Case Studies

TV3’s Grand Design NZ House installs an AES wastewater system on a tidal estuary

A new house build called the Black Pavillion House near Motueka, Nelson with a raised bed AES wastewater system featured on Grand Designs NZ Tues 17th October.

Grand Designs Motueka House

The property is adjacent to an inlet where tidal water rises within 5m of the northern boundary on spring tides. Combined with a high water table this requires the AES pipes to be installed in a raised bed to provide 0.6m vertical separation to the water table. Pipework suspended under the building subfloor connects to the septic tank which is also partially raised allowing effluent to gravity flow to the AES bed to achieve the required secondary treatment quality.

Grand Designs House with Raised Bed

The wastewater system design was for a four bedroom house treating 1400 l/day. The photo above shows the AES bed prior to covering with topsoil and planting with coastal shrubs. The job was designed by Gary Stevens and installed by Fusion Plumbing. The homeowners are looking forward to the ongoing low-cost performance of their AES system.

When high groundwater is a design factor, a passive AES septic system can often be achieved by mounding up the ground around the septic tank and bed, and suspending drainage pipework to conserve elevation.

Call us for more information on 03 970 7979 / 0800WASTEH2O or email us

Hillsborough Hideaway – a large AES installation featuring distribution to 4 separate pipe beds

Hillsborough Hideaway near New Plymouth is a large rural property with a range of amenities; a house, a luxury 2-bedroom rental apartment, heated pool, tennis courts, and adventure playground. In addition, a museum is being built to showcase a variety of Holden cars and memorabilia, with an adjacent restaurant.

The existing septic tank and field for the house and apartment needed to be upgraded for both the accommodation, museum and restaurant. The owner chose AES because it is an environmentally friendly and cost-effective option that could be retro-fitted to the existing system. On a sloping hillside section with a mix of soil types, the obvious site for the new septic tank, pipes and field was on the lower slopes near the road.


The wastewater system needed to be designed for a maximum daily flow of 9195 litres per day; equivalent to a per day maximum of 220 restaurant diners, 100 visitors and 11 people residing in the house & homestay.

To manage this load, the Wastewater system designer Kama Burwell of Greenbridge Design & Implementation, chose to install four separate pipe beds, level and perpendicular to the slope with each bed stepping down the gentle slope. A distribution box on the outflow from the new 25,000L septic tank sends equal amounts of flow to each pipe bed. Each bed consists of two rows of three lengths of pipe with raised connectors between each row, providing 60m of treatment pipe length in each pipe bed.


AES provides distribution boxes for this type of design and can offer technical advice for your situation if you wish to use this feature. It is ideal for wastewater treatment on large scale projects.

Preparing the cascading pipe beds
Preparing the cascading pipe beds

Pipe Bed depth dug out
Pipe Bed depth dug out

Pipes laid on sand bed
Pipes laid on sand bed

Pipe joins
Pipe joins

Filling with sand
Filling with sand

Job completed
Job completed

A Large scale Town AES installation – 200000L per day in cold temperatures

The Blodgett Landing Treatment Plant is in Newbury in the southwestern part of New Hampshire. In 2001, the town started detecting elevated nitrogen levels within the effluent and ground water. They lined the original sand filters so they could catch the effluent and pump it into a recycling tank. 50% of that effluent was recirculated to an Imhoff tank where organic material aided in reducing the nitrogen and ammonia.

However, they still had issues with attaining treatment in the winter months as well as other long term problems. The town identified the following four major issues:

  • winter operation- parts of the system would routinely freeze, hindering its operation
  • the cold weather also affected the treatment levels
  • increased de-nitrification requirements
  • a growing community required a system with increased capacity

After investigating many options, in 2010 the town choose the AdvancedEnviro-Septic® Technology for their treatment needs. As a passive wastewater treatment system tested and proven to remove up to 99% of wastewater contaminants such as BOD, TSS,TN, TKN, and Fecal Coliform it surpassed the standards required. Enviro-Septic® Systems have proven effective in cold weather. The warm effluent combined with the biological process that takes place within the pipe generates enough heat to keep the system from freezing. The Newbury Blodgett Landing Treatment Plant is designed as a re-circulating system with the patented Multi-Level™ configuration handling flows ranging from 2,500-88,000GPD.

After the wastewater is received, it goes through an initial screening and then proceeds to one of two Imhoff tanks where sedimentation and separation occurs. After the Imhoff tank, the effluent then proceeds to an equalization tank before it is dispersed to one of the four passive Enviro-Septic® treatment beds.


Each treatment bed measures approximately 90 feet long by 50 feet wide. The beds consist of 48 rows of pipe that are each 86 feet long. That means there is approximately 4,100 feet of pipe per bed or roughly 16,400 feet for the entire system. At 50,000 GPD the 16,400 feet of Enviro-Septic® pipe treats roughly 3 gallons per linear foot per day. With an impressive 25 sq ft of surface area per linear foot of EnviroSeptic®, you have over 400,000 ft2 or over 9 acres of bacterial surface area in this system. A large amount of bacterial surface combined with sufficient oxygen and other patented features allows for the high levels of treatment. These treatment beds are lined to capture the treated effluent. Once captured, the treated effluent is then pumped into a recycling tank. 75% of the treated effluent is then sent back through the Imhoff tanks via recirculation pumps and the rest is dosed into the dispersal area. As the treated effluent that is sent back to the Imhoff tanks goes anaerobic, the organic material present acts as a carbon donor in the denitrification process. Additional denitrification then takes place in the anoxic zone of the Imhoff tank.

In addition, large flow industry projects are looking for wastewater treatment options that don’t require pumps, chemicals, ongoing maintenance and alarm systems that add to staff requirements.

The following test results are averages of samples taken at the re-circulation chamber.


The town of Newbury has been very pleased with the performance and operation of this system. Plant Manager Tim Mulder said,
“Since it was installed in 2011, the system has consistently exceeded the required effluent treatment levels. The upfront cost saving of this technology along with its ability to perform with minimal ongoing cost and maintenance makes it truly exceptional in the world of large-flow wastewater treatment.”
Plant Manager, Tim Mulder