Traditional wisdom in waste discharge is that:-
- public health is preserved by discharge of wastes entirely
to public infrastructure for remote treatment
- where such infrastructure does not exist, individual
'septic tank' systems are approved for discharge of all waste
to underground disposal
- where public infrastructure does exist, connection is
The assumptions in this approach are that:-
- the discharge is only waste and has no resource value
- public health are the only issues applicable
The development of other approaches to waste treatment has brought
to notice that:-
- concentration of waste treatment and disposal has
detrimental impacts on the environment
- some treatment processes add loads to the waste which add
further detrimental impacts to the environment, particularly chlorine
- collection of all wastes together results in large volumes
of wastecontaminated to the the lowest standard
- some wastes also contain resource value in their contents
or for re-use after treatment
The environmental objectives of waste treatment are to:-
- minimise the water volumes dedicated to these actions
- segregate wastes so that each can be treated effectively
with least inputs
- to re-use minimally polluted waters
- to harvest components in the waste water having resource value
- to segregate from human contact only hazardous waste waters
From this approach comes a waste treatment philosophy of:-
- keeping sullage, septic and trade wastes separate
- treating each appropriately
This practice’s best known project is the Easterbrook house at Kuitpo Forest. It also has a reed bed. This treats all wastewater except toilets and kitchen sink.
The outflow from laundry and bathrooms is settled in grease trap, then treated to denitrify and sieve suspended solids to create clarified water.
The treatment by reedbed uses varied species of reeds & grasses in the one bed:
left to right Phragmities Australis (reed), Juncus Paucifloris, Juncus Saraphorus (grasses), Louisiana Iris (water lily), Cyperus Vaginatus (reed)
The outflow is to storage and pumped distribution to garden drippers to the formal garden immediately around house perimeter.
Re-using treated waters from sullage for non-potable uses is achieved in reed beds in a number of further projects from this architectural practice embodying a variety of systems to achieve these goals:-
- The Wistow project uses split septic:sullage tanks with
treatment for discharge to underground disposal and grey water
holding and garden use.
- The Purnong project embodies compost toilet and separate
grey water system.
- The Lobethal cottage includes a compost toilet and grey
- The Teringie project incorporates septic discharge to
sewer and grey water treatment and use on-site. The S.A. Health
Commission believes it does not have the option to consider the
grey water system in the location with public sewer; but S.A.
Water Corporation have advised they have given the project
clearance to discharge septic but retain grey water on-site.
Waste water dispersal is difficult where soil horizons have low percolation.
In clay soils, most in-ground percolation methods result in saturated systems.
The ‘Wisconsin mound’ approach builds the dispersal system on top of the soil surface so that constant gravity injection pressure is created as well as horizons of storage above.
This practice constructed this method integral to the Packer house at Mundulla.
The owners have found that this construction was less costly than a larger in-ground disposal trench.
To Australian Standard 1547, the construction includes the scarifying and raking of the existing soil to maximise absorption, the sand bed of the mound with its gravel reception bed in the centre, the distribution pipes with their weep holes and storage capacity, with the wastewater being delivered from the treatment tank by submersible pump.
The whole is clay covered to avoid winter rain ingress, and perennial grass covering for erosion control.
This practice is also interested in the perimeter plantings to accept excess mound and run off rain waters by root take up and leaf transpiration.
While no credit for this is given in the calculations to the Standard, the work by CSIRO on in-soil watertable level control and community wastewater dispersal to wood lots (Tasmanian blue-gum plantations) gives encouraging data.