IFAS System Increases MLSS, Sludge Retention Time

Brentwood offers the complete AccuFAS Integrated Fixed-Film Activated Sludge (IFAS) system and provides process design assistance and engineering support to ensure optimum performance. The AccuFAS system consists of media modules combined to build media towers within an aeration basin. These media towers are typically 8 to 10 ft in height, 8 ft long and span with width of the basin. The media towers are supported by Brentwood’s pre-engineered AccuPier support system and secured to anchors in the concrete floor of the tank. Each assembly spans the width of the aeration tank in order to prevent bypassing of the mixed liquor.

Because of the critical relationship between the aeration and media in an IFAS system, Brentwood often provides an in-basin aeration package as part of the complete AccuFAS IFAS system. Diffusers mounted below the module structure provide aeration and distributed airlift pumping of wastewater through the media system. The number of diffusers will vary according to the location within the basin to account for the expected oxygen requirement profile. Diffusers are not placed in the area between the media assemblies to facilitate mixed liquor circulation.

Clarifier solids loading limitations put an upper limit on the amount of biomass that can be carried in the suspended growth system. IFAS systems allow for the additional bacterial population to exist on a fixed surface, thereby eliminating the need to increase the suspended growth population.

IFAS systems can increase the effective mixed liquor suspended solids (MLSS) in an aeration basin by as much as 3,000 mg/L. The additional biomass can offset the need for additional aeration basin capacity. The fixed biomass increases the sludge retention time, promoting better nitrification compared to simple suspended growth systems. During cold weather and where lower compliance limits are imposed, the added biomass improves the performance of nitrifying plants, or even allows non-nitrifying plants to nitrify.