Disinfection is the last step for all levels of treatment, and uses chlorine and/or ultraviolet light to deactivate microorganisms.
Learn about our water resource recovery facilities, and how they treat wastewater before it's recycled, reused, recovered or discharged to waterways.
How we treat wastewater
Our water resource recovery facilities use multiple processes to treat wastewater for reuse or return to the environment. We ensure it meets strict water quality requirements to use as recycled water or releasing it to creeks, rivers and the ocean.
The treatment process and water quality required depends on:
- whether it will be supplied and used as recycled water
- where the treated wastewater will be discharged or reused.
We follow strict Environment Protection Licence (EPL) conditions issued by the NSW Environment Protection Authority (EPA).
The EPA monitors the effect of the treated wastewater that we discharge on water quality and aquatic life.
Find your local water resource recovery facility on our wastewater systems map.
Treatment processes
There are 4 main types of treatment processes, plus disinfection.
Primary treatment removes large solids and grit from wastewater.
Screens trap and remove things such as food scraps, wet wipes, cotton buds and plastic as wastewater flows through.
Grit tanks cause small, heavy particles like sand (grit) to sink to the bottom of a tank and a scraper removes it.
Sedimentation tanks allow solids (sludge) to settle to the bottom, and oils and grease (scum) float to the top. Scrapers at the top and bottom of the tanks remove the sludge and scum, which are then treated to produce biosolids.
Primary treatment at Wollongong
We use microorganisms (activated sludge) to break down organic material and nutrients like nitrogen and phosphorous.
Learn more about Removing nutrients in wastewater.
Next, we separate the activated sludge from the treated wastewater, as smaller organic solids settle at the bottom of the tank.
Secondary treatment at Cronulla
Tertiary treatment removes nearly all biodegradable and suspended matter to further improve quality. This process removes finer particles and reduces nutrients to very low levels.
Tertiary treatment at Rouse Hill
Advanced tertiary treatment uses ultrafiltration or microfiltration membranes to remove finer particles and reduce nutrients even lower.
Reverse osmosis uses fine barrier membranes at high pressure to improve the water quality even further, including removing dissolved salts.
What's inside a microfiltration membrane
How we reuse wastewater and recover resources
We use conventional and advanced technologies at our water resource recovery facilities to treat and reuse wastewater and recover resources.
Nearly all of our facilities either produce recycled water, reuse by‑products, or generate energy. Some do all three.
We're committed to reducing our environmental impact and helping to address climate change.
What we produce
Recycled water produced from wastewater is treated so it’s safe and appropriate for its intended use. The recycled water we produce at our water resource recovery facilities can be used:
- in homes and businesses
- for irrigation
- in industry
- for firefighting and dust suppression
- to supplement environmental flows and improve waterway health.
We manage and monitor our recycled water to ensure it meets the Australian Guidelines for Water Recycling (ADWG) and NSW Health requirements.
Our water resource recovery facilities reuse treated wastewater on their site to help save drinking water.
Biosolids are a nutrient-rich fertiliser created from the organic wastewater solids (or sludge), during the wastewater treatment process. They're a rich source of phosphorus and nitrogen and can be used in agriculture, forestry, composting and land rehabilitation.
Using biosolids in land applications is highly regulated, and we comply with all testing and reporting requirements set by the EPA.
Producing biosolids helps us reduce our environmental footprint by:
- recycling a valuable resource that helps minimise disposal to landfill
- reducing the amount of chemical fertilisers used on farms
- producing carbon-neutral biogas to generate renewable energy, to help power our water resource recovery facilities.
We're NSW's largest producer of biosolids, generating nearly 200,000 wet tonnes of biosolids from wastewater each year – that's equivalent to about 9,000 semi-trailer loads.
We generate renewable energy at our water resource recovery facilities. We recover this energy in different forms, including electricity and gas.
Hydroelectricity
At our North Head Water Resource Recovery Facility, we generate hydroelectricity by capturing energy from treated wastewater as it flows to the deep ocean outfall.
Solar energy
As part of our commitment to achieving net-zero emissions, we have installed solar panels and solar hot water systems at several of our water resource recovery facilities. We will also continue to invest in solar systems across our facilities to generate and harvest solar energy.
Power generated from solar panels supplies electricity to operate parts of our facilities.
Biomethane (renewable gas)
We've partnered with Jemena to install a biogas upgrader at our Malabar Water Resource Recovery Facility.
Excess biogas not used for co-generation is further treated to produce renewable gas (biomethane), that can be supplied to Jemena's customers via the local gas network.
What we do at each facility
Nearly all of our facilities recycle water, reuse by-products, or generate some of the energy they need to do their job. Details in the table below are current for 2024–2025.
ML = megalitres, or million litres
Less than 1% of Sydney's wastewater is discharged to the ocean untreated, at Vaucluse, Diamond Bay and Diamond Bay South. The Refresh Vaucluse Diamond Bay project will ensure that all wastewater is treated at Bondi Water Resource Recovery Facility in the future.
| Facility | Wastewater treatment level | Recovered resources | Avg. dry weather discharge of treated wastewater to waterway | EPL waterways discharge volume limit1 | Treated wastewater – waterway discharge location | Recycled water – type of use, supply location, waterway discharge location |
|---|---|---|---|---|---|---|
Bellambi2,3 | Primary (stormwater management) | N/A | 0 ML/day | Refer to Wollongong | Bellambi Point during wet weather. | N/A |
Bombo | Secondary | Recycled water Biosolids | 4 ML/day | 45 ML/day | Bombo Point as ocean outfall. | Supplied to and used at Kiama Golf Club. |
Bondi | Primary | Biosolids Renewable energy | 113 ML/day | 680 ML/day | As deepwater ocean outfall 2.2 km from the shoreline with 63 m maximum water depth and 512 m diffuser zone. | N/A |
Brooklyn | Tertiary | N/A | 0.3 ML/day | 2.1 ML/day | Hawkesbury-Nepean River at 14 m depth – located on second pylon of the old road bridge, adjacent to Kangaroo Point. | N/A |
Castle Hill | Tertiary | Recycled water
| 5.7 ML/day | 80 ML/day | Cattai Creek. | Supplied to and used at Castle Hill Country Club. |
Cronulla | Tertiary | Biosolids Renewable energy | 55.3 ML/day | 432 ML/day | Potter Point, Kurnell, as ocean outfall. | N/A |
Fairfield2,4 | Primary | N/A | 0 ML/day | Refer to Malabar | Occasional discharge to Georges River via Orphan School Creek during wet weather. | N/A |
Gerringong-Gerroa | Tertiary | Recycled water | 0 ML/day | 0.8 ML/day (sand dunes) | Sand dune systems. When the discharge volume limit to sand dunes reaches capacity, discharges go to Crooked River. | Used for agricultural irrigation at Aorangi Farm. Excess discharged to sand dunes. When the discharge volume limit to sand dunes reaches capacity, discharges go to Crooked River. |
Glenfield4 | Secondary | Biosolids Renewable energy | 0 ML/day | Refer to Malabar | Transported to Malabar. Occasional discharge to Georges River in wet weather. | N/A |
Hornsby Heights | Tertiary | Biosolids | 6 ML/day | 85 ML/day | Berowra Creek via Calna Creek. | N/A |
Liverpool4 | Secondary | Recycled water Biosolids Renewable energy | 0 ML/day | Refer to Malabar | Transported to Malabar. Also supplied to Fairfield (operated by Aquanet and Veolia Water) under Rosehill Recycled Water Scheme. Occasional discharge to Georges River in wet weather. | Supplied to and used at Liverpool Golf Club and Warwick Farm Racecourse. |
Malabar | Primary | Biosolids Biogas Renewable energy | 493 ML/day | 1,199 ML/day | As deepwater ocean outfall 3.6 km from shoreline – with 82 m maximum water depth and 720 m diffuser zone. | N/A |
North Head | Primary | Biosolids Renewable energy | 345 ML/day | 1,400 ML/day | As deepwater ocean outfall 3.8 km from shoreline – with 60 m approximate water depth and 763 m diffuser zone. | N/A |
North Richmond | Secondary | N/A | 1.2 ML/day | 11.2 ML/day | Hawkesbury-Nepean River via Redbank Creek. | N/A |
Penrith5 | Tertiary | Recycled water Biosolids | 24.7 ML/day | 238 ML/day | Excess designed to be discharged via Boundary Creek to Hawkesbury-Nepean River. | Most recycled water transferred to St Marys Advanced Water Treatment Plant. Also supplied to and used at Penrith City Council parks and sports fields. |
Picton | Tertiary | Recycled water Biosolids | 2.5 ML/day | 15 ML/day | Precautionary treated wastewater and wet weather overflows discharged to Stonequarry Creek. | Supplied to and used at Picton Farm. |
Port Kembla2,3 | Primary (stormwater treatment) | N/A | 0 ML/day | Refer to Wollongong | Red Point headland during wet weather. | N/A |
Quakers Hill | Tertiary | Recycled water | 41.3 ML/day | 281.2 ML/day | Excess discharged via Breakfast Creek to Eastern Creek. | Supplied to and used at Stonecutters Ridge Golf Club. |
Richmond | Tertiary | Recycled water Biosolids | 1.5 ML/day | 20.1 ML/day | Excess discharged to Rickabys Creek. | Supplied to and used at University of Western Sydney (Hawkesbury Campus) and Richmond Golf Club. Also used to irrigate our Eucalyptus plantation next to the facility (used by Taronga Zoo). |
Riverstone | Tertiary | Biosolids | 15.4 ML/day | 104 ML/day | South Creek via Eastern Creek. | N/A |
Rouse Hill | Tertiary | Recycled water Biosolids | 19.8 ML/day | 151 ML/day | Excess discharged to Second Ponds Creek via wetlands to Cattai Creek. | Supplied to homes and businesses in the Rouse Hill area for non‑drinking use. |
Shellharbour | Secondary | Biosolids | 19.6 ML/day | 170 ML/day | Discharged via an offshore outfall 130 m from Barrack Point with a diffuser zone. | N/A |
St Marys5 | Tertiary | Recycled water Biosolids Renewable energy
| 29.6 ML/day | 250 ML/day | Excess discharged to South Creek via an unnamed creek.
| Most recycled water transferred to St Marys Advanced Water Treatment Plant. Also supplied to and used at Dunheved Golf Club. |
St Marys Advanced Water Treatment Plant5 | Advanced tertiary | Recycled water | 50 ML/day | 55 ML/day | Environmental flows discharged to Boundary Creek under the Western Sydney Replacement Flows Recycled Water Scheme. | Facility receives tertiary treated recycled water from St Marys and Penrith to produce highly treated advanced tertiary recycled water. |
Wallacia | Tertiary | Biosolids | 1 ML/day | 15 ML/day | Discharged to Hawkesbury-Nepean River via Warragamba River. | N/A |
Warriewood | Secondary | Biosolids Renewable energy | 17.4 ML/day | 125 ML/day | Discharged at Turimetta Head via ocean outfall. | N/A |
West Camden | Tertiary | Recycled water Biosolids | 21.8 ML/day | 120 ML/day | Excess discharged to Hawkesbury-Nepean River via Matahill Creek. | Supplied to and used at Elizabeth Macarthur Agricultural Institute, Glendon Brae Pastoral Company and A Smart Farmer. |
West Hornsby | Tertiary | Biosolids | 12 ML/day | 154.3 ML/day | Berowra Creek via Waitara Creek. | N/A |
Wilton | Tertiary | Recycled water Biosolids | 0 ML/day | 3 ML/day | Occasional discharge to Stringybark Creek. | Supplied to homes and businesses in Bingara Gorge estate for non‑drinking use. Also supplied to and used at Bingara Gorge Golf Course, as well as parks and green space within the estate. Excess occasionally discharged to Stringybark Creek. |
Winmalee | Tertiary | Biosolids | 18 ML/day | 330 ML/day | Hawkesbury-Nepean River via an unnamed creek. | N/A |
Wollongong | Tertiary and Advanced tertiary | Recycled water Biosolids Renewable energy | 36.3 ML/day | 320 ML/day | Excess discharged at Coniston Beach as offshore ocean outfall. | Tertiary treated recycled water supplied to and used at Port Kembla Coal Terminal, Wollongong Golf Club and Wollongong City Council sports fields. Advanced tertiary treated recycled water supplied to and used at BlueScope Steel. |
Table notes
- Discharge volume limit is specified in environment protection licence issued by NSW Environment Protection Authority (EPA).
- Bellambi, Port Kembla and Fairfield facilities only receive flow during storm events.
- Port Kembla and Bellambi facilities are part of the Wollongong system.
- Fairfield, Glenfield and Liverpool facilities are part of the Malabar system.
- St Marys Advanced Water Treatment Plant is not in use while restoration work is being completed at Boundary Creek. Treated wastewater discharged during dry weather from Penrith and St Marys facilities is being diverted to an unnamed creek that flows to South Creek.