Attached growth
SAFF — Submerged Aerobic Fixed Film
An aerobic attached-growth process in which biomass develops on submerged fixed media.
Overview
What is SAFF?
Submerged Aerobic Fixed Film (SAFF) is an attached-growth biological wastewater-treatment process in which microorganisms grow on fixed media submerged in an aerated tank. Air supplied beneath the media provides oxygen for the biofilm, which treats the wastewater as it passes through. SAFF is often considered for compact and packaged sewage treatment plants, depending on the influent and the complete treatment train.
A submerged aerobic fixed film reactor uses structured media fixed in place beneath the water surface. Air diffused below the media supplies oxygen to the biofilm that grows on it, which in turn treats the wastewater passing through.
With media fixed in place, SAFF can be configured for smaller plants and packaged units where an attached-growth process is appropriate. Operating requirements still depend on the influent and the complete treatment train.
How the process works
The SAFF process flow.
A typical sequence. Stages are configured for each plant's wastewater and treatment objectives.
01
Screening & equalisation
Screens remove solids and a balancing tank evens out the incoming flow.
02
Fixed-film reactor
Wastewater passes through submerged media colonised by aerobic biofilm.
03
Aeration
Diffusers beneath the media supply oxygen and keep the reactor mixed.
04
Settling
Excess biomass is separated from treated water in a settling stage.
05
Filtration & disinfection
Final polishing prepares water for discharge or reuse.
Key characteristics
What sets SAFF apart.
Low maintenance
Fixed media mean no carriers to retain and fewer moving parts.
Stable biomass
Biofilm stays in place, giving dependable day-to-day performance.
Compact
Well suited to packaged and containerised plant designs.
Simple to operate
Suitable for sites with limited operator availability.
Typical Applications
Where SAFF is typically considered
- Residential
- Commercial
- Hospitality
- Educational institutions
- Laboratories
- Containerized sewage treatment
Selection factors
When SAFF may be evaluated
- The installation is small to medium in size.
- A packaged or containerised plant is preferred.
- Low maintenance and simple operation matter most.
Relevant solutions
Solutions SAFF can form part of.
A named technology is one part of a treatment train. Its role is confirmed through water analysis, process design and the required outcome.
Related technologies
Other technologies that may be evaluated.
Wastewater Treatment
Moving Bed Biofilm Reactor
Attached-growth biological treatment using carrier media that provide surface area for microorganisms while moving within the reactor.
Process family · Attached growth
Typical use · Sewage and industrial wastewater needing robust treatment and operational flexibility
Explore
Wastewater Treatment
Extended Aeration
An activated-sludge process using extended aeration periods for stable biological treatment.
Process family · Activated sludge / batch
Typical use · Sewage treatment plants needing a relatively robust biological process
Explore
Wastewater Treatment
Sequencing Batch Reactor
A biological process in which treatment stages occur sequentially within the same reactor through controlled operating cycles.
Process family · Activated sludge / batch
Typical use · Variable flows where batch-cycle operation offers process flexibility
Explore
Technology selection
Is SAFF right for your site?
Technology selection depends on the wastewater, the space available and the treated-water objective. Share what you know about your requirement and our engineering team can help compare the options.