North Head Water Resource Recovery Facility

Treating wastewater

The North Head Water Resource Recovery Facility is about 30 water resource recovery facilities in Greater Sydney. Here, we treat water to a primary standard before releasing it to the ocean via a deepwater ocean outfall.

Facts and figures

Location: Bluefish Road, Manly.

Population served: 1 million people.

Area served: 452 square kilometres, including from Seven Hills in the west, south to Bankstown and north to Ku-ring-gai and Collaroy.

Wastewater treated: 336 million litres each day.

Treatment level: Primary.

Environmental discharge: We release the treated wastewater to the ocean using a deepwater ocean outfall. The deepwater ocean outfall is 3.6 kilometres from the shoreline, 82 metres maximum water depth and has a diffuser zone of 720 metres.

Biosolids produced: 12,000 tonnes each year.

Operating licence and regulation: We operate the facility under 2 sets of rules:

Technical resources
North Head Wastewater Treatment Plant technical data – technical specifications for the facility
What's in wastewater? – common wastewater parameters
Removing nutrients in wastewater – fact sheet

Flow chart

Primary treatment

Primary wastewater treatment removes large solids using physical separation processes. Most of the solids removed can be treated for beneficial reuse.


Screens trap and remove large solids as wastewater flows through.

Grit removal

We inject air into a tank, causing the water to spiral. The air flings grit such as sand and coffee grounds to the edges. It collects in the bottom of the tank where a scraper removes it.


Sedimentation tanks allow solids to settle to the bottom of the tank, while oil and grease float to the top. Scrapers at both the bottom and the top of the tanks remove the solids, oil and grease, which are then treated to produce biosolids.

We use sedimentation tanks to remove solids, oil and grease.

Releasing the water

Most of the treated wastewater is discharged to a deepwater ocean outfall. It enters a large tunnel that carries it under the seabed about 3.6 kilometres out to sea, where the ocean is about 60 metres deep. The deepest point is 82 metres.

The wastewater is released into the ocean through diffusers. The diffusers are spread over about 720 metres at the end of the tunnel into an area off the eastern seaboard that is naturally swept by currents flowing north to south.

Sunlight, saltwater and wave action work together to naturally break down and disinfect the treated wastewater.

We monitor the marine environment and test for toxicity to check for any impact. We continue to work with the NSW Environment Protection Authority to study the marine environment around the deepwater ocean outfalls.

Some wastewater is further treated and reused in the facility as cooling water and to flush equipment.

Treated wastewater from North Head is discharged to the ocean.

Renewable energy generation

We're constantly looking for ways to reduce our carbon footprint and use alternative and renewable energy sources. At North Head, we produce up to 58% of the facility's total energy needs from renewable sources.

Learn more about energy management and climate change.


We have a hydroelectric generator at North Head Water Resource Recovery Facility.

The treated wastewater falls down a long drop shaft on its way to the deepwater ocean outfall. The falling water has enough kinetic energy to drive a water-powered generator, producing hydroelectricity.


At North Head, we use cogeneration to meet some of the facility's energy needs.

We capture methane gas (biogas) from the anaerobic digesters and use it to power a combustion engine that drives an electricity generator.

The cogeneration engine turns biogas into energy and heat.

Operations and maintenance

Running the facility

A team of staff manage, operate and maintain the facility. They collect and analyse water samples, do laboratory testing, and manage special projects to keep it running safely and efficiently.

Maintaining the facility

Three types of maintenance are required to keep the facility operating: preventative, planned and reactive.

See the table below for examples.

Staff monitor the facility to make sure it's working at its best.

Maintenance type




Prevents a breakdown

Oiling a motor


Replacing equipment as it reaches the end of its useful life, before a breakdown

Replacing a worn motor


Fixing equipment that has unexpectedly broken down

Repairing a motor

Kinetic energy

The energy that an object possesses by virtue of its motion.


Electricity made from falling water turning turbine generators.


Cogeneration is the production of heat and energy at the same time.