Integrated Fixed-Film Activated Sludge (Ifas): The New Choice for Nitrogen Removal Upgrades in the United States

Johnson, Terry L.; McQuarrie, James; Shaw, Andrew

doi:10.2175/193864704784147214

Cited by 14 publications

(13 citation statements)

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“…IFAS allows plants to retro-fit and upgrade their existing plant without significant new construction, which lowers capital costs and does not require additional plant footprint area. IFAS also enables plants designed for partial nitrification, or plants needing to expand to meet a growing demand, to achieve complete, year round nitrification despite limiting cold temperature conditions with smaller aeration tanks and without increasing the solids load to secondary clarifiers (Johnson et al 2004;). …”

Section: One Of These Emerging Technologies Is Integrated Fixed Film mentioning

confidence: 99%

“…This is expected to be much longer than that required for nitrifier growth even at very cold temperatures. The addition of a fixed film media to an existing activated sludge process effectively increases the biomass in the aeration basin without placing any additional load on the secondary clarifier (Johnson et al 2004). By maintaining a low SRT in the IFAS basin, the process has also been credited with better settling sludge with lower SVIs compared with conventional activated sludge processes ).…”

Section: Process Descriptionmentioning

confidence: 99%

“…Typically, IFAS tanks hold anywhere between 30-60% fill by volume (Johnson et al 2004). It is not uncommon for the IFAS tank to be designed for a certain fill, but to operate at a lower media concentration until the additional media is needed at a higher future flow rates ).…”

Section: Process Descriptionmentioning

confidence: 99%

“…Randall et al (1996) also notes that the greatest improvement of nitrification capacity when compared to conventional activated sludge occurred at lower temperatures. Johnson et al (2004) notes that the IFAS process is also operated in the same way as conventional activated sludge processes by controlling DO and process SRT and requires the same amount of operator attention as a conventional activated sludge process. In many cases, an IFAS upgrade requires less aerobic volume, resulting in the creation of an anoxic zone preceding the aerobic zone with media to allow for more TN removal (Hubbell et al 2004).…”

Section: Benefits Of Ifasmentioning

confidence: 99%

“…By maintaining low process SRT and lower MLSS concentrations in the aeration basins, IFAS does not cause secondary clarifiers to become overloaded because the additional biomass remains in the IFAS tank. (Johnson et al 2004;) Secondary clarifier loading rates associated with the IFAS process are remarkably lower than conventional activated sludge processes ).…”

Section: Benefits Of Ifasmentioning

confidence: 99%

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Evaluation of Nitrification Kinetics for a 2.0 MGD IFAS Process Demonstration

Thomas¹,

Bott²,

Regmi³

et al. 2009

proc water environ fed

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The James River Treatment Plant (JRTP) operated a 2 MGD Integrated Fixed Film Activated Sludge (IFAS) demonstration process from November 2007 to April 2009 to explore IFAS performance and investigate IFAS technology as an option for a full scale plant upgrade in response to stricter nutrient discharge limits in the James River Basin. During the study, nitrification kinetics for both ammonia and nitrite oxidizing bacteria and plastic biofilm carrier biomass content were monitored on a near-weekly basis comparing the IFAS media, the IFAS process mixed liquor, and mixed liquor from the full-scale activated sludge process. Carrier biomass content is variable with respect to temperature and process SRT and relates to the localization of nitrification activity in the IFAS basin. Similar to trends observed for carrier biomass content (Regmi, 2008), ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) activity also shifted from the fixed film to the suspended phase as water temperatures increased and vice versa as the temperature decreased. The data suggest that AOB activity occurs on the surface of the biofilm carriers, while NOB activity remains deeper in the biofilm. During the highest temperatures observed in the IFAS tank, AOB activity on the media contributed as little as 30% of the total nitrification activity in the basin, and after temperatures dropped below 20 °C, AOB activity in the fixed film phase made up 75% of the total activity in the IFAS basin. During the warmest period of the summer, the media still retained more than 60% of the total NOB activity, and more than 90% of the total NOB activity during the period of coldest water temperature. This trend also points out that some AOB and NOB activity remained in the mixed liquor, even during the coldest periods. The retention of nitrification activity in the iii mixed liquor indicates that the constant sloughing of biomass off of the carriers allowed for autotrophic activity, even during washout conditions. Carrier biomass content and nitrification rates on the IFAS media remained constant along the length of the basin, indicating that the IFAS tank is will mixed with respect to biomass growth, although there was a concentration gradient for soluble species (NH 4 -N, NO 2 -N, NO 3 -N). In addition to the weekly nitrification rate measurements, experiments were also conducted to determine how operational inputs such as dissolved oxygen (DO) and mixing affect the nitrification rates. Mixing intensity had a clear impact on nitrification rates by increasing the velocity gradient in the bulk liquid and decreasing the mass transfer boundary layer mass transfer resistance. At higher mixing intensities, advection through the mass transfer boundary layer increased making substrate more available to the biofilm. The affect of mixing was much more profound at low DO, whereas increased mixing had less effect on nitrification rates at higher bulk liquid DO. DO also affected nitrification rates, such that as DO increased it penetrated deeper in...

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Section: One Of These Emerging Technologies Is Integrated Fixed Film mentioning

confidence: 99%

Section: Process Descriptionmentioning

confidence: 99%

Section: Process Descriptionmentioning

confidence: 99%

Section: Benefits Of Ifasmentioning

confidence: 99%

Section: Benefits Of Ifasmentioning

confidence: 99%

See 3 more Smart Citations

Evaluation of Nitrification Kinetics for a 2.0 MGD IFAS Process Demonstration

Thomas¹,

Bott²,

Regmi³

et al. 2009

proc water environ fed

View full text Add to dashboard Cite

show abstract

A Modeling and Simulation Study of the Role of Suspended Microbial Populations in Nitrification in a Biofilm Reactor

Mašić

Eberl

2013

Bull Math Biol

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Many biological wastewater treatment processes are based on bacterial biofilms, i.e. layered aggregates of microbial populations deposited on surfaces. Detachment and (re-)attachment leads to an exchange of biomass between the biofilm and the surrounding aqueous phase. Traditionally, mathematical models of biofilm processes do not take the contribution of the suspended, non-attached bacteria into account, implicitly assuming that these are negligible due to the relatively small amount of suspended biomass compared to biofilm biomass. In this paper, we present a model for a nitrifying biofilm reactor that explicitly includes both types of biomass. The model is derived by coupling a reactor mass balance for suspended populations and substrates with a full one-dimensional Wanner-Gujer type biofilm model. The complexity of this model, both with respect to mathematical structure and number of parameters, prevents a rigorous analysis of its dynamics, wherefore we study the model numerically.Our investigations show that suspended biomass needs to be considered explicitly in the model if the interests of the study are the details of the nitrification process and its intermediate steps and compounds. However, suspended biomass may be neglected if the primary interests are the overall reactor performance criteria, such as removal rates. Furthermore, it can be expected that changes in the biofilm area, attachment, detachment, and dilution rates are more likely to affect the variables primarily associated with the second step of nitrification, while the variables associated with the first step tend to be more robust.

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