Sydney's affluent eastern suburbs have raw and untreated sewage from 3,500 people discharged directly into the Tasman Sea.

Australians love our iconic coastal lifestyle. So many of our settlements are spread along our huge coastline. Real estate prices soar where we can catch a view of the water.

But where there are crowded communities, there is sewage. And along the coast it brings a suite of problems associated with managing waste, keeping the marine environment healthy, and keeping recreational swimmers safe.

Sewage is not a sexy topic. People often have an “out of sight, out of mind” attitude. But where does sewage go, and is it treated and disposed of in the waters that we Australians love?

The bigger the coastal community, the bigger the volume of sewage. Disposal of human waste into the ocean might solve one problem, but we now realise that the “waste” is as precious as the ocean it pollutes.

Sewers leading into the water

We should be treating and recycling sewage to a drinkable level.

Understanding the problem from a national perspective

Such problems play out continuously along our coastline. Each isolated community and catchment issue arises and is resolved, often in ignorance of and isolation from similar issues somewhere else.

At present, places where sewage impacts are generating community concern include MerimbulaWarrnambool and, perhaps most bizarrely, Vaucluse and Diamond Bay in Sydney’s affluent eastern suburbs.

It’s hard to believe this location has raw and untreated sewage from 3,500 people discharged directly into the Tasman Sea. Sydney Water pledged in 2018 to fix this unsightly pollution by transferring the flow to the nearby Bondi sewage treatment plant.

Community group Clean Ocean Foundation has worked with the Marine Biodiversity Hub to start the process of viewing outfall pollution – where a drain or sewer empties into the sea – as part of a bigger picture. It’s a first step towards understanding from a national perspective.

Together they have produced the National Outfall Database to provide the first Australia-wide comparison.

The best and worst offenders

Previously the information available to the public was sketchy and often not easily accessed. The database shows how differently Australia manages coastal sewage with information on the outfalls.

Clean Ocean Foundation CEO John Gemmill said:

Water authorities in the main do a great job with severe funding constraints. But they can be reticent to divulge information publicly.

One authority, suspicious of the research project, initially refused to give the location of the outfall, claiming it would be vandalised by enraged “surfies and fishermen”.

Sydney has Australia’s biggest outfall. It provides primary treatment at Malabar, New South Wales, and serves about 1.7 million people. The outfall releases about 499 megalitres (ML) per day of treated sewage, called “effluent”.

That’s about eight Olympic-sized swimming pools of effluent an hour. It is discharged to the Pacific Ocean 3.6 kilometres from the shoreline at a depth of 82 metres.

The cleanest outfall (after sustained advocacy over decades from the Clean Ocean Foundation) is Boags Rock, in southern Melbourne. It releases tertiary-treated sewage with Class A+ water. This means the quality is very suitable for reuse and has no faecal bacteria detected (Enterococci or E.coli).

Recycling sewage

Treated sewage is 99% water. The last 1% is what determines if the water will harm human and environmental health. Are we wasting a precious resource by disposing of it in the ocean?

As desalination plants are cranking up in Sydney and Melbourne to extract pure water from salty ocean, why shouldn’t we also recycle sewage?

Clean Ocean Foundation has released a report showing it would pay to treat sewage more thoroughly and reuse it. This report finds upgrading coastal sewage outfalls to a higher level of treatment will provide tens of billions of dollars in benefits.

Industry analysis suggests that, for a cost outlay of between A$7.3 billion and A$10 billion, sewage treatment upgrades can deliver between A$12 billion and A$28 billion in net benefits – that is, the financial benefits above and beyond what it cost to put new infrastructure in place.

Then there are non-economic benefits such as improved ecological and human health, and improved recreational and tourism opportunities by use of suitable recycling processes.

What the rest of Australia can learn from WA

Clean Ocean Foundation president Peter Smith said Australia’s key decision-makers now, more than before, have a “golden opportunity” to adopt a sea change in water reform around coastal Australia based on good science and sound economic analysis.

In the context of the drought of southeast Australia, recycling water from ocean outfalls is an option that demands further debate.

As expensive desalination plants are switched on, Sydney proposes to double the size of its desalination plant – just a few kilometres from massive ocean outfalls that could provide so much recycled water. And to our shame, NSW ocean outfalls are among the lowest in standards of treatment.

Western Australia, on the other hand, leads the push to recycle wastewater as it continues to struggle with diminishing surface water from climate change.

In fact, in 2017 the Water Corporation announced massive investment in highly treated sewage being used to replenish groundwater supplies. Perth now sources 20% of its drinking water from groundwater, reducing its reliance on two desalination plants. A key factor was successful engagement with affected communities.

The discharge of poorly treated sewage to rivers, estuaries and oceans is a matter of national environmental significance and the Commonwealth should take a coordinating role.

Our oceans do not respect state boundaries. The time is ripe for a deliberate national approach to recycling sewage and improved systems to manage outfalls.

This article is republished from The Conversation under a Creative Commons license. Read the original article.


  1. We have to make Tertiary treatment mandatory. The BVSC as per your linked article has decided to push the outfall botton claiming cost prohibits treatment. I understand the issue with capex however if we look more closely at the issue and press the argument of CSO (obligation), then there is real leverage given the influx to population (perhaps 5 fold) and any shire councils inability to “tax for toilets”. This should become a federal issue, given the results of outfall and ocean currents nor tourists respect boundaries. There is a recently formed group in Merimbula that might benefit from discussions with Dr Blackwell and Mr Gemmill.


  2. It’s not just the water we need, it’s the phosphorus for fertiliser, too. Makes sense to send the wastewater inland to agricultural areas to combine the water/phosphorus benefits because it’s not just a water crisis, the soils are degraded, and the runoff from phosphate rock and cow manure enters the ocean – another pressure for the GBR catchment area on top of climate change (hello hypoxic dead zone).

    As for desalination- that kills more marine life by sucking the poor fellows up and then returning the briny water and chemicals – and aren’t they suffering enough, from effluent and plastic pollution, sea bed mining, things that go bang in military training and depth sounders or whatever – oh, and demersal and longline fishing? I don’t have a degree I must be stupid. What the hell is wrong with this world? Why isn’t something being done? Why wasn’t it done in 1972 at the Conference on the Human Environment? Or after silent spring? What was that I heard? Money, greed and the breakdown of community? I don’t want to breed, or overeat, I just want to pat fluffy animals, walk in the mountains and along the rivers and watch birds and butterflies. Must be something wrong with me.

  3. Canberra have been developing a product called AgriAsh for years – its removal is contracted out and it is then used for land fertiliser.

  4. Interesting Article:
    I have a series of queries. Where is the effluent from our inland cities going?

    Canberra and Queanbeyan both discharge into the lower Molonglo water treatment facility.
    This facility then discharges in the lower Molonglo River, which inturn runs into the Murrumbidgee River.

    With a parched inland – why do successive local governments and territories continue to ignore this resource?

    Come on Australia – we are smarter than that (flushing it out of sight and mind)
    There is employment opportunities – solar for power, steel for pumps and pipelines, and then there’s the compost for the renewal / replenishment of derogated lands.

    No brainer really – unfortunately it’s just not ‘sexy’.

    1. Hi Gordon, thanks for taking the time to read our blog. Our inland cities treat their effluent and then discharge into nearby rivers and streams being mixed and diluted by the water already in the rivers.

      Many local councils in small regional towns have already been recycling most or all of their wastewater for irrigating playing fields, parks and gardens. Those that have access to lots of water during plentiful times are less likely to recycle water until that water becomes unavailable. Many of these towns then have started recycling water.

      Research is starting to demonstrate that recycling wastes actually has long term economic, social and environmental benefits. As long as an appropriate circle of use of materials is put in place and appropriate treatment measures are used, it can be a win-win for everyone.

      CSIRO Social Media Team

  5. Absolutely spot on, our communal attitude to all water supply is completely destructive, not only economically, but socially & environmentally too, as the the Murray/Darling management fiasco clearly demonstrates. For a nation that is so chronically deficient in reliable, potable water & with a future so dependent on its availability, it’s well past time that these problems became part of a national imperative that replaces our current, short sighted political attitudes & issues with evidence based programs that focus on the long term maintenance of all our coastal & inland waters.

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