Liverpool to Ashfield Pipeline

Sydney Water and the NSW Government have clearly been working hard to identify new opportunities for water recycling. The 2006 Metropolitan Water Plan describes some major schemes currently under development. These include supplementation of environmental flow in the Nepean River (Western Sydney Recycled Water Initiative); significant expansion of dual-reticulation schemes in north west and south west growth centres; and a major industrial reuse scheme (Bluescope Steel, Wollongong).

However, there is one opportunity which, although it is right under our noses, seems to be eluding all attention. So let me tell you about the Liverpool-to-Ashfield pipeline.

Sydney Water workers recently began boring a 20-metre hole into a reserve at Park Road, Ashfield. This is part of a$110-million project to build a 24 kilometre pipeline from Liverpool, a major component of the South Western Sydney Sewerage Scheme.

Two of Western Sydney’s largest inland sewage treatment plants are at Glenfield and Liverpool. Together these produce more than 50 megalitres of tertiary treated effluent per day. Historically, effluent from this area was discharged into the Georges River. However, to improve the water quality in the river, this practice has been largely discontinued. Instead, the treated effluent is dropped straight back into the sewer, where it is mixed with raw sewage and flows all the way to Malabar. At Malabar, the mixture then undergoes primary treatment before being discharged via the deepwater ocean-outfall.

Click on the map for a larger image

South West Sydney is a major growth area and increased capacity is required in the north Georges River sewerage sub-main to allow for development. The aim of the Liverpool-to-Ashfield pipeline is to free up capacity in this sub-main by diverting flows from the Glenfield and Liverpool sewage treatment plants.

The pipeline would carry tertiary-treated effluent 24 kilometres through some of Sydney’s most densely populated suburbs and industrial areas. However, when the water reaches Ashfield, it will again be dropped back into the old sewer, where it will again be mixed with raw sewage and transported to Malabar for discharge.

The pipeline is due for completion in 2008 but future options for reusing the treated effluent are not intended to be considered until 2010. This is a short sighted decision that should be revisited as a matter of urgency.

The Liverpool-to-Ashfield pipeline is new infrastructure and as such, provides a unique opportunity for planning for access to the recycled water. Expressions of interest should be sought immediately from local government and industrial water users to make use of this water as a replacement for current potable-water use. Obvious examples include irrigation of public parks and playing fields. There is also considerable heavy industry in the areas around Liverpool, Bankstown and Strathfield. If such interest is sought, this would allow Sydney Water to optimally plan the pipeline before it is completed and rendered inaccessible or unsuitable for access. Planning should include identification of the optimum precise path for the pipeline, any additional branches that may facilitate access, and the implementation of usable access junctions. The diameter of the pipeline should also be carefully considered to provide for optimum flow regimes facilitating access.

Under normal circumstances, ideas for sewer mining are commendable. However, in this case, we are dealing with water that has already had considerable energy-investment in bringing it up to a tertiary-treated quality. It seems sheer madness to throw that away by then mixing it with raw sewage. Our aim should be for nothing more than a trickle of water to actually reach the sewer junction at Ashfield. Come on NSW, let’s do something novel and plan before we build!