TechnologyAbout The Aero-Fac® Wastewater Systems

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Aero-Fac® Wastewater Treatment System

A Greener “Nature Based Solution”


page aero errolAero-Fac® is a low carbon footprint biological wastewater treatment system that has been well proven for over two decades in the UK in a variety of municipal and industrial wastewater applications in all types of climates. Aero-Fac® employs a highly advanced and optimised version of a completely biological aerated facultative treatment process, a truly green “Nature Based Solution”, that automatically adjusts to handle extreme variations in flow and load. Aero-Fac® incorporates remarkably fast and easy construction techniques, utilises renewable energy, requires exceptionally easy operator skills and almost no  operator intervention or maintenance, and yet produces excellent naturally disinfected effluent quality that can be superior for discharge, reuse and/or irrigation.


page aero profile new small Aero-Fac® offers a number of unique “green” benefits, not the least of which is a self-digesting sludge process that requires no pre-screening, sedimentation tanks, clarifiers, sludge removal, dewatering, chemicals or conditioning, and best of all, Aero-Fac® requires no routine sludge disposal or the associated lorry tanker traffic in and out of the treatment plant. Sludge is continuously biochemically self-digested within the initial treatment stage eliminating costly equipment, labour and ever-tightening regulation.


Water industry personnel are routinely amazed by the lack of odour at Aero-Fac® WwTPs. Many remark that it is hard to believe that they are actually at a sewage treatment plant! For years Gurney Environmental has had an enviable reputation for its ability to solve severe odour problems associated with existing treatment plants.


Another advantage of Aero-Fac® is the very low operating cost. Gurney Environmental is unique in its use of a fully biological process along with wind powered aerator/mixers (renewable energy) matched with an innovative diffused air aeration system. Overall the system can operate at anywhere from 40-85% less than typical activated sludge systems – truly sustainable.

The wind powered SERIES 3 units have been extensively proven in wastewater treatment and other applications. The completely stainless steel diffused air aeration components are also unique in that they require no routine cleaning or maintenance resulting in an extremely low total life-cycle cost.



Seldom does a wastewater treatment plant see exactly the same flows or loadings throughout its lifetime or even during various parts of a day, week, month or year. Whether from tourism, storm water infiltration and flows (CSOs), local industry, growth or other issues, flows and loads vary at many facilities. This is where Aero-Fac® really shines with the ability to automatically adjust.



By employing a much more biological underlying process — the facultative biological process — significant costs can be eliminated in both the initial capital costs (CAPEX) of construction and equipment and the ongoing 20-year operating costs (OPEX). Facultative processing – a free gift of nature – can stabilise wastewater more thoroughly than standard mechanical treatment, and do it for a fraction of the cost and complexity.

Advanced methods developed and used by Gurney Environmental in the Aero-Fac® system enhances the natural facultative biological process's ability to fully stabilise wastewater while simultaneously self-digesting all incoming sludge, all without odour.

Using a pure biochemical, natural process with supplemental process enhancing technologies provides 1) a massive aerobic processing section, 2) a specialised facultative bacterial zone, 3) plus a full anaerobic sludge digestion section for total 100% on-site treatment. Additionally, special attached biofilm technology is available from Gurney Environmental for further polishing of effluent. This fundamental difference creates a major difference in initial costs and ongoing 20-year operating and maintenance costs.


BOD and other reductions within a facultative biological process are a function of retention time and average water temp­erature. Assuming that the critical 3 layers of biology are established, and the upper aerobic and the sludge/water interface facultative layers have oxygen available, BOD and other reductions will occur as part of the natural, reliable and predictable biochemical process. If a treatment system can maintain a residual DO, the biology will process at a maximum rate for a given temperature over a given time.

In other words, by the laws of nature, BOD and other reductions will occur if DO is present and the layering is undisturbed. Increasing the retention time increases the removal rate, with retention time based on average seasonal water temperatures. Systems have operated reliably for decades in less than 0ºC winter climates. Aero-Fac® is uniquely designed to provide the absolute optimum conditions for predictable removal rates, all whilst dramatically lowering operating costs and total carbon footprint.

Improved Effluent Results at Converted WwTP


Modular Design of Aero-Fac® Allows Easy Scaling From Smaller up to Peri-Urban WwTPs

Aero-Fac® systems are generally configured with both primary and secondary stages of treatment (a third stage is optional when needed). Each “train” or “module” of parallel cells can provide 100% on-site treatment including enhanced disinfection and full nitrification. Modules are designed with correct length-to-width ratios for proper flow and uniform loading, and built to a maximum size for controlled, predictable performance.

As flows increase, additional trains or modules are added, thereby providing a true scalability. The use of a modular design also allows for the ability to use a distributed or multi-location design scheme for larger applications including peri-urban scenarios.




Combined sewer systems collect rainwater runoff, domestic sewage and industrial wastewater in the same pipe. Most of the time, combined sewer systems transport wastewater to a sewage treatment plant where it is treated and then safely discharged to a water body — if flows stay within the daily capacity of the WwTP! However, during periods of heavy rainfall or snowmelt, the wastewater volume in a combined sewer system can exceed the capacity of the treatment plant. For this reason, combined sewer systems are designed to occasionally overflow and discharge excess wastewater directly to nearby streams, rivers, or other water bodies. These overflows, called combined sewer overflows (CSOs), contain not only storm water but also untreated human and industrial waste, toxic materials, and debris.

Aero-Fac® is uniquely designed to handle peak flow and loads automatically without operator intervention, and do so utilising both renewable energy (wind power) and low energy diffused air aeration. Whether peaks are from tourism, storm events, industrial flow variations or population growth, Aero-Fac® uniquely automatically handles the changes without excess costs or intervention.

By design both the primary and secondary treatment cells in an Aero-Fac® system are designed for 20-25 days of retention, thereby buffering any typical 3 or 6x storm surge or other peak flow/load event. The windpowered aeration units provide the necessary aeration and optimised biological conditions for full treatment, but if the actual loading also increases going beyond the renewable energy’s aeration capacity, the low energy diffused aeration kicks in momentarily to cost-effectively handle those peaks.

The “secret” to Aero-Fac’s® capability to handle dramatic flow/load variations is the essential design. Uniquely, Aero-Fac® can operate with virtually no load for extended periods whilst also having the ability to suddenly/instantly handle much larger flow/loads. Aero-Fac® cells are designed to handle the maximum average flow/load over a 20-25 day period, but can automatically without operator intervention revert to low-to-zero flow/loads without any loss of performance.

The Aero-Fac® facultative biological process has decades of well-proven performance and is considerably more stable and robust under varying flow/load conditions, thereby affording more flexible and stable performance over the years. A truly sustainable, lower carbon footprint option!


Aero-Fac®, a truly “Nature Based Solution”, offers impressive and significantly greener advantages over other wastewater treatment systems that can result in less labour, less ongoing cost and more reliable operations and superior effluent quality. Overall, Aero-Fac® offers an extremely low total life cost and true long-term sustainability as compared to other systems.



The extraordinarily low carbon footprint Aero-Fac® wastewater treatment system is becoming the key solution to eliminating CSOs, odour, sludge handling, while reducing the carbon footprint and embodied carbon, and dramatically cutting both OPEX & CAPEX costs by employing a well-proven Nature Based Solution.

Yorkshire Water’s Aero-Fac® WwTP Finalist for a Third 2023 Global Sustainability Award

Gurney Environmental, Yorkshire Water, Stantec and Ward & Burke (the construction company) were announced as finalists in the 2023 British Construction Industry (BCI) Awards for Environment & Sustainability Initiative of the Year for the Aero-Fac® WwTP project at Withernsea/Hollym, Myers Lane. Judges are selected from major clients, government and industry recognised figures, and contribute valuable time and effort to work through hundreds of entries, reviewing against strict criteria and attributing scores aimed at rewarding and recognising the very best in project excellence. The British Construction Industry Awards has the most prestigious and rigorous judging process and now in its 36th year, the awards have built up an outstanding reputation for recognising only the very best projects and companies in the industry.

ICE Medal Gives Global Recognition in 2023 for Aero-Fac® Sustainability

Earlier this year, the 2023 ICE Edmund Hambly Medal for “Design for Sustainable Development” was awarded to Yorkshire Water’s new 15,000 PE Aero-Fac® WwTP at Withernsea (Hollym, Myers Lane). The international award underscores the unusual sustainability along with OPEX and CAPEX cost savings of the project as compared to past traditional options — plus the ability to operate with little ongoing manpower, energy, maintenance — and all with a substantially lower carbon footprint.

The ICE Edmund Hambly Medal – Creative Design for Sustainable Development
The Edmund Hambly Medal aligns with ICE’s commitment to address how we build resilience and mitigate the significant effects of the climate change. It is an award for the creative design of an engineering project that makes a substantial contribution to sustainable development. The award emphasises the important contribution that civil engineering makes to the wellbeing of mankind and the environment. This year the award will seek to recognise the creative design of an engineering project that contributed to mitigating and adapting to the significant effects of the climate change.

Two major infrastructure projects in Hong Kong won runner-up Highly Commended recognition for this same ICE Award.

Aero-Fac® 2023 Finalist for Water Industry Awards

In another recognition, earlier this year, Stantec and Yorkshire Water were finalists for an award at this year’s Water Industry Awards for the Net Zero Carbon Initiative for their work as partners with Gurney Environmental in the design and construction of the innovative Aero-Fac® WwTP at Withernsea.




The TYTAN® Titanium Algae Management System is a broadband frequency device designed to transmit ultrasound directly through the water, with an exposed titanium face that cleans itself during operation. This design means that maintenance is minimal, which is important in situations where contact with water is hazardous such as sewage treatment cells. The TYTAN® system covers all frequencies to address a range of algal species and does so without requiring repro­gramm­ing for different algal species as some other systems do.

The TYTAN® has a wide range of applications from open waters, irrigation lakes, canals, reservoirs, drinking water systems, sewage treatment lagoons, wetland polishing systems, natural swimming pools, biofilm control and antifouling of boat hulls in marinas.

Industrial Quality

The system is truly designed and manufactured to “industrial quality” standards for tough industrial applications, and is manufactured of titanium and stainless steel. Each unit covers a maximum line-of-sight area of about 21 hectares.





THE NITRO-FAC® SYSTEM is a green, innovative biological ammonia-nitrogen reduction system using a fixed film media with unique and simplified components for use in polishing effluent.

Using well proven fixed film media technology, this biological process forms a nitrifying bacteria biofilm on the media and offers a low-energy, low-maintenance, positive process control solution for those applications that have restrictive ammonia-nitrogen limits for effluent quality.

Many aspects of Nitro-Fac® are unique and contribute to a simplified, low-energy, low maintenance system. The aeration source for the required high DO levels is shore-mounted. Since the system is typically on the polishing end of a facility, DO levels can be near saturation much of the time if Nitro-Fac® follows an Aero-Fac® system. Thus energy can be conserved at a substantial operating cost savings. All functional components of the aeration diffusers are retrievable and serviceable from the surface, meaning no shutdowns or dewatering to access the aeration system or media.

The openness of the media allows for full flow and oxygenation throughout. This avoids the common problem of anoxic or anaerobic areas of typical media that can result in the wrong biofilm and less overall effective surface area. A completely even flow moves through the aerated media module. In Aero-Fac® installations, the circulation of the water through the media modules is augmented by zero-to-low energy windpowered aeration/mixing/pumping modules with 0.5 kW backup motors for light wind conditions. 


page aero lt case study picv2Documented Performance for the Aero-Fac® System Treating Wastewater in the UK

Read/Download the PDF of a Long-Term Case Study of Scottish Water's Errol, Scotland WwTP where Aero-Fac® performed for 20+ years with no odour, no sludge removal or handling, no CSOs, little energy, little manpower and a Total Life Cost unattainable with other conventional technologies.

 Designed and Constructed by Partners NoSWA, Gurney Environmental and Montgomery Watson Projects (now Stantec)

The Errol works was designed as two stages of treatment carried out in two separate in-series, geomembrane lined earthen basins. Total energy requirements for the approximately 2,000 population works is about 11 kW net effective power. With the excellent winds available at Errol, the operating costs often go even lower.

The Errol wastewater treatment system incorporated what at the time were a number of highly unique “green” features, not the least of which is a self-digesting sludge process that requires no pre-screening, sedimentation tanks or clarifiers, no sludge removal, dewatering or conditioning, and best of all, no routine sludge disposal and the associated lorry traffic in and out of the works. All sludge is continuously self digested within the initial treatment stage.


Aero-Fac® Offers Clear Benefits

page aero 5 Benefits 1 Stainless

100% Stainless Steel

No plastic. No rubber membranes. No hoses. No poly materials at all. 100% of the critical diffused air aeration modules and headers are stainless steel and designed to last a lifetime with virtually no maintenance

page aero 5 Benefits 2 No Maintenance

No Membrane Maintenance

The entire diffuser assembly is self-cleaning. Nor are there any membranes to clean or replace or any moving parts whatsoever. Eliminating membrane replacement alone can save thousands of pounds annually.

page aero 5 Benefits 3 Fan Blowers

Lo-Pressure Blowers

Aero-Fac® uses low-pressure fan blowers requiring virtually no maintenance, practically no routine replacement parts and an almost unlimited lifetime.

page aero 5 Benefits 4 Wind Powered

Energy-Free Aeration

Windpower provides 30-80% of the energy needed for wastewater processing. Unique wind powered SERIES 3 aerator/mixers have been proven in severe wastewater treatment applications for years, providing aeration, process acceleration and biological optimisation.

page aero 5 Benefits 5 Effluent Quality

High Quality Effluent

Water from Aero-Fac® treatment systems not only meets rigid standards, it is also better in overall quality due to advanced stabilisation of all biochemistry. This makes it ideal for water reuse options.


Clear Advantages Offered By Aero-Fac® & Accel-o-Fac®

  • icon Sludge Digestion
  • icon Shock & Peak Loads
  • icon No Odour WWTP
  • icon Modular Design
  • icon Design Assistance

No-Sludge Wastewater Treatment System

page aero sludge 1Aero-Fac® and Accel-o-fac® offer a number of unique benefits, not the least of which is a self-digesting sludge process that requires no pre-screening, sedimentation tanks, clarifiers, sludge removal, dewatering, chemicals or conditioning. And best of all, Aero-Fac® and Accel-o-fac® require no routine sludge disposal or the associated tanker traffic in and out of the treatment plant. Sludge is continuously self-digested within the initial treatment stage eliminating costly equipment, labor and regulation.

Extraordinary Flow/Load Flexibility

page aero peak flowSeldom does a wastewater treatment plant see exactly the same flows or loadings throughout its lifetime or even during various parts of a week or year. Whether from tourism, storm water infiltration/flows, industry, growth or other issues, flows and loads vary at many facilities. This is where Aero-Fac® and Accel-o-fac® really shine. Aero-Fac® and Accel-o-fac® can be designed to automatically accommodate anywhere from zero flows up to almost unlimited flows — all unattended. Shock or spike loads have little effect under most any circumstances. This makes Aero-Fac® and Accel-o-fac® ideal for tourism areas, developments with planned growth, areas with large storm water fluctuations or industrial users.

No Odour

page aero odourVirtually no odour is generated from an Aero-Fac® and Accel-o-fac® WWTP. Water industry personnel are routinely amazed by the lack of odour at Aero-Fac® and Accel-o-fac® facilities. Many remark that it is hard to believe that they are actually at a sewage treatment plant! Our technology has been used for decades to solve serious odour issues at existing facilities including both municipal and difficult industrial applications such as food processing and meat packing plants.

Scalable, Modular Design For Any Size WWTP

page aero modular Aero-Fac® and Accel-o-fac® utilise multiple cells, both in parallel trains and in series. Each cell or stage reduces BOD by about 80-85% (water temperature dependent). Parallel trains provide for a modular approach to accommodate larger flows with complete and predictable scalability. 

Examples of Modular Scaling

Design Assistance Based on Global Experience

page aero design 2Our design assistance program allows you to tap into our experience, expertise and global networking capability. Our highly experienced process engineers can be your “back room” with specific expertise when it comes to examining wastewater treatment problems or developing possible solutions, alternatives and costs. Gurney Environmental has extensive experience in process, equipment, operations and maintenance.

Aero-Fac Presentation


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100% Total On-Site Treatment

No Sludge. No Odours. Little Energy. Minimal Operating Costs.
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Decades of Research

Starting in 1976, an intensive and ongoing research program began that was designed to resolve the common problems and limitations associated with traditional wastewater lagoons/ponds including odour, short-circuiting, uneven loading, sludge accumulation and poor processing rates. 40 years later, Gurney Environmental offers technology and designs based on this 4 decades of intensive study of hundreds of municipal and industrial lagoons from around the world.

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Mechanical vs. Biological

The more biological/biochemical removal of contaminants used in a treatment scheme, the lower the initial cost (CAPEX) and ongoing costs (OPEX) for a wwtp. 40 years of research have defined the extraordinary capabilities of advanced biological/biochemical wastewater treatment.


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Truly Advanced Lagoon Design

4 decades of research based on solving problems with hundreds of wwtp's worldwide has resulted in a design philosophy that provides high rate processing, no odours and complete sludge digestion.

New-build lagoon systems are designed with the correct length-to-width ratio, parallel trains of cells to avoid large, poorly performing cells, and correct/optimal depth of cells to maintain perfect aerobic conditions while allowing for a smaller footprint. Experience does make a difference.


Comparison of OPEX in Wastewater

All Gurney Environmental systems come with design assistance and follow-on operational support.

  • Activated Sludge
  • OPEX 100%
  • High CAPEX
  • High initial cost and complex, expensive ongoing energy & operations costs
  • Shock & Peak Loads Can Upset Process
  • Prescreening Equipment Generally Required
  • Aeration Required for Both Oxygen & Mix
  • Clarifier Required
  • Can Have Odour Issues
  • Sludge Handling & Regulation Required
  • High Consumables/Chemicals
  • High Level of Operator Attention/Expertise
  • Annual Maintenance*
  • ?????
  • * 4000 m3
  • Aero-Fac®
  • OPEX –85%
  • Low CAPEX
  • Low initial cost and dramatically lower ongoing energy & operations costs
  • Easily Accepts Shock & Peak Loads
  • No Prescreening Equipment Required
  • Aeration Required only for Oxygen Demand
  • No Clarifier Required
  • Odour-Free wwtp
  • No Sludge Handling & Regulation Required
  • Few Consumables/Chemicals
  • Very Low Operator Attention/Expertise
  • Annual Maintenance*
  • £882/yr est.
  • * 4000 m3
  • Accel-o-Fac®
  • OPEX –95%
  • Lower CAPEX
  • Low initial cost and dramatically lower ongoing energy & operations costs
  • Easily Accepts Shock & Peak Loads
  • No Prescreening Equipment Required
  • Aeration Required only for Oxygen Demand
  • No Clarifier Required
  • Odour-Free wwtp
  • No Sludge Handling & Regulation Required
  • Few Consumables/Chemicals
  • Very Low Operator Attention/Expertise
  • Annual Maintenance*
  • £532/yr est.
  • * 4000 m3
  • WS Ponds
  • OPEX –97%
  • Lowest CAPEX
  • Low initial cost and low ongoing energy & operations costs, but several common problems
  • Problems With Shock & Peak Loads
  • Prescreening Equipment Sometimes Required
  • No Aeration used for Oxygen Demand
  • No Clarifier Required
  • Can Have Odour Problems
  • Possible Future Sludge Removal Required
  • Few Consumables/Chemicals
  • Very Low Operator Attention/Expertise
  • Annual Maintenance*
  • £200/yr est.
  • * 4000 m3

Both Aero-Fac® and Accel-o-Fac® can be designed as modular units and can accept a wide range of flows and loading. Both Systems can be designed as "new build" or retrofit to existing wwtp's.

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