WPL HiPAF Eco Midi (up to 150 PE)

The WPL HiPAF Eco Midi sewage treatment plant for off mains drainage is designed to reduce whole life costs without compromising the robust process performance.

Design Build

Specification options are available for the WPL HiPF Eco Midi to design build your own sewage treatment plant based on preferred maintenance or a demanding, individual site requirement.

The low maintenance, economical WPL HiPAF Eco Midi models are built for light pedestrian usage.  Heavy duty applications can be achieved subject to a structural engineer’s advice.  The access is via turrets with light duty lids for ease of de-sludging.


  • Fully compliant with UK Building Regulations and Environment Agency (EA) guidelines.
  • Economy models are designed to exceed Royal Commission Standards.
  • Tighter standards can be achieved, making the WPL HiPAF sewage treatment plant the preferred choice for sensitive locations such as a Site of Special Scientific Interest (SSSI) ensuring Environmental Agency (EA) consent to discharge standards are met.
  • CE marked, designed to BS EN 12255 – 1/15 and is fully compliant with UK Building Regulations.
  • WPL use the British Water Code of Practice Flows and Loads, to ensure plants are correctly sized.

 Why you should choose the WPL HiPAF Eco Midi:

Small footprint and ease of installation

      • One of the smallest wastewater treatment units on the market – through extensive research and development, WPL use high surface area random plastic media offering optimum improved performance, minimising footprint and power consumption.
      • The rectangular tank shape utilises the full base area of the treatment zone for aeration arrays ensuring total circulation, without “dead zones,” offering a highly efficient treatment.
      • Flexible inverts with a depth up to 1.5m to accommodate deeper drainage which significantly reduces the need for an external pump chamber.
      • Low dry weight design allows for off-loading with a truck mounted hiab.
      • Integral lifting eyes for improved on-site handling.
      • ‘Keying-in’ lip to assist anchoring into concrete surround.
      • High specification weatherproof kiosk made in GRP situated above ground to house the control panel.

Energy efficient

      • Eco kiosk with independent blowers as standard to significantly reduce power consumption.
      • Designed to use minimum possible power requirements in a submerged aerated filter (SAF) unit.
      • Duty standby blower arrangement is available.

Low maintenance

      • No internal mechanical or electrical moving parts, therefore requiring minimal annual maintenance.
      • Low energy compressors, with adjustable timers, ensure minimal running, maintenance and servicing costs.
      • Simple tankering operation as the primary sludge and sludge generated from final clarification are stored in one place for ease of removal.

Variable flows and loads

      • During low flow conditions the level in the primary tank is reduced utilising forward feed air lift pumps. This creates a buffering volume that reduces the impact during high flows.
      • WPL can design the plant to continue to operate well during seasonal variations reducing total power consumption.

Robust process

      • Proven WPL SAF technology is based on over 25 years empirical data. The reliability is underpinned by the selection of high quality blowers and pumps.
      • Internal recirculation leads to increased process performance.

Minimal visual impact

      • Below ground installation has minimal environmental impact as it does not impede views.

Tank 25 years life

      • GRP is UV stabilised with an external gel coat finish which extends the asset life to 25 years.
      • WPL HiPAF plants and kiosks are produced in a quality controlled environment at the WPL factory.

Optional Extras

      • Inverts: 0.45m as standard and can go up to 2m.
      • External pump chamber.
      • Pumped flow controller.
      • Kiosks: medium.
      • Energy saving duty stand by blowers.


Typical applications for the WPL HiPAF Eco Midi sewage treatment plant:

      • Agricultural growers and garden centres
      • Camping and caravanning sites
      • Golf courses and fishing lodges
      • Hotels, restaurants and public houses
      • Care homes and retirement villages
      • Commercial buildings and offices
      • Housing Developments
      • Schools, colleges and training centres
      • Stately homes and large country estates
      • Villages and rural communities
      • Visitor centre

 Indicative Technical drawing of the WPL HiPAF Eco Midi

              Image of technical specifications table for WPL Eco HiPAF Midi

 Technical Information

Image of technical specifications table for WPL Eco HiPAF Midi

Design Parameters


Process Options

      • WPL RADS (sludge storage and reduction) significantly extend de-sludge intervals by 75%, reducing tankering costs.
      • WPL Balancing Tanks, when sites have variable occupancy levels, such as sporting and wedding facilities, ensuring a consistent flow to the plant.
      • WPL Sand Filters can improve final effluent for strict consent requirement.

The WPL HiPAF™ brand (High Performance Aerated Filter) references the unique hydrodynamic profile within the filter bed.  The benefit is a stable even biomass growth, during high or low flows meaning WPL is offering higher treatment efficiencies over other similar solutions on the market.

WPL’s robust biological treatment process guarantees to suit BOD and Ammonia removal and is underpinned by 25 years of empirical data offering treatment for carbonaceous ﴾BOD﴿ removal, nitrification and de‐nitrification ﴾Total N﴿ when strict standards are required.