Aeration tanks (bioreactors)

The active biomass harnesses bacteria to remove nitrogen,
phosphorus and carbon from the sewage via the three zones
within the aeration tanks. The phosphorus can also be
removed chemically by alum or ferric dosing. Alum and ferric
chemically bind phosphorus allowing it to be removed in the
clarifier and biosolids process.

Note for budding scientists

The three zones within the aeration tanks do the following tasks:
1. Aerobic zone: Nitrifers convert ammonia to nitrate which
promotes biological phosphorus uptake in a process
called nitrification.
2. Anoxic zone: Nitrate is converted to nitrogen gas that
is released to the atmosphere in a process called
3. Anaerobic zone: A vital zone for one step in the biological phosphorus uptake process.


The City is responsible for monitoring the entire sewage
treatment process from beginning to end to ensure every stage is functioning as required. We have adopted a HACCP (Hazard Analysis Critical Control Point) certified risk management system which identifies monitoring needs at each stage of treatment for the early detection of system malfunctions.

Additionally, we monitor effluent and recycled water quality
to meet strict standards issued by the Department of
Environment and Heritage Protection in order to supply
recycled water to our customers and to release excess
recycled water to our ocean. Parameters which are
monitored against these standards include BOD (biological
oxygen demand), suspended solids, pH, dissolved oxygen,
chlorine, nutrients and bacteria. Annual quality data is
available on our website.

Glossary of terms