Risdon Brook Dam

Your sewage

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.

Sewage do and do nots

Disposing certain liquids down the sink can damage the sewerage system and make your wastewater difficult to treat, potentially causing harm to the environment. You can help to keep the cost of sewage treatment down by being careful about what you put down the drain.

What you can do to help us look after your sewerage systems:

Do:

  • Use a sink strainer in your sink and empty the contents into a rubbish bin or your compost. Sink strainers reduce the load on our treatment systems. Similarly, sink waste disposal systems also increase the organic load on our treatment plants
  • Use the Local Government Association of Tasmania’s sponsored chemical collection services rather than dispose of unwanted household chemicals and medicines down the sink
  • Recycle old paint – give to your local tip shop
  • Dry out leftover paint in the tin and put it in the rubbish – use sawdust or newspaper to help absorb the liquid
  • Wash paint brushes on the lawn rather than in a sink.

Do not:

  • Put cooking oil down the sink – recycle it instead. Oil recyclers will take old oil for free and convert it into biodiesel, animal feed and other useful products. You can also mix cooled cooking oil in with your compost and it will break down organically
  • Put paint or other chemicals down the sink.

If a blockage occurs on your property, contact your local licensed plumber for assistance.