How septic systems work | City of Casey
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How septic systems work

Septic systems consist of 3 distinct components:

  • Inlet drains which transfer wastewater from your house to the septic system.
  • The wastewater is then treated by bacterial action within the septic system, and solids are removed from the waste.
  • A disposal system disposes of treated liquid waste from the septic tank within your property, usually via subsoil absorption or surface/sub surface irrigation. Buildings, vehicles or livestock cannot impede on this disposal area.

Types of septic systems

In Casey, the most common domestic on-site wastewater management systems (septic systems) are:

  • conventional septic tanks
  • mechanical treatment plants

Conventional septic tank system

A conventional septic tank system (or primary system) is made up of a septic tank and a series of soil absorption and/or transpiration trenches. All wastewater enters the septic tank. The solids settle to the bottom and are retained in the tank, forming a sludge layer, while fats and greases collect at the top known as a crust.

Mechanical treatment plant system

A mechanical treatment plant consists of a large tank with several treatment compartments:

  • the first is like a septic tank
  • the second mixes air with the wastewater to assist bacteria to break down solids
  • the third allows for settling of solids
  • the last disinfects through chlorination or UV saturation

Wastewater from treatment plants is of higher quality than conventional septic tank systems. It is disposed through absorption and/or transpiration trenches, surface and sub surface irrigation.

Sand Filter Septic System

A sand filter system consists of a large, generally subsurface structure filled with sand. Effluent from the septic tank percollates through the sand in the sand filter and captures any remaining solid material. This provides a good environment for bacteria to digest wastewater and reduce pollution. Once treated in the sand filter, the effluent is disposed into underground trenches, or sub-surface irrigation systems or another approved method. Sand filter systems are an extremely effective method for reducing risks to the environment and for increasing wastewater disposal options.

More information

  • If you are considering purchasing a new septic system, our fact sheet Septics and Wastewater Treatment Systems¬†will help you to select the right type for your property and to get approval from us.