared to AOB activity between media and MLSS.
► Biomass density and nitrification activity on media were homogenous throughout aeration basin.