How the sewerage system works
Ordinary household sewage comes into the system from drains in our homes before entering the vast collection of underground sewer pipes.
The toilet, kitchen, bathroom and laundry waste leave the house through a private sewer pipe line, before connecting up to a network of underground sewers and pump stations which TasWater maintains and operates.
Sewage can take many hours to travel through the sewerage network before reaching a sewage treatment plant for processing. At the sewage treatment plant, sewage can be treated in three stages: primary, secondary and tertiary.
Primary treatment
Sewage treatment plants can achieve primary treatment in a number of ways. The first stage of the treatment is generally a coarse screen to remove objects that should not be in sewage.
This is generally followed by grit removal and primary settling so solids can settle and grease can be skimmed from the surface.
Secondary treatment
Following primary treatment, biological (secondary) treatment assists the removal of contaminants and bacteria. This is generally achieved through the use of micro organisms which consume organic matter.
Secondary level treatment plants also involve disinfection of effluent prior to discharge or release for reuse.
Tertiary treatment
Tertiary treatment is used where the removal of specific wastewater contaminants such as nitrogen and phosphate is required.
Tertiary treatment occurs when removal at greater levels than can be achieved by secondary treatment is required.
After treatment, the treated wastewater is returned to the environment. In a number of instances, TasWater is able to recycle the treated water and biosolids from treatment plants for suitable farming applications.