How it works

Wastewater Designers & Installers > How AES Works

How AES Works

AES How it Works Model

The AES System

The AES system works via passive ventilation through specially designed AES pipes which provide an environment for the micro-organisms in the effluent to break down to a very safe level. Simple, using the processes of nature, environmentally sustainable, scientifically proven and very effective.

The essential AES treatment process occurs in specially designed, 300mm diameter, oxygenated pipes installed in a sand bed in the ground. Effluent which flows via gravity into the AES pipe system from the septic tank is exposed to a culture of naturally occurring micro-organisms that break down solids and digest potential organic pollutants more rapidly in the presence of air.

The fabrics and fibres of the AES pipes provide a large surface to support the microbial life breaking down solids and digesting potential organic pollutants. An ample air supply through the pipe system and fluctuating liquid levels, as the usage varies during the day, increases aerobic bacterial respiration.


In order to achieve secondary wastewater treatment, an oxygenated environment is required.  AES system pipes achieve this by chimney effect venting also called differential venting. Air is drawn through a low-level inlet vent at the end of a line of AES pipes to a high outlet vent at least 3m above the low vent at the other end of the AES pipe system.

The AES bed venting is generally separate from the septic tank venting system.

The Specially Designed AES Pipes

The 300mm diameter pipes come in 3m sections easily joined together to create long or wide pipe system beds.
A mat of coarse, random fibres completely covers the pipes providing additional surface area for the microbial breakdown of solids and bacteria to take place. Skimmers on the interior capture grease and suspended solids from the effluent. Pipe ridges allow the effluent to flow without interruption around the circumference of the pipe. Bio-Accelerator™ fabric at the base of the pipe facilitates the development of a biofilm of self-colonising micro-organisms that process the organic material. By reducing permeability this biomat also ensures the effluent extends the entire length of the pipe.

This is a cross-section of an AES (Advanced Enviro-Septic™) pipe installed in a sand bed with an expanded section of the edge of the pipe superimposed: –

AES pipe ross section in sand

Stage 1:  Effluent enters the pipe and is cooled to ground temperature.  Suspended solids separate from the liquid effluent.
Stage 2:  Skimmers further capture the grease and suspended solids from the effluent.
Stage 3:  Pipe ridges allow the effluent to flow without interruption around the circumference of the pipe
Stage 4:  Bio-Accelerator™ fabric facilitates the development of a biofilm of self-colonising micro-organisms that process the organic material.
Stage 5:  A mat of coarse, random fibres provides additional surface area for microorganisms.
Stage 6:  Geotextile fabric, where biofilm reduces the permeability of the pipes, allows effluent to spread evenly along the pipes before seeping into the surrounding sand.
Stage 7:  Air space is maintained in the top of the pipes and passive ventilation enhances aerobic activity.
Stage 8:  Sand wicks liquid from the geotextile fabric and evenly distributes high quality treated effluent over the base of the bed.

System Sand is installed to a depth of 300mm below the AES pipes and 150mm above and between individual AES pipes. In less permeable soils the lower 150mm of the sand bed is extended horizontally to provide the required infiltration surface area. This is called a “Bed Extension”.

System Use

AES systems work best when one row is filled to overflowing rather than 2-3 rows partially filled. The last row will only receive effluent when there is peak occupancy in the home. Thus, when rows are connected in series, the first row is likely to receive more effluent than the last row. While this initially appears counter-intuitive to standard primary treated effluent dispersal to soil, there are benefits to the rising and falling of liquid in each row of AES pipe. This is referred to as the lung effect and provides optimal conditions for aerobic microbes as the liquid level rises and falls within the pipe system.

After around 21 days the aerobic micro-organisms have completely colonised the pipes and a stable community is established. A biomat is created which allows the effluent to extend the entire length of the pipe.

System Sand Bed

The remaining highly treated liquid is wicked out into a sand bed surrounding the pipes, evenly distributed over the base of the bed. The grain size of this sand allows effluent to travel slowly throughout the sand bed where there is further habitat for microbial breakdown. In this way, the base of the AES bed receives an even amount of effluent stripped of BOD and TSS to ≤ 2mg/100mls – 10x less than Secondary Standards confirmed by OSET-NTP test results.

Long Life

An AES system has a long life. Because of the structure of the AES system pipe, it does not suffer from progressive failure. The pipes are extremely durable and systems opened after 15-20 years have clean sand beds. This facilitates the working of water out of the AES system pipes and the introduction of oxygen into the micro-biological processes that also occurs in the sand.

AES components come with a 20-year guarantee. No other system provides this.

Designed in the USA

AES pipes and the AES wastewater treatment system has been specially designed in the USA by David Presby, an engineer with a lifetime of experience in the wastewater industry.