WPL HiPAF Modular

Wastewater treatment system (up to 2,000 people equivalent)


The WPL HiPAF  modular sewage or industrial effluent treatment plant offers packaged wastewater treatment solutions for properties of up to 2,000 population equivalent (PE) where mains drainage is unavailable. The HiPAF modular design for sewage treatment consists of a separate primary settlement, a HiPAF SAF (submerged aerated filter) for biological treatment and final settlement modules.

WPL’s modular wastewater treatment plants are designed to meet site specific requirements, our plants can be configured to meet various population sizes and to meet demanding, individual site requirements.

The WPL HiPAF modular package offers a complete in-house design and specification service including a turnkey service of initial site survey, commissioning and project liaison if required.

Suitable for larger applications and manufactured from glass reinforced plastic (GRP), the modular sewage treatment plant is installed below ground.


Features and benefits of the HiPAF modular wastewater treatment plant:

Low running cost and maintenance

  • The HiPAF modular design has no internal mechanical moving parts therefore the sewage plant requires minimal annual maintenance
  • Emptying of the tank is also not required during maintenance of air distribution system

Low installation costs and flexibility on site

  • Only a small excavation is required due to its compact HiPAF modular design allowing flexibility of positioning on site

Bespoke configurations

  • Energy saving options and chemical dosing packages can be configured to the design for site specific requirements

Minimal visual impact

  • The HiPAF modular does not impede views due to the below ground installation

Variable flows and loads

  • The unique design of the flow balancing in the primary tank means it can cope with variable flows and loads


  • Robust operation and stand-by facility

Easy access

  • Safe, clean, accessible air diffuser system with large access lids for easy maintenance

Simple tankering operation

  • Humus and primary sludge are stored in one place for simple tankering operation

Tank 25 years life

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

WPL tailor our robust and reliable HiPAF modular solutions to meet our clients’ demanding specifications and expectations.

Typical commercial uses of the HiPAF modular sewage treatment plant include:

  • Animal waste options such as stables and kennels
  • Agricultural growers and garden centres
  • Camping and caravanning sites
  • Custodial establishments
  • Golf courses and fishing lodges
  • Hotels, restaurants and public houses
  • Housing developments
  • Motorway service stations
  • Manufacturing – industrial trade effluent
  • Care homes and retirement villages
  • Commercial buildings and offices
  • Schools, colleges and training centres
  • Stately homes and large country estates
  • Villages and rural communities
  • Visitor centres
  • Zoos, theme parks and leisure attractions and leisure centres

For water utilities requirement, please see WPL HiPAF® Bespoke System

 The WPL HiPAF Modular Standard

The WPL HiPAF modular sewage treatment range meets the following industry standards:

  • Fully compliant with UK Building Regulations and Environment Agency (EA) guidelines
  • The WPL HiPAF is designed using the British Water Code of Practice Flows and Loads, to ensure correct sized tanks
  • Designed to BS EN 12255 – 1/15 and manufactured using BS 4994

The HiPAF modular sewage treatment plant can be configured with additional options to meet site specific requirements:

  • WPL’s balancing tanks should be considered when sites have variable occupancy levels, such as sporting and wedding facilities
  • Installing WPL RADS can reduce de-sludge frequencies on the biological treatment plant by 75% offering extended de-sludge intervals
  • WPL Sand Filters can improve final effluent for strict consent requirements
  • WPL can supply a duty/standby blowers with automatic change over to ensure an uninterrupted air supply  and maintain high levels of treatment
  • Energy saving options such as variable speed drive blowers are available


The WPL HiPAF™ brand (High Performance Aerated Filter) references the unique hydrodynamic profile within the filter bed.  The benefit of the aerated filter 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 guarantee to suit both 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.

Standard kiosk design for commercial applications

Each HiPAF modular sewage treatment plant 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.

Kiosks upgrades are available on request e.g. walk in kiosk.

Example of a standard (large) kiosk
Image of WPL standard kiosk, a component of a WPL sewage and wastewater treatment system

MK2 lids for commercial application:

  • All lids are lockable
  • Large lids for easy access to each zone
  • Assisted lifting with gas struts
  • Fully serviceable due to easy access
  • Easily removable air diffusers
  • Optional safety grating when in place prevents risk of fall

WPL HiPAF sewage treatment plant showing gas strut open lids  Image showing the internal configuration of a WPL HiPAF sewage treatment plant

The HiPAF Treatment Process

  • Primary – Primary settlement is in accordance with EN12255-4, giving the required hydraulic retention time and ensuring that 30% of the BOD will settle out in the primary tank.  WPL’s HiPAF plants below 500 persons will have sludge storage integral to the primary tank. The primary settlement tank is equipped with baffles to prevent floating scum entering the biological phase of the sewage 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.
  • Biological – After the primary settlement stage, 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. Each biozone segment is filled with high voidage plastic filter media, where both carbonaceous and nitrifying processes take place, mitigating process risks associated with variable loads. 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 – Following the biological treatment stage 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.

HiPAF solution | Municipality Zgornja Kungota, Slovenia