Who knows where the water goes?

“Water is a historical and current force that runs through, around and within North Head. Just as the historical significance of this place has left its mark on the present, large volumes of Sydney’s waste water continue to pass through the headland to be processed and then expelled and diluted within the ocean’s watery mass.” PhD Candidate Elizabeth Duncan explores the embedded materialities of Sydney’s waste water.

Image by Gameanna, via Shutterstock. ID: 131796455.

We are enmeshed within a watery world; water is touched, tasted, observed, absorbed and expelled by each of us every day. Our substance is a watery substance.

Ever since I was a child, my favourite part of the ferry trip from Circular Quay to Manly has always been passing through the stretch of water between South Head and North Head, the two headlands that form the mouth of Sydney Harbour. The size and treading pace of the ferry ride makes the ocean swell generally imperceptible to its passengers. But as the ferry passes through the brief stretch of water where the headland is parted to reveal the South Pacific Ocean, there is, even on a still day, a noticeable ocean swell. In these moments, the wateriness of the swelling harbour becomes perceptible in the bodies of the passengers.

North Head’s external face rises vertically from the ocean below. The ancient rock strata can be read as a layered, deep history of the headland. North Head is known by Aboriginal groups as Boree, Garungal or Car-rang-gel, names specific to the inner and outer sections of the headland.1 Historical investigation into the uses of North Head shows that the region has long been valued for its isolated and meditative qualities. For the Aboriginal people, the headland was a place of vital significance; a place for burial, healing and medicine. The Koradgee (wise ones) of local clans, would ceremonially use the land. Still now, remnants of this time reveal themselves; many sites of significance (including rock art, middens and burial sites) have been identified at North Head.

In the recent colonial past, the headland was put to many other uses. In the early 1830’s, Sydney’s first quarantine station was opened on the storied outcrop of land. The material legacy of the Manly Quarantine Station persists in its buildings, but also in the three quarantine cemeteries established while it was in operation. These cemeteries were progressively used for nearly a century.

In 1926 part of the Quarantine Station was apportioned for the Northern Suburbs Ocean Outfall Sewer. North Head was then the discharge point for the extensive sewage system reaching from Blacktown to Manly, completed in 1930.

During the Second World War, North Head was used as a heavily fortified military defence position, with tunnels, bunkers and look-outs remaining from this time. Above ground, the 1935 North Head Barracks and the 1946 Artillery School remain. All of these uses of the land, of Country, have left their traces, coalescing to form part of the layered history of North Head.

The North Head Waste Water Treatment Plant is still in operation and is a vital piece of infrastructure for Sydney. For this reason, students enrolled in a second year geography unit led by Dr Marilu Melo are visiting it as part of a field trip aimed at enhancing their understanding of the city; I’ve tagged along as an interested PhD student. Departing from the wharf, we make our steep ascent up Darley Road to arrive at North Head National Park. Walking through North Head, the air is a fresh and sweet smelling mixture of bush and ocean scents. Spotting a sign to the Waste Water Treatment Plant, we make a left and descend slightly down the hill to the boom gate, beyond which only registered personnel are allowed. Before we can see the plant, the smell of sewage catches the breeze; the materiality of our effluent thought to be flushed away returns to our senses.

The plant is embedded in the natural landscape. Its concrete mass is marked by protruding towers and large, stout, circular digesters, painted a bushy green to camouflage with the surrounding area. Metal boardwalks and neatly layered electrical wiring encase and intersect, the industrial landscape. Walking through the plant, the waste water is visibly still, sitting in long, open-air sedimentation tanks. We are told that birds will occasionally come to drink from these tanks.

While impressive, the plant’s above-ground form does not immediately communicate the sheer volume of its function.  North Head on average processes 336 million litres of waste water per day. Waste water refers to any used water, including stormwater that enters the pipe system in Sydney. The plant has a capacity to deal with 1100 million litres per day, a capacity that can occasionally be reached in storm events. The majority of North Head’s processing is completed underground, so it is only by seeing the plant underground that the awesome scale of the plant’s function can be even partly comprehended.

Descending into the core of the plant, we drive down the gaping tunnel to the deepest subterranean chamber. The chamber echoes with a dense soundscape: the noise of the large industrial pumps. Even in this subterranean setting, while the pumps and the larger processing machinery are visible to us, the spectators, the pipes themselves run beneath our feet encased in concrete and only assessable through trap doors.  In this enclosed setting, the smell of sewage is surprisingly no more perceptible than the smell above ground.  What is, however, amplified is the feeling of embodiment within the earth, within the very infrastructure of the city. There is an artificially lit twilight in these caverns; this world has its own rhythms, smells, sounds and maze-like geography; as we are lead around through doorways and passages, I am quickly disoriented.

The waste water enters the plant at this precise level. At this point, the incoming waste water incorporates a multitude of materials –solids, chemical, food waste, oils, plastic waste and essentially any items which have been discarded down our household or city drains. The water there is tested periodically for its PH level and chemical make-up, and is then processed to remove incidental items such as plastic waste. The waste water is pumped to the plants surface, where it is left to sit and be processed in the sedimentation tanks, where the fats and oils (“the scum”, as it’s referred to) are scraped from the top of the water while the solids are collected at the bottom of the tanks. These bio-solids are then extracted and processed in the anaerobic digesters on site, and the by-product is sold on for reuse. The remaining effluent is then discharged through a sizeable drop-shaft that leads to the ocean outfall, at a depth of 60 meters and 3.6km from the shoreline. The great volume of waste water processed, and the height from which is it discharged, generates hydroelectricity used to run the plant.

Water is a historical and current force that runs through, around and within North Head. Just as the historical significance of this place has left its mark on the present, large volumes of Sydney’s waste water continue to pass through the headland to be processed and then expelled and diluted within the ocean’s watery mass.

Water is itself a vessel through which things move. The flow of water through Sydney’s infrastructure is embedded with multiple materialities. Indeed our ‘modern’ sewage systems use water as a vessel through which to move our waste.  Ultimately this process leaves lingering questions about the equity of this modern exchange (between water use and waste water) and the traces that are left behind on water bodies.


1. Australian Museum. (2018). Aboriginal People of Coastal Sydney: Place name charts. Access here; Australian Government. (2018). Place details: North Head – Sydney, North Head Scenic Dr, Manly, NSW, Australia. Department of the Environment and Energy. Access here.

Elizabeth Duncan is a PhD candidate in the School of Geosciences at the University of Sydney.  Elizabeth has a Bachelor in Literature and Philosophy from the University of Notre Dame, and a Master of Sustainability from the University of Sydney. Her previous work experience has included time in the private and local government sectors, and as a research assistant within the School of Geosciences, University of Sydney. Elizabeth’s research project is titled: Verticality and volumes in motion:  the cumulative trajectories of waste. Focusing on waste, she is particularly interested in cumulative impacts of the materiality of waste and its movement through and beyond Sydney.

This blog is a part of SEI’s Student Blog Series, which features original content by Honours, Masters and PhD students at the University of Sydney who are undertaking research on environmental issues and topics. If you are a current postgraduate student at the University of Sydney who would like to participate in the series, click here for details.