Bombo Water Resource Recovery Facility (WRRF)

Bombo WRRF is located on a 20.4 ha site in a former quarry on Bombo headland off Darien Avenue. The facility serves the townships of Kiama Heights, Kiama, Bombo, Kiama Downs, and Minnamurra. In 2005, flows from Jamberoo were transferred to the facility.

The facility was constructed in 1984 as a secondary wastewater treatment plant using intermittently decanted aeration lagoons (IDAL) as the secondary treatment facility. A cliff face underwater ocean outfall was constructed in 1984 to dispose of the treated wastewater to the South Pacific Ocean.

In 1993, two catch ponds were constructed to facilitate attenuation of decanted wastewater flows and to capture solids if sludge is carried over during the wastewater decant phase.

In March 2005, a new fourth IDAL, an extra step screen, grit tank and two additional sludge tanks were added.

The Bombo WRRF produces biosolids. This involves dewatering one of the facilities sludge lagoons, bringing in heavy machinery to deliver a mobile centrifuge used to create the biosolids, and load the end product into semi-trailers to remove from site. Currently 100% of the biosolids produced at our facility are beneficially re-used in agriculture, forestry, and land rehabilitation.

This activity happens every five to six months, with the next dewatering process to start in March 2024, taking about three weeks to finish. Unfortunately there may be intermittent odours during this time and we apologise for the inconvenience this may cause local residents, but we do appreciate your patience and understanding as we complete this work as quickly as possible.

Reporting Odour

If you’re experiencing odour issues you can let us know using a short online form or by clicking report odour. This is the quickest way to submit your experience and for us to respond.

Bombo Water Resource Recovery Facility (WRRF) on Bombo Headland

Bombo WRRF Update May 2024

We’ll soon be starting a series of construction projects to improve the operation of the Bombo Water Resource Recovery Facility (WRRF).

Chemical Dosing Unit

We will be installing a chemical dosing unit at the sludge lagoon. This unit will enable us to introduce magnesium hydroxide liquid (MHL) to our treatment process to address odours during sludge lagoon dewatering.

This specialised unit administers precise doses of MHL to effectively neutralize odours during the treatment process. The project will include storage tank, mixer, dosing pumps, valves, safety showers, and a bund for chemical deliveries. It will be automated and integrated into the plants existing control system. The magnesium hydroxide storage and dosing system will be sheltered under a carport type roof and contained in an existing concrete embankment. We’ll be doing some civil work to facilitate the installation of this unit which will include the building of a truck turning bay for the chemical truck.

Work is scheduled to begin in early May and will take up to seven months to complete, weather permitting.

Dewatering delayed and will now begin in May

At Bombo, we produce organic solids (sludge) during the wastewater treatment process. This sludge is collected and processed to convert it into a safe fertilizer product called biosolids. We use sludge lagoons to break down and stabilise the sludge. This makes nutrients available to plants and reduces pathogens and odour. Finally, we use a high-speed centrifuge to remove water from the biosolids (dewatering), making it easier to transport in trucks.

We previously let you know that dewatering will begin in April, however, due to wet weather, this work was delayed and will now commence in early May.

What you need to know

  • During dewatering, there may be a slight increase in odour for up to two days. To minimise the impact on our community, we’ll have odour neutralising spray system setup around the dewatering operations.
  • During construction, there will be an increase in noise and traffic, particularly along Darien Avenue, as contractors, delivery trucks and special equipment is required on site.

Where do I get more information and help?

If you would like to be kept informed about the project and receive updates via email and/or SMS, please provide us your details by clicking here

If you would like to know more, please contact our Community Engagement Team on 1800 006 113 (option 6) or email us at

Thank you for your cooperation during this essential work.

For those interested in the technical information:

  • Sludge - is the residue that accumulates in WRRFs. Sludge is the solid, semisolid, or slurry residual material that is produced as a by-product of treatment processes. With further biological treatment to reduce pathogens, odours and particles that attract insects and vermin, we produce biosolids.
  • Decanter centrifuge – separates solid materials from liquids in the slurry.
  • Boot – is the location where the solids settle.
  • Slurry – is a thin, sloppy, wet mixture of liquid and solid components that is a by-product of the treatment process.
  • IDAL – intermittently decanted aeration lagoon. Wastewater is collected in the IDAL tanks and pumped with air through diffusers. The air works with microorganisms in the tank to break down nitrates (nitrification) and organic matter.
  • Diffuser – is an aeration device used to transfer the air into the tank.
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