WPL Hybrid-SAF™

Submerged aerated filtration for wastewater treatment

The modular WPL Hybrid-SAF product range combines submerged aerated filter technology with the latest research to minimising the risk of compliance failures.

Product flexibility makes the modular plant suitable for a range of applications from sewage to industrial wastewater treatment. The site-specific design ensures energy efficiency and environmental compliance.

The SAF units can operate as an individual treatment plant or can be designed to connect in series to form a larger plant, which takes in to account the footprint of each individual site requirements.

WPL SAF plants have a proven track record of over 25 years in utilising submerged aerated filtration for wastewater treatment; compliant with WIMES, specific water utility asset standards, CDM regulations, European norms and directives.

Why you should choose the WPL Hybrid-SAF:

Flexible design

  • Scalable – the modular units can operate as an individual treatment plant or be designed to be connected in series to form a larger plant.
  • Reduced footprint – the modular units can be designed to fit sites with a small or unusual footprint or scalable to accommodate a growing population of up to 10, 000 PE.
  • Transportable – can be used as a moveable asset during site modification and used elsewhere if an existing installation becomes redundant before the end of its life. This prevents premature scrappage and reduces waste.


Reduces civil installation time

  • Off-site build – The unique, above ground, modules are manufactured, engineered and wet tested in a quality controlled environment, reducing on-site installation time and health and safety risk.
  • Ease of access – The modular design of the tanks are designed for ease of transportation and accommodates unusual height or width restrictive access.
  • Ease of off-loading – The units can an be delivered and off-loaded by a lorry crane (Hiab), removing the need for large lifting equipment on-site during installation.
  • Control kiosks – Blowers and panels equipment are also pre-built to reduce on-site installation, with the additional option of telemetry.


Engineering design

  • Process – Designed to meet on site specification and high treatment standards for biochemical oxygen demand (BOD), ammonium (NH4) and soluble chemical oxygen demand (COD).  Additional equipment can be added to remove phosphorus (P). The process can also be configured to provide anoxic conditions for nitrate (NO3) removal.
  • Process – The modular design can be combined with both upstream and downstream treatment equipment based on individual process requirements.
  • Running costs – Option of allowing blowers to be driven by variable speed drives (VSD’s), controlled by dissolved oxygen (DO) and/or ammonia monitors. This delivers further reductions in energy consumption; reducing overall carbon footprint and running costs.
  • BIM – Modular construction and configuration can meet site-specific requirements incorporating BIM workflow principle.
  • Compliant –  All WPL SAF units meet WIMES, specific water utility asset standards, CDM regulations, European norms and directives.



  • No need for high level access for internal maintenance which significantly reduces health and safety risk.
  • No need to drain the tanks or remove the media, minimising maintenance.
  •  No internal moving parts or maintenance required within the tank.
  • GRP and galvanised steel or stainless steel frame reduces maintenance costs, no need for repainting of steel structure.


Continued research and development

  • The internal configuration of the WPL SAF process technology, along with the modular structure of the hybrid tank design have fused together to significantly improve efficiency and reduce carbon footprint.
  • The WPL SAF process technology is patent pending.



  • Manufactured, engineered and wet tested in WPL’s quality controlled factory environment, reducing on-site installation time which further reduces health and safety risk.
  • Modular units are a combination of UV stabilised GRP external gel coat finish and galvanised steel or stainless steel structural ‘exoskeleton’ – design life of 25 years.
  • Standard UK unit size is 2.8m (L) x 2.8m (W) x 3.1m (H).
  • Containerised modular export units are available on request.


For specification information please download the WPL Hybrid-SAF data sheet – brochure option.

WPL SAF options

Our WPL SAF’s can also be manufactured in:

WPL SAF hire options are also available in steel and GRP

Case study: at a glance

Modular installation at a Sandbach & Lawton Gate WwTW – United Utilities

Some 12 x WPL Hybrid-SAF modules have been installed in four treatment streams at Sandbach wastewater treatment works (WwTW).

Meanwhile, six WPL Hybrid-SAF modules are now providing two additional treatment streams at Lawton Gate WwTW.

Arrival of Modular Hybrid SAF at Sandbach site

Installation and commissioning  in 5 days

Offloaded over two days and was set up and commissioned within five days.

The plants are likely to be needed at these sites for approximately five years. However, they can be transported from site-to-site as required in the future.

Image of Modular Hybrid SAF (submerged aeated filtration) for BOD and ammonia removal being installed at Sandbach


Neil Wilkinson, Projects Manager, Nomenca said:

“The modular nature of WPL’s Hybrid-SAF gives the wastewater treatment plant managers at Sandbach and Lawton Gate flexibility in terms of operation along with the additional capacity required. They can work alongside existing process systems, so they were a good choice at these sites.

“Working in close partnership with WPL, each process plant was delivered on time and within budget.”


Technical director, Andrew Baird, returns to Sandbach WwTw site, post installation, to measure the performance through the dissolved oxygen levels of the WPL Hybrid SAF (submerged aerated filter).

Image of WPL Technical Director, Andrew Baird at Sandbach site

Read full case study Modular treatment plant delivers flexible upgrade for United Utilites