The used water that goes down toilets, sinks and drains and into the sewerage system. Also known as sewage. About 99% of it is water.
Penrith Water Recycling Plant is one of 30 wastewater treatment and water recycling plants in Greater Sydney. We treat wastewater to tertiary standard and use the recycled water for on-site re-use and environmental flows, and to water local sporting fields.
Population served: 100,000 people.
Area serviced: 63 km2, including the suburbs of Castlereagh, Cranebrook, Mt Pleasant, Penrith, Glenmore Park, Glenbrook, Blaxland, Warrimoo and Mt Riverview.
Amount of wastewater treated: 24 million litres each day.
Treatment level: Tertiary.
Recycled water: We re-use some water on site for industrial purposes like washing down equipment and filter backwashes. Penrith Council uses up to 18 million litres of our recycled water a year to water nearby sports fields.
Environmental discharge: We send the remainder to the St Marys Advanced Water Recycling Plant for advanced treatment. The water is returned to Penrith and released into Boundary Creek. It flows to the Nepean River.
Amount of biosolids produced: 20,000 tonnes each day.
Operating licence and regulation: We operate the plant under 3 sets of rules:
– read technical specifications for the plant.
(279KB) – learn about common wastewater parameters.
(192KB) – fact sheet.
Primary wastewater 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 as wastewater flows through.
We stir the wastewater rapidly, forcing the water to spiral and create a vortex. The vortex causes grit, like sand and gravel to spiral to the centre of the tank, separating it from the water.
We split the wastewater into two streams. One stream flows to the sedimentation tank and bioreactor and the other flows to the Intermittently Decanted Aerated Lagoons (IDAL).
Sedimentation tanks allow solids to settle to the bottom of the tank while oil and grease float to the top. Scrapers at both the bottom and the top of the tanks remove the solids, oil and grease, which are then treated to produce biosolids.
Secondary treatment removes nutrients such as phosphorous and nitrogen using physical, biological and chemical processes. Learn more about(192KB).
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 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 microorganisms can 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.
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.
Filters made of sand trap remove any remaining floc and fine solids.
For disinfection we add chlorine to kill any microorganisms that can make us sick. We remove any residual chlorine before discharging the treated wastewater to the environment or recycling it.
We use the recycled water in a few different ways.
A small team 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 three 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
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