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Case Studies

TV3’s Grand Design NZ House installs an AES wastewater system near 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 in October 2017. You can view the video of the programme below.

The property is adjacent to an inlet where tidal water rises to within 5m of the northern boundary on spring tides. Combined with a high water table this required 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.

Raised Bed Installation

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 and the landscaped bed below. The job was designed by Gary Stevens and installed by Fusion Plumbing.

The AES wastewater treatment and disposal system was showcased on Grand Designs New Zealand Season 3, Episode 5 – Nelson: Black House. The wastewater installation is at 32:35 minutes.

Seasonal Worker Accommodation

An AES system was installed to cater for new-build seasonal worker accommodation for 30 people at an orchard in Richmond. Fully occupied for only part of the year, an AES system copes well with intermittent use and high demand for several months. This system was designed to cater for 200L per person per day. Kitchen facilities are also supplied to the septic tank with a grease trap to collect waste. The large, flat site with well-draining soils and a low water table made the installation of the 18.6m x 6.5m AES treatment bed straightforward. Being larger than a residential installation, the AES system was designed for effluent to gravity feed from the new 9000L septic tank to a 7 port distribution box feeding 5 subfields of AES pipe consisting of 2 rows each. Each row had 10 lengths of 3m AES pipe with a connector at the row end. The 6th port is connected to the low vent while the high vent off the end of the pipe system is supported by a nearby frame structure. The speed of effluent discharged from the septic tank is reduced by travelling through a 90-degree vertical pipe bend as it enters the distribution box into a water trap below the outlet level. A reserve of 120m2 remains undeveloped beside the bed for expansion of the soakage area if required in future. Mark Rounce of Rounce Project Solutions designed the system and Michael Marsden of Tasman Bay Plumbing did the installation.

Orchard accommodation
New accommodation block
AES treatment bed for orchard accommodation
AES pipes being laid in sand bed
seasonal worker accommodation onsite wastewater system
Distribution box delivering to 5 separate sections of AES pipes
Finished bed

DOC Campground, Lake Mahinapua, South Island West Coast

Lake Mahinapua DOC camping ground, south of Hokitika, required an upgrade of its existing wastewater system servicing a toilet block via septic tank primary treatment to low-pressure effluent dosing into a gravel filter, to cater for the addition of a new shower block.

The original system was designed 17 years ago in accordance with Auckland Council’s ‘Technical Publication #58: 1994 On-site Wastewater Systems: Design and Management Manual’ with the design based on a high infiltration rate (design loading rate or DLR) of 130mm/day. The current 2004 version of TP58 does not recommend high DLR’s for primary treated effluent. High infiltration rates in TP58 now require effluent to be treated to secondary standard prior to discharge to land.

Wastewater designer Stuart Challenger of Eliot Sinclair, recommended that the land application bed be upgraded to an AES treatment disposal system with effluent from the existing septic tank pumped to 6000L of additional septic tankage to match the expected additional inflow from the shower block and then be gravity fed to the AES treatment bed via a 4-port distribution box (a 7-hole box was actually installed for future-proofing). Provision is included for buffering the pump derived outflow through the septic tank prior to the distribution box, to be less than 76 litres/minute from each box port.

Lake Mahinapua DOC camping ground site

The new shower block will increase the daily flow from 30 to 50L per person. Peak design inflow for 300 people is 15,000L.

Inclusion of the grey water from the showers helps to dilute the effluent similar to domestic strength than the higher strength primary treated black water previously discharged. As the maximum design flow will be maintained for only a short period over Christmas / New Year, using an AES loading rate of 55L/m for the design of the AES bed was deemed appropriate. This was based on the tested performance of the AES system in Trial 12 at Rotorua’s OSET-NTP facility. During this trial at 200% loading for 5 days or 76L/m of AES pipe, there was no significant impact upon BOD, with TSS still maintaining A+ grading and minimal impact on nitrogen reduction.

At both the 38 and 76L/m loading AES is recorded at OSET performing better than almost all AWTS package treatment plants.

Click on the drawing below to enlarge.

Lake Mahinapua DOC campground AES wastewater system

The number of AES pipes required was 15,000L/55L per metre = 273m divided by 3m (length of AES pipes) = 91. The current location for the land application bed was about 20m long so with 6 pipes in each row the length of the AES bed would be 18.6m and the number of rows would be: 91/6 = 16 rows (actual rows would be 15.2 but as it is not recommended to have part rows, this was rounded up to 16). So the width of the bed is 16 rows x 0.45m per row + 0.45 for side clearance = 7.65m. The total area of the bed is therefore 18.6 x 7.65 = 142.3m2. This is a loading rate of 15,000L per day/142.3 m2 = 105mm/day.

This is a lower application rate than the previous 130L/day. The AES bed is located so that it can be extended lengthwise or sideways at a later date if required using the unused ports of the installed 7-port distribution box.

The septic tank capacity needed to be increased by a similar amount to the increase in inflow to have the capacity for 24 hours storage plus room for build-up of scum and sludge. i.e. 20L/person/day x 300people = 6000L. A 9000L septic tank was installed adjacent to the existing tank and above the beds to allow for future increased use. As the effluent is pumped to the additional septic tank it was recommended that the filter be removed from the existing tank to allow some of the solid matter through. From the new septic tank, the effluent flows by gravity to the AES bed. However, the outflow from this additional septic tank is at the same rate as the inflow so it was necessary to buffer the flow before it enters the AES bed. A 2m section of 200mm diameter pipe was installed prior to a 90-degree bend before the distribution box. Installation was managed by Duncan Hamilton of Dwan & Andrews from Hokitika.

Wooden staples securely hold the 4 rows of AES pipe split into 4 sections placed on a base of 300mm system sand ready for the surrounding and covering sand to be added. Access to the bed was only available from the far end. The staples were lifted and re-established as the construction of the bed progressed when the covering sand was flush with the top of the 150mm depth.
The completed AES combined treatment and disposal bed showing the raised connector pipework fitted to the offset adaptors on the ends of the sections of each pipe row. All venting was manifolded at the septic tank end. The work was completed with a 20-ton digger and 4 staff in 6.5 hours. The AES system sand was stockpiled about 20 metres distant from the end of the bed.

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 the accommodation, museum and restaurant. The owner chose AES because it is an environmentally friendly and cost-effective option that could be retrofitted 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 10 pipes with raised connectors between each row, providing 60m of treatment pipe length in each 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 cascading pipe beds
Pipe bed – wooden frame indicating system extension
AES wastewater treatment system
Joining pipes

Click on images to enlarge:


Wastewater treatment systems at Maraes often have to be designed to handle high loads for short periods of time, then cater to much lower ongoing demand. If the Marae were to have an event where 100 people came during the day and 25 of them stayed overnight, for three consecutive days, around 6,750 litres of wastewater could be generated each day. With large events, up to 55,000 litres of effluent could be generated in a single event and less than 1,000 litres/day on the next.

Onuku Marae on the Banks Peninsula hosts weddings, tangi, and every three years Waitangi Day celebrations. The solution at Onuku Marae was to install a smaller AES treatment and disposal system with containment storage tanks to hold the peak flows. The tanks then dispersed the effluent to the AES system over the following 14 days or longer depending on the off-peak flows in the days following the event. The footprint of the system was around 6 times smaller than the alternative, treatment/disposal beds and a dripper field, and the AES treatment bed could also be used as a parking area. The cost of installing an AES system and containment tank was considerably less than alternatives, with the bonus of no ongoing costs of power and servicing.

E2 Environmental’s Lindsey Blakie of Christchurch, in conjunction with AES design specialists Wastewater Design Ltd of Nelson, developed a suitable solution for a projected 55,000 litres over 3 days. The limited area for disposal 25 metres above the Marae buildings had Category 5 light clay soils and a nearby stream. Soils investigation established a maximum daily loading of 2,500 litres over this area.

The solution negotiated with ECAN incorporates a pump-fed 23,000 litre baffled septic tank draining to 55,000 litres of underground detention tank storage then to 166m2 of AES treatment/disposal bed. Flow controlled doses of 312 litres every 3 hours move the primary effluent to the bed using flow data provided by a Khrone Optiflux 2000 mag flow meter and N2P Controls timed control of two submersible single-phase pumps. Pumps operate alternately, with the level control provided by a Nivelco hydrostatic level transmitter and the 4 lines of the AES pipe in the bed are fed alternately via a 4-port indexing valve. Alarms are raised if one pump fails to operate, if the outlet filter becomes partially blocked or if the detention tanks reach 75% capacity. A telemetry unit sends SMS text messages to service and management and contingency plans are in place for mobilisation of a vacuum truck for possible but unlikely excess influent over the 75% storage capacity.

The 2016 Waitangi celebrations occurred 6 weeks after commissioning where 16,000 litres of influent was received on the day.

Onuku Marae AES wastewater treatment system installation
AES treatment bed
Onuku Marae AES wastewater treatment system installation
Installing the AES pipes in a curved formation
Onuku Marae AES wastewater treatment system installation
Holding tanks
Oraka Aparima Runaka

A smaller AES system was installed at the Oraka Aparima Runaka building near Monowai. Here an existing primary system was upgraded to an AES system due to a failing disposal field. There is a high water table in winter ‐ about 600mm below ground level at the site. A 1,000-litre pump chamber and pump were added to lift the effluent into the new AES treatment and disposal bed. The bed is in a bund above the ground covered in topsoil and planted with native grasses. The existing septic tank is 10,000 litres and accommodates the peak flows. A number of people attend the camp when they have a function, or camp‐overs, 3‐4 times a year but no one is permanently living in the complex.

Lined AES bed installed for house near water & using treated discharge for irrigation

AES systems are usually installed with the treatment bed in an excavation in the receiving soil. In some conditions and situations however it may be installed in a lined bed. Lined beds are installed when:

  1. The design loading rate of the receiving soil is less than 10mm/day such as Category 5 Weakly Structured or Massive Light Clays and Category 6 clay soils. The treated effluent from the lined bed is then drained to a siphon or pump chamber for disposal with pressure compensated drippers.
  2. The treated effluent is used for irrigation or other water reuse.
  3. There is a requirement for additional nitrogen / nutrient reduction which involves recirculating treated effluent and / or tertiary treatment to remove potential pathogens.

The owners of a 3 bedroom and office dwelling in the Tasman District were constrained by the resource management plan to a design infiltration rate of 2mm/day due to being in a Wastewater Management Area and having category 6 clay soils. They also wished to reuse their wastewater for landscaping irrigation on a relatively dry site. Reliability of this system using pressure compensated drippers required a minimum level of secondary treatment. An AES wastewater treatment system was selected, designed by Wastewater Design Ltd and installed by Laser Plumbing, both of Nelson.

The AES lined bed system pumped to irrigate grasses and plantings provides an attractive feature in the landscaping of the section.

The design included:
AES Bed – 6.6m x 3.3m; base area 21.8m2

The 6.6m long AES bed included 6 rows of AES pipes connected in series, installed in AES system sand. The sand under, around and over the pipes was sourced from a nearby supplier processing river gravels. Most local sands destined for concrete manufacture will comply. The bed lining was 500mu polythene over Bidum A14 filter cloth. The base of the bed was shaped to fall towards a 100mm DWV pipe with 4mm drilled holes at a 4 and 8 o’clock position installed over the central depression collecting the treated effluent falling to a pump chamber. A nominal 50mm thick layer of pea metal was provided between the base of the AES system sand and the round river gravel derived drainage metal surrounding the underdrain pipe laid on the polythene liner. The venting system of the AES bed was terminated using the house for support above the roof eve 3 metres vertically above the vent at the bed.

Disposal Field – 540m2
32mm LDPE header line fed a manifold splitting to 5 x 16mm diameter pressure compensating dripper lines. Each line has inlet isolation so that individual lines can be isolated for flushing and a similar valve at the line end for flushing. End valves were installed in a valve box. Dripper line emitters were Unibioline 16010 CNL 1.6L/hr @ 0.6m centres.

Retrofit to Upgrade an Existing System

The wastewater treatment system at a 3 bedroom holiday home with rainwater storage tanks on a flat 900m2 section near the water was required by the Regional Council to be upgraded. The existing primary treatment system comprising a septic tank and a single soakage trench had an overflow to a roadside drain, thereby having an effect beyond the property boundary. The soils are Category 5 clay and sand beneath topsoil. Groundwater was located within 0.6m and surface water within 15m from the disposal field requiring a resource consent. Soil category and site constraints meant a Secondary Treatment System was needed.

The owners asked for an AES system which was designed by Matthew Hargood of Richardson Stevens Consulting Engineers and installed by Russ Louie of Bay Plumbing Services. Designed for 725 litres per day (5 people using 145L/day) and using standard water reduction fixtures, the AES pipes were installed in a 75m2 base area raised bed to achieve 0.6m clearance to ground water. Section planting helps reduce subsurface loading. The installers said it was by far the most suitable system for this situation being coastally sensitive, a substantial dwelling on a small site with a high water table and not easily accessible being up a right of way.

A Large scale Town AES installation – 200,000L 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 groundwater. 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 chose the Advanced Enviro-Septic® (AES) 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 faecal coliforms it surpassed the standards required. AES 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 2,500-88,000 gallons per day (GPD).

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 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

New system provides wastewater treatment solution for FEMA workforce housing in Paradise, California.

Written by Don Prince

The November 2018 Paradise, California Camp Fire in the Sierra Nevada foothills devastated the entire community, killing 85 people, destroying 11,000 homes, and displacing nearly 50,000 people. It was the most destructive wildfire in the history of California.

Paradise Fires

After the fire was subdued, it left a devastated community. This disaster required an immediate response from the Federal Emergency Management Agency (FEMA) including manpower and equipment to quickly stabilise the situation, clear debris including toxic waste, and rebuild the community. To facilitate this massive recovery effort, the creation of a nearby workforce housing camp for up to 1,500 workers was necessary. The former Tuscan Ridge Golf Club property was selected for the base camp facilities, which consist of approximately 400 temporary, modular housing units, two food preparation kitchens, a dining facility, a fitness and recreation centre, and a full-service laundry. To proceed with the base camp construction, a wastewater treatment system design with the capacity to handle a design flow of up to 100,000 gallons per day (GPD) was needed.

Project Challenges

Accelerated deadlines and extreme site limitations complicated the Tuscan Ridge Base Camp and wastewater system construction. The wastewater design flow was calculated at 50 GPD for each of the potential 1,500 workers for a total of 75,000 GPD. To accommodate peak flows and a factor of safety, the wastewater system design was sized for flows up to 100,000 GPD. Site geologic conditions were challenging. Underlying shallow lava formations precluded subsurface dispersal and impeded the installation process. Trenching through the solid rock at the site required specialized construction equipment.

Time was in short supply as modular worker housing was being constructed quickly. To expedite the construction timeline, a General Order Permit was issued to speed regulatory approvals for the wastewater system. Due to the challenging characteristics of the site, large wastewater flows, and short timeframe for completion, the project contractor, Lance Bates of NexGen Septics, selected an Advanced Enviro-Septic (AES) Wastewater Treatment System. The AES system features gravity collection and distribution, passive secondary treatment, ultraviolet (UV) disinfection, and large evapotranspiration basins for post-treatment dispersal and possible reuse. The AES technology removes 99 percent of wastewater contaminants and requires a minimal amount of ongoing maintenance.

Wastewater System Details

Wastewater is collected from the housing, laundry, and kitchen facilities including from the inline grease interceptors specified for the food preparation areas. The wastewater flows by gravity to primary treatment in four Xerxes 40,000-gallon septic tanks that are plumbed in serial configuration for a total capacity of 160,000 gallons. Following the septic tanks, the wastewater discharges by gravity to a series of distribution boxes (d-boxes). The primary d-box splits the wastewater flow to four, lined, Advanced Enviro-Septic (AES) beds, which perform passive, secondary treatment. Each bed has a design flow capacity of 25,000 GPD and contains 8,400 feet of AES pipe surrounded by specified sand. The entire system, including the four identical beds, totals 33,600 feet of AES pipe. The treated effluent is collected from the bottom of each bed and is distributed by gravity to four Salcor 3G UV disinfection units. There is a total of 16 UV units and each four-unit array disinfects 25,000 GPD. The purified effluent is distributed by gravity to one of four pump tanks. The effluent path through the bed, UV units, and pump chamber is segregated to allow isolation of the flows for any maintenance such as UV lamp replacement, etc. Lastly, each pump chamber distributes the purified effluent up to two evapotranspiration ponds.

Paradise Today

Before the availability of the Tuscan Ridge Base Camp, FEMA recovery workers had to travel long distances to and from the area each day due to a lack of accommodations. This workforce camp is expected to continue as an active staging and housing area for the Camp Fire recovery efforts throughout Butte County for the foreseeable future.

The impact of the fire on the Town of Paradise is reflected in the population, which dropped from 26,800 in 2010 (United States Census, 2010), to approximately 2,000 residents in April 2019. This decrease in population enabled the State of California to certify the community as a rural area, which allowed the town to receive additional funding for housing, wastewater projects, and other needed rebuilding efforts. New building codes addressing flammable materials and improved street planning are being incorporated into the recovery plans to prevent similar devastation in the future.

While some residents have left the area without any plans to return, others are committed to rebuilding their homes utilizing fire resilient building practices; with many choosing concrete exteriors and incorporating additional safety features such as sprinkler systems. Businesses are beginning to reopen and there is widespread hope that the town and greater community will emerge from this disaster stronger, safer, with a more modern municipal infrastructure, and better able to meet the economic and environmental challenges of the future.

Don Prince holds a Civil Engineering Degree from Vermont Technical College and is a licensed septic system designer and evaluator. He has provided technical support for AES and other Presby Environmental products since 2012. Presby Environmental is an Infiltrator Water Technologies company.