Recycled water is treated differently to drinking water to ensure it is a safe and reliable alternative water supply.
How recycled water is treated
Wastewater is transferred through the sewerage network to a recycled water plant, where it is treated in three stages.
Primary stage
During the primary stage, solids are removed. The water passes through a screen, which prevents large objects such as bottles and plastic bags from entering the system. Water then passes into a tank, where remaining solids sink to the bottom and are removed.
Secondary stage
In the secondary stage, the liquid moves into large aeration tanks where oxygen is pumped in to encourage the growth of micro-organisms. These break down organic matter into simple materials such as water and carbon dioxide. A floating sludge separates from the water during this process and is sent to a sludge digester, where it takes around 15 days to break down. The remaining liquid from the secondary tanks is moved to stabilising tanks, where remaining solids settle to the bottom.
Tertiary stage
Phosphorous is removed during the tertiary stage. Phosphorous is a chemical that is often added to detergents, but which is harmful to the environment. Sewage is filtered one last time and remaining solids (biosolids) are removed. The remaining water is disinfected with chlorine. This purified water is then pumped into a shallow holding tank, where sunlight penetrates the water to kill remaining bacteria. Once this process is complete, the water is recycled or discharged into the environment.
