North Head Biosolids Upgrade Project

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The North Head Water Resource Recovery Facility (previously known as the North Head Wastewater Treatment Plant) serves over one million Sydneysiders: from Seven Hills in the west, Yagoona in the south, and Ku-ring-gai and Collaroy in the north.

We’re building two new digesters and upgrading equipment to improve how we process biosolids at our North Head WRRF.


The biosolids project will:


Reduce odour

Improving the quality of the biosolids will make them less smelly. This means less odour as our trucks transport biosolids from North Head to farms in regional NSW.

Contribute to a circular economy

Recovering biosolids for reuse in agriculture helps reduce waste to landfill and contribute to a circular economy.




Produce better quality biosolids

Biosolids are used in agriculture to fertilise soil. Better quality biosolids will ensure we can continue to reuse 100% of the biosolids created.

Increase processing capacity

Two new digesters will increase sludge processing from 40 to 70 tonnes per day by 2043.




Improve reliability

In the long run, the new digesters and upgrades to sludge tanks will ensure the ongoing reliability of the facility








The North Head Water Resource Recovery Facility (previously known as the North Head Wastewater Treatment Plant) serves over one million Sydneysiders: from Seven Hills in the west, Yagoona in the south, and Ku-ring-gai and Collaroy in the north.

We’re building two new digesters and upgrading equipment to improve how we process biosolids at our North Head WRRF.


The biosolids project will:


Reduce odour

Improving the quality of the biosolids will make them less smelly. This means less odour as our trucks transport biosolids from North Head to farms in regional NSW.

Contribute to a circular economy

Recovering biosolids for reuse in agriculture helps reduce waste to landfill and contribute to a circular economy.




Produce better quality biosolids

Biosolids are used in agriculture to fertilise soil. Better quality biosolids will ensure we can continue to reuse 100% of the biosolids created.

Increase processing capacity

Two new digesters will increase sludge processing from 40 to 70 tonnes per day by 2043.




Improve reliability

In the long run, the new digesters and upgrades to sludge tanks will ensure the ongoing reliability of the facility







  • Concrete pour planned for 25 August 2022

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    We’ve completed two of the 10 concrete pours for the new digesters so far and our next pour is planned for Thursday 25 August, weather permitting. If we’re not able to complete the pour on Thursday, we will defer the work to Monday 29 August or Tuesday 30 August.

    We need regular deliveries of concrete throughout the day, so there will be frequent truck movements to and from the facility.

    This means some of our deliveries will be outside our standard working hours on that day, including:

    • during school zone hours (between 8 am and 9:30 am and 2:30 pm and 4 pm)
    • between 6 am and 7 am in the morning

  • Concrete pour planned for 24 June 2022

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    There are 10 major concrete pours planned over the next nine months to build the two digesters. We completed one last week and our next pour is planned for Friday 24 June, weather permitting. If we’re not able to complete the pour on Friday, we will defer the work to Monday 27 June.

    We need regular deliveries of concrete throughout the day, so there will be frequent truck movements to and from the facility.

    This means some of our deliveries will be outside our standard working hours on that day, including:

    • during school zone hours (between 8 am and 9:30 am and 2:30 pm and 4 pm)
    • between 6 am and 7 am in the morning

  • Relocating the cogeneration engine

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    We have two cogeneration engines at North Head that meet some of the facility’s energy needs. We capture biogas from the anaerobic digesters and use it to power a combustion engine that drives an electrical generator.

    On of our early activities on the project was to relocate one of the two cogeneration engines to allow room for the new digesters to be built.

    This involved:

    • demolishing the existing concrete slab
    • excavating and preparing the area to lay the new foundations
    • forming and pouring the new concrete slab and pavement
    • relocating the existing cogeneration engine and other associated equipment to the new location using a large crane
    • installing new electrical cables
    • upgrading the cogeneration engine to capture and reuse energy produced to heat the digesters.


    Check out our time lapse video showing the team in action here!


  • Crane delivery out-of-hours

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    We need to bring a large crane to site early in the morning when the roads are quiet, in line with Transport for NSW requirements.

    The crane will be delivered via Darley Road and Bluefish Drive on Thursday 24 February 2022, between 5 am and 6 am, weather permitting. At the end of the day, the crane will leave the site after hours between 7 pm and 8 pm.

    We’ll make every effort to minimise impacts on our neighbours during this delivery and avoid unnecessary loud noises, however the movement of the crane for this brief period will be noisy.


  • Construction has started!

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    The North Head biosolids upgrade project is now in progress. Funding for the project was approved in 2020 and since then, we’ve been working behind the scenes with our delivery partner, Confluence Water, on detailed designs and to prepare for construction.

    Construction will be delivered in two phases – phase one between late 2021 and the end of 2024, with the timing of phase two dependent on funding approval for future Sydney Water projects.

    As part of phase one, we’re building two new digesters and upgrading equipment to improve how we process biosolids at the North Head Water Resource Recovery Facility.

    All construction will take place within the existing North Head facility. Our neighbours in Manly won’t be able to see, smell or hear our work, but may notice more trucks moving equipment, people and materials at different stages of construction.



Page last updated: 08 Apr 2025, 10:58 AM