Microorganisms
Organisms that are too small to be seen without a microscope.
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Recycling water
St Marys Water Resource Recovery Facility is one of about 30 water resource recovery facilities in Greater Sydney. We treat wastewater to tertiary standard. We use the recycled water for onsite reuse, irrigating a local golf course and environmental flows.
Facts and figures
Location: Links Road, St Marys
Population served: 160,000 people
Area served: 84 square kilometres, including the suburbs of Cambridge Park, Werrington Downs, Blackett, Mount Druitt, Minchinbury and St Clair
Amount of wastewater treated: 33.5 million litres each day
Treatment level: Tertiary
Recycled water applications: We reuse some water on-site for industrial purposes like washing down equipment and filter backwashes. Dunheved Golf Course uses our recycled water. They use up to 2 million litres a day to water the greens.
Environmental discharge: We release 4–8 million litres a day to a tributary of South Creek. We send the remainder to the St Marys Advanced Water Treatment Plant for advanced treatment before we release it to the Nepean River.
Biosolids produced: 20,000 tonnes each year
Operating licence and regulation: We operate the plant under 3 sets of rules.
- Environmental protection licence issued by NSW Environmental Protection Authority (EPA) – find out more about our EPA licences and limits.
- 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 wastewater 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 as wastewater flows through.
Grit removal
We inject air into a tank, causing the water to spiral. The air flings the grit, such as sand and coffee grounds, to the edges. It collects in the bottom of the tank, where a scraper removes it.
Large solids like wipes, food scraps, rubbish, cotton buds and plastic are caught on the screens.
Sedimentation
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.
We use scrapers on the sedimentation tank to remove floating scum and settled solids.
Secondary treatment
Secondary treatment removes nutrients such as phosphorous and nitrogen using physical, biological and chemical processes. Learn more about Removing nutrients in wastewater.
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.
The bioreactor has different aeration zones.
Secondary 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 use clarifiers to separate the activated sludge from the treated wastewater.
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 flocs. This process is called flocculation.
Large paddles stir chemicals into the water to help remove tiny particles.
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.
Filtration
Filters made of layers of sand and coal trap and remove any remaining floc and fine solids.
Disinfection
We add chlorine to kill any microorganisms. We remove any residual chlorine before discharging the treated wastewater to the environment or recycling it.
Flocs settle to the bottom of the tertiary clarifier.
Reusing the water
On our plants, we use recycled water instead of drinking water wherever we can. Hoses, sprays and filter backwashes all use recycled water. We use the remaining recycled water in a few ways.
Local golf course
We supply the local golf course with as much recycled water as it needs to irrigate the greens and fairways.
Environmental flow
We release some water into the local creek, a tributary of South Creek, to help keep it alive and healthy.
Advanced treatment
The rest of the water is sent to the St Marys Advanced Water Treatment Plant for further treatment using membrane technology. This water is released into the Hawkesbury-Nepean River for environmental flow.
Dunheved Golf Course uses recycled water instead of drinking water to irrigate the greens.
We release high-quality recycled water for environmental flow at Penrith.
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 the plant 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 monitor the facility to make sure it's working at its best.
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 |