WPL HiPAF Modular

Please click here to download the HiPAF Wastewater Treatment Brochure

Sewage treatment HiPAF-Modular-+-Kiosk-Loch-Lomand.jpgHiPAF-LogoHiPAF Modular sewage treatment plant for
250-3,000 people

The WPL HiPAF range offers bespoke SAF (submerged aerated filter) sewage treatment plant solutions specifically designed to meet demanding, individual site requirements. 

Why HiPAF?

HiPAF combines versatility, efficient processing, reliability and robust design, meeting all Environment Agency standards while minimising visual impact on the landscape.

Sewage treatment for service station HiPAF-with-Kiosk---McDonalds.jpgWith more than 1,400 units installed throughout the UK and overseas, the HiPAF is regularly specified by Water Utility first time sewerage schemes and upgrades to rural works, including United Utilities, Yorkshire Water, Anglian Water and Southern Water.  It is also the preferred choice in many commercial and domestic applications that are not connected to mains drainage.

The HiPAF Modular sewage treatment plant comprises separate primary settlement, biological treatment and final settlement modules that are used to construct very large treatment works, in GRP (Glass Reinforced Plastic), installed below ground.

It provides treatment for Biological Oxygen Demand (BOD), Suspended Solids (SS) and ammonia (NH4) in wastewater applications for populations ranging from 250-3000 people.  With an optional ‘add-on’ sand filter, it will attain a treatment quality of BOD 10mg/l: SS 10mg/l: Ammonia  2mg/l.


  • Copes with variable flows and loads with unique flow balancing in primary tank
  • Reliable operation and stand-by facility
  • Low maintenance required as the HiPAF has no internal mechanical moving parts
  • Safe, clean, accessible air diffuser system with large access lids for easy maintenance
  • No emptying of tank required during maintenance of air distribution system
  • Humus and primary sludge are stored in one place for simple tankering operation
  • Small installation footprint, low installation costs, minimal visual impact

Only from WPL

The HiPAF package includes:

  • Complete in-house design and specification service
  • Turnkey service via our preferred contractor network, which includes initial site survey, commissioning and project liaison, if required, as optional extras

HiPAF treatment process

Primary Settlement

Primary settlement is in accordance with BS6297, giving the required hydraulic retention time and ensuring that 30% of the BOD will settle out in the primary tank.  HiPAF plants below 500 persons will have sludge storage integral to the primary tank. Above 500 persons it may become more cost effective to provide separate sludge storage and / or digestion.

The primary settlement tank is equipped with baffles to prevent floating scum entering the biological phase of the treatment process.  It also incorporates WPL’s unique forward feed system which lowers the level in the tank, during periods of low flow, to provide a buffering capacity for possible surges in the influent. The forward feed also mitigates process risks associated with variable loads.

Biological Treatment

After primary settlement, the settled liquor flows to the biological treatment unit by displacement and via the air lift forward feed.  The biozone is fully segmented internally to eliminate the risk of process short cuts and to provide an efficient nitrifying environment.  Each biozone segment is filled with high voidage plastic filter media, where both carbonaceous and nitrifying processes take place. Air to oxygenate the influent and to scour excess biomass from the filter media is introduced continuously below each chamber by a series of diffusers.

Final Settlement

Following biological treatment the effluent flows into the final (humus) settlement tank where the excess biomass settles out.  The humus tank is equipped with air lifts which are arranged to automatically transfer settled humus sludge to the primary tank for co-settlement.  The treated effluent flows under gravity to the works outfall.

Sewage Treatment HiPAF Midi 3D without labels

Cut-away graphic showing the treatment process

1. Primary settlement tank
5. Air diffusers at the bottom of each chamber
2. Settled solids at bottom
6. Filter media
3. Unique air lift forward feed into
7. Settled sludge air lift back to primary
8. Final (humus) settlement tank
4. Biological treatment unit (biozone)

Control kiosk

Each HiPAF comes complete with a discreet, weatherproof, acoustically lined GRP kiosk, situated above ground. This houses the blower(s), a Form 2 control panel and air distribution manifold.
Included as standard is 10m of airline, to connect the blowers to the tank. Blower and airline upgrades are available if the kiosk is sited further than 10m from the plant.
The Form 2 control panel automatically controls the operation of the plant (Form 4 is also available).
Please contact us or talk to your authorised distributor for advice.

Internal Configuration

Wastewater treatment for Water Utilities HiPAF-lids-up-showing-Biozone.jpgThe internal sections of the plant are accessible from the top by opening the access lids, for easy servicing, maintenance and de-sludging. The plant is fitted, as standard, with large, stainless steel, gas strut assisted lids. to give full access to these parts of the plant. Other lid types are available.
Air is introduced to the HiPAF unit by a series of air diffusers. Each air diffuser is capable of being isolated and removed individually without the need to shut down the plant or affect air supply to the rest of the unit.

The complete absence of mechanical and electrical components within the hostile environment provides safe and clean working conditions on site.

Additional extras and upgrades

  • Water Utilities sewage treatment HiPAF-Mark-3-lids.jpgLid type, orientation and colour finish options are available
  • Tertiary treatment options for more stringed consent standards
  • Inverts up to 1.5m with turret extensions
  • Separate Robust Aerobic Digestion System (RADS) sludge handling and sludge digestion
  • Volt-free telemetry contacts on control panel
  • Form 4 control panel
  • Pumped inlet flow control chamber
  • Permanent or temporary solutions
  • Blower and airline hose upgrades
  • GRP or steel construction for transportable plants and above ground installations

WPL HiPAF is the ideal sewage treatment solution for:

  • Water Utility first time sewerage schemes
    and upgrades to rural works
  • Camping and caravanning sites
  • Villages, rural communities and housing associations
  • Motorway service stations
  • Hotels and leisure centres

  • Zoos/theme parks/leisure attractions
  • Schools
  • MOD and custodial establishments
  • Rural industrial buildings and offices
  • International projects

Waste water treatment for motorway service station HiPAF-Modular-+-Conical-tanks.jpg Wastewater treatment HiPAF-Modular-M40-Beaconsfield.jpg Waste water treatment HiPAF-Modular-Plant---separate-tanks.jpg

Dimensions and technical specifications

For further product information and technical specification please download the WPL HiPAF brochure

Here to Help

We hope you can find everything you need here on our website but if you have any questions, please don't hesitate to call us on 023 92242 600 or email enquiries@wpl.co.uk we'll be happy to help.

Registered Company Address: Units 1 & 2 Aston Road, Waterlooville, Hampshire, PO7 7UX, UK | Tel: 023 92242 600
Company Registration Number: 02583411