Treatment train

A treatment train is a sequence of multiple stormwater treatments which are designed to meet the needs of a particular environment, in order to maximise results.

When to use treatment trains

Treatment trains are important when a treatment measure needs pre-treatments to remove pollutants, such as nutrients and fine sediments, that would otherwise impact its performance.

For example, wetlands are designed to remove nutrients (e.g. fertilisers) and heavy metals from stormwater, but will perform poorly if gross pollutants (litter) and coarse sediments (gravel and sand) are not removed by a sediment pond upstream of the wetland.

Typical combinations

Select and order treatment measures appropriately to protect wetlands and raingardens from gross pollutants and coarse sediments.

The following illustrations show combinations of treatments, with arrows indicating the direction of stormwater flow.

Rainwater tanksRaingardens

Gross pollutant trapsSwales

Sediment pondsWetlands

Stages of the treatment train

Treatment​ Processes​ ​Pollutants Typical application​
Primary treatment​
  • physical screening
  • rapid sedimentation​
  • gross pollutants
  • coarse sediment​
  • grassed swales
  • litter traps
  • sediment ponds​
Secondary treatment​
  • fine particle sedimentation
  • filtration techniques​
  • fine sediment 
  • attached pollutants​
  • swales
  • infiltration trenches
  • porous paving
  • bio-retention systems
Tertiary treatment
  • enhanced sedimentation and filtration
  • biological uptake
  • absorption onto sediments​
  • nutrients
  • dissolved heavy metals​
  • bio-retention/ bio-infiltration systems and wetlands


Last updated:
6 November 2017