Intermittently Decanted Aerated Lagoons (IDAL)
A pond or tank where wastewater undergoes several treatment processes in rotation including sedimentation, biological treatment and clarification.
Rouse Hill Water Recycling Plant is one of our 30 wastewater treatment and water recycling plants. 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.
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.
Amount of wastewater treated: 24 million litres each day.
Treatment level: Tertiary.
Recycled water applications: We re-use 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.
Amount of biosolids produced: 10,000 tonnes each year
Operating licence and regulation: We operate the plant under 3 sets of rules:
– Read technical specifications for the plant.
(279 KB) – Learn about common wastewater parameters.
(192 KB) – fact sheet.
Treatment flow chart. Select the image to see a larger version.
Primary treatment removes large solids using physical separation processes. Most of the solids removed can be treated for beneficial re-use.
Screens trap and remove large solids, such as paper, cotton tips and plastic, as wastewater flows through.
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.
Secondary treatment removes nutrients such as phosphorous and nitrogen using physical, biological and chemical processes. Learn more about
We split the wastewater into 2 streams. One stream flows to the bioreactor and the other flows to the Intermittently Decanted Aerated Lagoons (IDAL).
We add a high concentration of micro-organisms (activated sludge) to the wastewater. By varying the amount of air in different parts of the tank, we ensure different types of micro-organisms are able to 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.
We add a high concentration of micro-organisms (activated sludge) to the wastewater.
Like in the bioreactor, varying the amount of air ensures different types of micro-organisms are able to break down nutrients (like nitrogen and phosphorous). In the IDAL, wastewater goes through three stages - aeration, settling and decanting - in one tank, rather than passing through separate tanks.
Tertiary treatment uses chemical and physical processes to remove very fine solids and disinfect the treated wastewater.
We add chemicals that make the smallest particles 'stick' together forming larger 'flocs'. This process is called flocculation.
When the flocs become large enough they settle to the bottom of the clarifer and are removed.
The treated water flows from the top of the tank to the filters.
Filters made of layers of sand and coal trap and remove any remaining floc and fine solids.
We use chlorine and ultraviolet light to kill any micro-organisms that can make us sick.
At our treatment plants, 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 re-use, or to the local creek.
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 to the drinking water supply, which 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.
We release excess recycled water into man-made wetlands at Second Ponds Creek, eventually flowing into the Hawkesbury–Nepean River.
Eight staff manage, operate and maintain the plant. They collect and analyse water samples, do laboratory testing and manage special projects to keep the plant running safely and efficiently.
There are 3 types of maintenance required to keep the plant operating: preventative, planned and reactive.
See the table below for examples.
Prevents a break down
Oiling a motor
Replacing equipment as it reaches the end of its useful life, before a break down
Replacing a worn motor
Fixing equipment that has unexpectedly broken down
Repairing a motor
Want to visit one of our sites? We offer free excursions and technical tours to schools, universities and community groups.