Flexible 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, minimising the risk of compliance failures. Product flexibility makes the plant suitable for a vast range of applications, from sewage to industrial trade wastewater treatment.

The WPL Hybrid-SAF is designed to meet on site specification and high treatment standards for biochemical oxygen demand (BOD), ammonium (NH4), nitrate (NO3) 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.

Scalable to accommodate large wastewater treatment works, the modular units are simple to transport, install and operate, requiring minimal maintenance.

The modular nature of the WPL Hybrid-SAF means units can be installed even where sites face height and width constraints. In certain circumstances, WPL can increase the height or width of individual units at the design stage to accommodate site constraints.

The units are manufactured, engineered and tested off-site in a quality controlled environment, reducing on-site installation time and health and safety risk.


Why you should choose the WPL Hybrid-SAF:

Flexible modular design

  • Designed to fit sites with a small or unusual footprint
  • Scalable to accommodate a growing population of up to 10,000 population equivalent (PE)
  • Transportable asset during site modification
  • Can redeploy elsewhere if an existing installation becomes redundant before the end of its life.
  • Modular units can operate as an individual treatment plant or be designed to be connected in series to form a larger plant

Reduces civil installation time

  • Off-site tank manufacture reduces on-site installation time and health and safety risk
  • Modularity allows ease of transportation and accommodates unusual height or width restrictive access
  • Can be delivered and off-loaded by a lorry crane (Hiab), removing the need for large lifting equipment
  • Control kiosks with blowers, panels and optional telemetry equipment are also pre-built to reduce on-site installation

Engineering design

  • Can be combined with both upstream and downstream treatment equipment
  • 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 footprints and running costs

Reduced maintenance

  • No need for high level access for internal maintenance
  • No need to drain the tanks or remove the media
  • No internal moving parts or maintenance required within the tank


  • Meets stringent environmental discharge standards
  • Fully compliant WIMES specification, British Standards and other European Norms
  • Designed to meet individual UK water utility specifications
  • Designed to BS12255 – parts 1 to 15

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
  • Modular units are a combination of UV stabilised GRP with an external gel coat finish and galvanised steel or stainless steel structural ‘exoskeleton’ – design life of 25 years
  • Standard unit size (UK) is 2820mm (l) x 2820mm (w) x 3300mm (h)

Technical specification

For technical specification information (including indicative drawing), please download  the WPL Hybrid-SAF datasheet (available on this page).

Case study: at a glance

Image of WPL Technical Director, Andrew Baird at Sandbach site

United Utilities (UU) Wastewater Treatment Works – Sandbach in Cheshire and Lawton Gate in Staffordshire.

Each of the two site installations was delivered and offloaded over two days and was set up and commissioned within five days.

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