Submerged aerated filter (SAF) sewage treatment plants

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Utilising proven submerged aerated filter (SAF) technology, the Rewatec SAF range of sewage treatment plants provide the ideal solution for larger applications.

Rewatec SAF sewage treatment plant

What is a submerged aerated filter (SAF)?

The Rewatec submerged aerated filter (SAF) is a robust, GRP, wastewater treatment plant that combines energy efficiency with a low carbon footprint.

Uniquely engineered to cater for a population of 25 to 600+ PE, the Rewatec SAF is perfect for both small and large scale projects where access to the main drainage system is unavailable, or if treatment in situ is required.

By using biological treatment within the SAF, a range of on-site applications can be achieved. This includes a final effluent quality of 20mg/L BOD, 30mg/L SS and up to 5mg/L NH4-N. It can also achieve up to 62% total nitrogen (TN) removal and up to 50% total phosphorus (TP) removal. For applications where additional nitrogen and/or phosphorus removal is required, a Rewatec DSAF can be provided. Dosing options are also available to improve both TN and TP removal.

Side section cutaway view of a Rewatec SAF sewage treatment plant

Example applications 

  • residential developments
  • hotels and inns
  • leisure facilities 
  • camping and caravan sites
  • restaurants and cafes
  • schools
  • office buildings 
  • industrial sites

Adaptable to suit your needs

The Rewatec SAF range of sewage treatment plants can be tailored to meet your exact needs. 

Size variations

Our range of Rewatec SAF plants can be configured to suit your site and population requirements. This includes single tank, two tank and three tank systems, as well as bespoke schemes for larger projects.

Rewatec kiosks

All Rewatec SAF plants are supplied with a robust kiosk to house the electronic and mechanical componentry required to operate the system. Key features include:

A optional variable speed blower

  • reduces energy usage
  • reduces energy costs
  • reduces your businesses carbon footprint

A single of three phase blower

  • single phase is standard on all tanks up to 125 PE. Three phase is optional
  • three phase is standard on all tanks from 150 PE and above

An optional dissolved oxygen probe

  • automatically reduces the air supply (and therefore power) if the plants occupancy is reduced
  • maximises energy efficiency 
  • reduces ongoing running costs
Rewatec Kiosk for a sewage treatment plant

How do our Rewatec SAF systems work?

The Rewatec SAF sewage treatment plants form three treatment stages: primary settlement, biological treatment (biological and aeration zone) and final settlement. Flow through all of the treatment stages from inlet to outlet occurs via gravity, integral airlifts or via pumps.

Primary settlement tank

In typical installations, wastewater first flows into a primary settlement tank, allowing liquids to separate from suspended solids. The primary settlement tank is also designed to accommodate flow and load fluctuations.

Biological and aeration zone

Inside the Rewatec SAF, micro-organisms grow on floating biofilm media. They feed on organic wastewater pollutants, producing effluent composed of biomass particles and treated wastewater.

Our plastic biofilm media are specifically shaped to increase the surface area on which micro-organisms grow. This maximises their ability to treat wastewater and helps to minimise the size of the reactor (and therefore overall footprint of the plant).


Biomedia used in a Rewatec SAF

A diffuser system feeds oxygen from blowers in the kiosk to promote the growth of the biomass. Bubbles from the aeration continuously mix the contents of the Rewatec SAF to ensure optimal contact between wastewater and micro-organisms, improving their ability to remove wastewater pollutants (such as ammonia or organic matter). To optimise efficiency, all of our SAF products come with a steel painted kiosk as standard.

Final settlement tank

After treatment, wastewater flows into the final settlement tank. Solids accumulate at the bottom of tank before being redirected to the primary settling area by a re-circulation pump (enabling partial nutrients removal). The treated wastewater (final effluent) is subsequently discharged from the SAF via the outlet pipe.

Rewatec SAF servicing and maintenance

Routine maintenance and servicing of the Rewatec SAF is recommended to help preserve the lifespan of the system. If the tank is well maintained, the lifecycle of the product can exceed 90 years (i.e. the same as the GRP material).

You can find out more information about our personalised sewage treatment plant maintenance and servicing packages here.

Obtain a free quote for our services

We stand by our products

For over 50 years, we have proudly developed sustainable and long-lasting products that make a real difference for our customers, our professional partners, and, above all, our planet.

Our experience in the industry allows us to give you a complete 25 year warranty for our Rewatec SAF sewage treatment plants and a 12 month warranty for our kiosks.

Rewatec 25 years warranty

CPD training course

Our 45-minute CPD certified course "An introduction to off-mains wastewater management" is ideal for Architects, Consultants, Engineers, Installers and Specifiers looking to learn more about what wastewater treatment is and why it is important, regulatory bodies and the current UK regulations, how systems are designed, and what systems are available.

Request a CPD course

Options and accessories

Personalise your Rewatec SAF plant to meet your site requirements, with our wide range of options and accessories.

Options and accessories for Rewatec SAF, DSAF and MBBR sewage treatment plants

Technical information

Designed, manufactured and tested in accordance with EN12566-3 for plants below 50PE, EN12255 for plants above 50PE and the British Water Code of Practice for Flows and Loads, the Rewatec SAF is capable of meeting strict effluent standards that exceed UK environmental discharge requirements, for a range of on-site applications that don’t have access to the main sewage network. 


Rewatec SAF sewage treatment plant specification table

Available products

We offer a complete range of Rewatec SAF wastewater treatment plants to meet your needs. From 25 PE to 600+PE, wherever your site, whatever the regulations, we have the right product to transform any challenge into a tailor-made solution.

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