Nitrifying-SAF Ammonia


Ammonia removal using WPL Nitrifying-SAF wastewater treatment plant uses a tried and proven technology for applications where the Biochemical Oxygen Demand (BOD) has been completely removed (below 20 mg/l average), but effluent is required to be fully nitrified, and further biological capacity is required for this application.


Features and benefits of the nitrifying SAF ammonia treatment plant:

Proven consistent process reliability

  • Sub 1mg/l ammonia and 10mg/l BOD
  • Variable speed of operation improves process performance

Low operating costs

  • Self-scouring, no need to de-sludge units

Low maintenance

  • No internal moving parts and safe working access for maintenance
  • Retention time’s air flow rates and blower control play a major factor in the design

Simple and easy configuration

  • When on-site with existing processes solution

Quick turnaround

  • From receipt of order to providing an on-site solution


  • Final engineering solution takes in to consideration ease of transportation to difficult access sites


  • Easy to move off site at a later date if the process is no longer required or relocate to another site

 Can tailor air use

  • Optimise energy consumption depending on site requirement

WPL tailor our robust and reliable nitrifying SAF ammonia treatment plant solutions to meet our clients’ demanding specifications and expectations.

Above ground installation, manufacturing options include:

  • Modular WPL Hybrid SAF – glass reinforced plastic (GRP) with galvanised or stainless steel ‘exoskeleton’
  • Stainless steel or steel tanks

Below ground installation, manufacturing options include:

  • HiPAF range – glass reinforced plastic (GRP)

All GRP used in WPL sewage treatment products are UV stabilised external gel coat finish which extends the asset life to 25 years

WPL’s nitrifying SAF ammonia treatment plants are manufactured with full access to all parts of the unit, all mechanical and electrical equipment is located in a separate, dedicated enclosure for easy maintenance.

The SAF sewage treatment units are suitable for permanent or temporary applications, with a number of different hire and purchase options to suit requirements. They can be used either to undertake full biological treatment or to complement existing wastewater treatment process units.

WPL delivers bespoke wastewater process solutions which take into consideration investment and cost recovery, when tailoring the product offering to meet the varying specifications individual clients demand.

Stringent Consent Standards

As with all WPL SAF’s the WPL Nitrifying-SAF  Ammonia Treatment meets even the most stringent consent standards imposed due to a combination of fixed film, fluidised bed and suspended biomass reactions whist supporting customer needs such as:

  • Existing sewage treatment works which the regulator (SEPA / EA) have tightened or lowered the ammonia quality specified for the effluent discharge.
  • Existing sewage treatment works which is at risk of breaching the consent to discharge for ammonia.
  • Proactive or reactive refurbishment work needs to take place whereby existing assets are taken off-line and the client has proactively determined this work will potentially put the discharge consent at risk.

Transportable units | Huyton wastewater treatment works


  • Five WPL ST1000 Model units were required for this project, the modular nature of the equipment means it can be readily redeployed to other sites and configured in any combination – as five units or just one.
  • The units needed to meet a demand of 5Ml/day so that the nitrifying tertiary filter could be taken off line.
  • Read full case study | Transportable units keep treatment moving for United Utilities

 High Performance Results | Danesmoor wastewater treatment works


  • Challenging access | eight steel modular SAF units were transported avoiding overhead electric cables and fit down narrow country lanes.
  • The tanks when on-site were lifted, rotated and placed on a prepared concrete slab.
  • Factory ‘kit,’ build | manufactured and engineered off-site meant that less workers were required at Yorkshire Water’s site, in turn minimising the risk of health and safety and quality control.
  • High performance results | infographic 

 WPL HiPAF Options:

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.

The WPL HiPAF Range is manufactured from glass reinforced plastic (GRP) and the range includes:

  • The WPL HiPAF modular (up to 2000 population) is a WPL standard primary tank, separate SAF and humus settlement tank.  The modular design can be configured with additional options depending on site requirements.  Installed below ground
  • WPL HiPAF bespoke (up to 5000 + population) sewage systems could use an existing primary tank on site, WPLs SAF and combine with a WPL’s humus settlement tank, lamella or conical tank depending on customer or site requirement.  Installed below ground.

 The company’s SAF processes:

  • Submerged aerated filter (fixed film SAF) – versatile modular sewage systems that can be used to undertake full biological treatment or to complement existing process units in aerated fixed-film, anoxic fixed-film or aerated fluidised bed design options
  • AN-SAF (Total N treatment) – has been developed for applications that require Total N treatment. Pre and post anoxic treatment is possible, in combination with the standard aerated process
  • Nitrifying-SAF Ammonia Treatment – technology for applications where the Biochemical Oxygen Demand (BOD) has been completely removed (below 20 mg/l average), but effluent is required to be fully nitrified, and further biological capacity is required for this application