845-454-8171 Menu

What Is IFAS, and How Does It Work?

By: Tom Frankel
Post Date: March 30th 2022

Post Tags:

What Is IFAS, and How Does It Work?

Integrated fixed film activated sludge (IFAS) is an innovative wastewater treatment technology that offers several advantages over conventional activated sludge technologies. IFAS involves adding an attached growth media to an activated sludge tank to facilitate biomass growth and strengthen the treatment process. The media added may be either fixed or free-floating. An IFAS system can be installed as an upgrade to an existing facility or as a new construction.


Table Of Contents

  1. How Does IFAS Treatment Work?
  2. Parts of an IFAS System
  3. Pros and Cons of IFAS
  4. Media Types Used for IFAS
  5. IFAS vs. Conventional Activated Sludge 
  6. Differences Between IFAS and MBBR
  7. Operation and Maintenance of IFAS Systems
  8. Is IFAS Right for Your Application?
  9. Work With a Professional IFAS Wastewater Treatment Company


How Does IFAS Treatment Work?

The IFAS treatment process combines conventional activated sludge and biofilm technologies in one reactor. While an IFAS system will vary in components, a typical IFAS configuration is similar to that of an activated sludge plant, involving introducing biomass carriers into specific zones within the activated sludge process.

This setup results in two different biological populations that act synergistically. The mixed liquor suspended solids (MLSS) degrade the majority of the organic load, and the biofilm establishes a strong nitrifying population that enables the oxidation of the nitrogenous load. Biofilm processes enable the anaerobic, aerobic and anoxic zones to exist together in one stage, and IFAS systems enable the additional biological population to be on a fixed surface, which means it’s no longer necessary to increase the suspended growth population.

Parts of an IFAS System

An IFAS system provides similar benefits to conventional activated sludge solutions while joining these technologies into a single reactor. While an IFAS system may vary in components, a typical configuration is similar to an activated sludge plant.

Within an IFAS system, biomass carriers are introduced to the system in select zones located within the activated sludge process, allowing two biological populations to work together. IFAS anaerobes and aerobes travel through a clarifier through the IFAS process.

Whether or not an IFAS system is based on fixed or dispersed media, it requires proper preliminary treatment design, implementation and operation. Fine screening or primary clarification helps prevent material buildup and ragging on the media in the aeration basin and dispersed media clogging. IFAS operational activities need to be performed by educated, trained and skilled professionals.

Pros and Cons of IFAS

Some of the advantages of using IFAS include:

While an IFAS system is highly efficient, there are certain aspects of the system you should be aware of:

Media Types Used for IFAS

The media types used for IFAS fall into two main categories: dispersed media that is spread throughout the aeration basin and fixed media that is fixed in place in the aeration basin.

Dispersed media types include:

Fixed-in-place media types include:

Dispersed media offers the advantages of exceptional mixing and a high surface area. Another advantage of dispersed media is that it is self-cleaning, requiring little to no backwashing as long as substantial agitation is permitted.

In addition to being cost-effective, fixed media systems are easy to install and do not result in material losses. Fixed media may also provide more efficient nitrification in colder climates, and the biomass may be more resistant to hydraulic shock loads.

IFAS vs. Conventional Activated Sludge

IFAS and conventional activated sludge systems are similar, but some major differences include the combination of aerobic, anaerobic and anoxic zones and the increased sludge retention time in IFAS.

Because fixed film wastewater treatment systems typically require less volume than conventional activated sludge systems, they tend to involve less capital cost. New IFAS systems typically cost less than new conventional activated sludge systems, and adding IFAS technology to existing activated sludge systems can avoid the costs of expanding the system’s capacity.

Differences Between IFAS and MBBR

MBBR stands for moving bed biofilm reactor, a wastewater treatment technique that is similar to IFAS. MBBR involves the use of a reaction tank that contains a plastic carrier combined in water or a mixture of water and sludge. The main difference between MBBR and IFAS is that the activated sludge from sludge recirculation is also used in IFAS. This means carrier-fixed biofilms and activated sludge are both used in one reaction tank.

Operation and Maintenance of IFAS Systems

IFAS systems have complex, highly mechanized configurations. Properly operating these systems requires expertise, so a trained professional needs to operate them at all times.

Proper maintenance also requires technical expertise. To prevent ragging and material buildup on the media and retaining screens, primary clarification or fine screening is necessary. If system parts need replacement, they will need to be ordered, as they are not typically available locally. Power system maintenance is also essential, as the system will fail in the event of a power outage.

Is IFAS Right for Your Application?

IFAS technology is suitable for both new constructions and upgrades to existing plants in both municipal and industrial wastewater facilities. Using fixed film aeration technology enables smaller tank sizes, and these tanks need to be designed for the incorporation of dispersed or fixed media. If dispersed media is used, additional auxiliary screens are often required.

When used to enhance existing plants, IFAS systems increase treatment capacity without requiring an increase in tank volume. Before installing an IFAS system in an existing plant, assess its aeration capacity to ensure it can handle the increased biochemical oxygen demand (BOD) removal and biomass respiration that results from the enhanced treatment performance that IFAS provides. Media installation also requires careful planning to ensure the basins can properly accommodate the chosen media.

Work With a Professional IFAS Wastewater Treatment Company

SSI Aeration, Inc. can provide IFAS wastewater treatment solutions for both industrial and municipal treatment plants. We can help convert a conventional activated sludge system to an IFAS or MBBR system or provide an IFAS system for a new plant. We also offer a wide range of products as well as design, lab and field services and can use advanced simulation tools to help ensure installation success. Let SSI Aeration’s fully staffed engineering department help find the ideal solutions for your plant.

With customers in all 50 states and more than 70 countries, the team at SSI Aeration, Inc. has the knowledge and experience to help wastewater treatment projects succeed. Contact SSI Aeration, Inc. online or start a quote today to learn more.