Intermittently decanted aerated lagoon (IDAL)
A pond or tank where wastewater undergoes several treatment processes in rotation, including sedimentation, biological treatment and clarification.
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Recycling water
Rouse Hill Water Resource Recovery Facility is one of about 30 water resource recovery facilities. It's Australia’s largest residential recycling scheme, and recycles water back to customers' homes for non-drinking purposes such as flushing toilets, watering gardens and washing cars.
Facts and figures
Location: Mile End Road, Rouse Hill
Population served: 32,000 properties
Area served: All or parts of Rouse Hill, Stanhope Gardens, Glenwood, Kellyville, Kellyville Ridge, Parklea, Acacia Gardens, Beaumont Hills, Quakers Hill, The Ponds and Castle Hill
Wastewater treated: 24 million litres each day
Treatment level: Tertiary
Recycled water applications: We reuse some water on-site for industrial purposes, like washing down equipment and backwashing filters. We supply up to 2 billion litres of recycled water a year to homes and businesses in the Rouse Hill area for non-drinking water uses. Learn more about water recycling and how you can use recycled water in your home.
Environmental discharge: We release excess recycled water to wetlands in Second Ponds Creek.
Biosolids produced: 10,000 tonnes each year
Operating licence and regulation: We operate the facility under 3 sets of rules.
- Environmental protection licence is issued by NSW Environmental Protection Authority (EPA).
- Recycled water the facility produces must meet the Australian Guidelines for Water Recycling.
- Biosolids the facility produces must meet the EPA's Environmental guidelines: Use and disposal of biosolids products.
Flow chart
Primary treatment
Primary treatment removes large solids using physical separation processes. Most of the solids removed can be treated for beneficial reuse.
Screening
Screens trap and remove large solids, such as paper, cotton buds and plastic, as wastewater flows through.
Grit removal
We stir the wastewater rapidly, forcing the water to spiral and create a vortex. The vortex causes grit to spiral to the centre of the tank, separating it from the water.
Large solids like wipes, food scraps, rubbish, cotton buds and plastic are caught on the screens.
Secondary treatment
Secondary treatment removes nutrients such as phosphorous and nitrogen using physical, biological and chemical processes. Learn more about Removing nutrients in wastewater.
We split the wastewater into 2 streams. One stream flows to the bioreactor and the other flows to the intermittently decanted aerated lagoons (IDALs).
Bioreactor
We add a high concentration of microorganisms (activated sludge) to the wastewater. By varying the amount of air in different parts of the tank, we ensure different types of microorganisms can break down nutrients like nitrogen and phosphorous.
We pump the wastewater to a clarifier. The activated sludge settles to the bottom of the clarifier where scrapers remove it. We recycle some of this sludge back into the bioreactor and treat the rest to produce biosolids.
The treated water from the top of the tank flows to tertiary treatment.
Microorganisms break down nutrients in the bioreactor.
IDAL
We add a high concentration of microorganisms (activated sludge) to the wastewater.
As in the bioreactor, varying the amount of air ensures different types of microorganisms are able to break down nutrients like nitrogen and phosphorous. In the IDAL, wastewater goes through 3 stages – aeration, settling and decanting – in one tank, rather than passing through separate tanks.
The IDAL goes through aeration, settling and decanting in one tank.
Tertiary treatment
Tertiary treatment uses chemical and physical processes to remove very fine solids and disinfect the treated wastewater.
Chemical mixing
We add chemicals that make the smallest particles stick together forming larger flocs. This process is called flocculation.
Tertiary clarifier
When the flocs become large enough they settle to the bottom of the clarifier and are removed.
The treated water flows from the top of the tank to the filters.
Filters
Filters made of layers of sand and coal trap and remove any remaining floc and fine solids.
Very fine particles are trapped and removed in the filters.
Disinfection
We use chlorine and ultraviolet light to kill any microorganisms that can make people sick.
Reusing the water
At our water resource recovery facilities, we use recycled water instead of drinking water wherever we can. Our hoses, sprays and filter backwashes all use recycled water. The remaining recycled water goes to local homes for reuse, or the local creek.
Residential recycled water
We supply up to 2 billion litres of recycled water to homes each year to flush toilets, water gardens, wash cars and for other outdoor uses.
Recycled water is supplied to customers through pipes that are separate from the drinking water supply. This is known as dual reticulation. Recycled water pipes and taps are coloured purple to distinguish them from the drinking water system.
Learn more about using recycled water.
Environmental flows
We release excess recycled water into artificial wetlands at Second Ponds Creek. It eventually flows into the Hawkesbury-Nepean River.
Homes in the Rouse Hill area can use recycled water on their gardens.
Operations and maintenance
Running the facility
Eight 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 take samples to monitor the facility's performance.
Maintenance type |
Description |
Example |
|---|---|---|
Preventative |
Prevents a breakdown |
Oiling a motor |
Planned |
Replacing equipment as it reaches the end of its useful life, before a breakdown |
Replacing a worn motor |
Reactive |
Fixing equipment that has unexpectedly broken down |
Repairing a motor |