Disposal options for treated household wastewater

Homes with an onsite sewage management system have a Land Application Area (LAA) dedicated to the disposal of the treated wastewater. Wastewater from your home goes down the drain to the wastewater treatment system in your garden.

The treatment plant (septic tank or aerated system) processes the wastewater to reach a pre determined treatment level. This treated water is then dispersed to your garden via the LAA. The treated water is normally disposed of underground via irrigation, beds, or trenches. The size and type of disposal area varies from property to property.

What happens to the treated wastewater?

One of the most common and popular methods of disposal, is sub surface irrigation. This is rows of irrigation pipes laid in a network beneath your lawn. Sub surface irrigation (SSI) is very reliable and good for most locations. The network is normally about 300mm deep and is a great for keeping your lawn green.

The other most common system is ETA beds. ETA beds are a deeper disposal system that includes pipes and gravel. They are most often used for the poorer quality wastewater from septic tank systems. This method is also used to deal with sloped or terraced sites with poor soil permeability.

Other methods of disposal include trenches, Wisconsin mounds, and surface irrigation. These are not common and are normally used on sites with specific conditions or constraints. Trenches, or arch trenches, are good in compact areas with sandy soils. Wisconsin mounds are used for very compact sites or for properties in flood zones. The mound looks like a gentle rise in the lawn and still works if there is a flood.

Head to the Water NSW website and find out more about Subsurface Irrigation, ETA Beds, Absorption Trenches, Mounds and Surface Irrigation.

Top Left: Sub surface drip irrigation is the most common method of disposal for home sewage treatment systems.

Top Right: ETA beds are a good choice for sloped or terraced home sites, particularly if the ground is rocky.

Bottom Left: This LAA was designed for a very restricted site using absorption trenches.

Bottom Right: The disposal area for the treated wastewater on this home site was below flood level so a raised mound was construction for the LAA.

How is the dispersal method and LAA size decided?

Different houses produce different amounts of wastewater. The amount produced is based on the number of bedrooms (and potential inhabitants) in a house. Gardens will also absorb the water at different rates too. This will vary depending on things such as soils type, aspect, vegetation, and climate. A good wastewater system design is important to ensure the type and size of disposal area is the best for your property.

There are regulations on where disposal areas can go. They have to be a certain distance from buildings, waterways, and property boundaries. They are fine to be mowed and are good for a game of football. But they shouldn’t be driven over and horses or cows are not good for them.

Local council guidelines and regulations can dictate the type of disposal system as well. Many councils will not allow surface irrigation these days. This is due to health concerns and unreliability including lawn mower damage. Sub surface irrigation is preferred as it is safe and much more reliable.

A well designed and installed disposal area will last for years. You won’t even know it’s there. It efficiently disperses the water into the garden. Take care of yours, and what you put down the drain, and yours will last for years too.

Contact the team at True Water with any questions about your LAA.