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Treatment systems

Treatment systems for improving water quality are engineered and designed to intercept, slow down and remove pollutants from surface or groundwater. This is different from wetland rehabilitation. Pollutants such as sediments, nutrients and other toxicants (pesticides, heavy metals etc.) generated from urban, industrial and agricultural land uses, can degrade the condition and function of wetlands and coastal or marine environments. Improving water quality, from catchment land uses, is essential to maintain or improve the health and resilience of these ecosystems. Treatment systems, when used in conjunction with best practice land management, can improve water quality on a catchment scale.

Newly planted constructed wetland Photo by Queensland Government

Quick facts

treatment systems can be effective in reducing the concentration of pollutants such as sediment, nutrients and pesticides from diffuse sources[1].

Click on treatment systems in the diagram above for additional information.


Treatment systems are designed to enhance natural hydrologic, physical, biological or chemical processes and components (parts of the system e.g. soil, vegetation etc.) to remove specific pollutants from water (Table 1). No single treatment system is efficient in treating all pollutants. That is why multiple treatment systems are often combined to form a treatment train.

Treatment systems complement, but do not replace the need for measures to prevent the loss of pollutants from the source, such as erosion control (e.g. pile fields, ground cover) or remove the need to implement nutrient, sediment, chemical and water best management practices. Best management practices are the essential first step in any treatment train to prevent or minimise pollutants entering the water system.

The treatment system or treatment train must be designed for the quantity and quality of water entering the system. Quantities of sediments, nutrients or other toxicants above the design criteria will overload and in many cases damage treatment systems, causing them to stop working effectively and potentially lead to costly maintenance and repair. Likewise, directing relatively clean water, such as runoff from undeveloped land, away from treatment systems leads to a more effective treatment system by ensuring that only the water requiring treatment enters the treatment system.

Treatment systems can be used at a range of scales from house block or paddock scale, through to regional scale systems treating runoff from multiple properties or a whole catchment. The type, design and operation of a treatment system and treatment train depends on a number of factors including:

  • the location in the landscape and the catchment characteristics including:
    • hydrological regime e.g. wet and dry seasons, runoff, natural wetland systems, waterway connectivity
    • soils
    • groundwater
  • land use (agriculture, urban, industrial or intensive)
  • the values in the receiving environment
  • existing management practices to reduce pollutants
  • the nature of the pollutant and volume of water to be treated
  • the level of treatment required
  • other treatment systems in the treatment train
  • costs including construction, operating, maintenance and monitoring
  • the degree of acceptance and potential impacts on the community.


Click on the links below for information on the design and operation of treatment systems for different land uses:

This information is specifically for treatment systems designed for pollutant removal. If the primary objective of the system is to provide habitat or other ecosystem services, see the wetland rehabilitation page.

Table 1: Treatment processes used in treatment systems to remove different types of pollutants[2][3][4][5][6]
Pollutant Size / Type Process category Treatment processes
Minimise runoff volume Hydraulic





Coarse pollutants (>125μm) Physical Sedimentation
Fine sediments (<125μm) and particulate nutrients



Enhanced sedimentation




Dissolved nutrients, pesticides and other toxicants



Plant absorption / uptake

Nitrification / denitrification

Microbial degradation







In addition to the standard disclaimer located at the bottom of the page, please note the content presented is based on published knowledge of treatment systems. Many of the treatment systems described have not been trialled in different regions or land uses in Queensland. If you have any additional information on treatment systems or suggestions for additional technologies contact us via the feedback link at the bottom of the page.

Additional information

Using denitrifying bioreactors to improve water quality on Queensland farms

Constructed wetlands for pollution control: processes, performance, design and operation

Melbourne Water—Constructed wetlands

Minnesota Pollution Control Agency—Processes for removing pollutants from stormwater runoff

Water Environment Research Foundation—Critical assessment of stormwater treatment and control selection treatment

A model for urban stormwater improvement conceptualization. Global Solutions for Urban Drainage

Bakers Creek Treatment Train - drone footage

Building a Bioreactor Bed in the Wet Tropics

Pages under this section


  1. ^ Eberhard, R, Thorburn, P, Rolfe, J, Taylor, B, Ronan, M, Weber, T, Flint, N, Kroon, F, Brodie, J, Waterhouse, J, Silburn, M, Bartley, R, Davis, A, Wilkinson, S, Lewis, S, Star, M, Poggio, M, Windle, J, Marshall, N, Hill, R, Maclean, K, Lyons, P, Robinson, C, Adame, F, Selles, A, Griffiths, M, Gunn, J & McCosker, K (2017), Scientific Consensus Statement 2017: A synthesis of the science of land-based water quality impacts on the Great Barrier Reef, Chapter 4: Management options and their effectiveness.. [online], State of Queensland, Queensland. Available at:
  2. ^ Kadlec, RH, Knight, RL, Vymazal, J, Brix, H, Cooper, P & Haberl, R (2000), Constructed wetlands for pollution control: processes, performance, design and operation, IWA Publishing, London.
  3. ^ Melbourne Water (28 September 2017), Constructed wetlands. [online], Melbourne Water. Available at: [Accessed 27 February 2018].
  4. ^ Minnesota Pollution Control Agency (14 July 2017), Processes for removing pollutants from stormwater runoff. [online], Minnesota Pollution Control Agency. Available at: [Accessed 29 July 2018].
  5. ^ Strecker, E (2006), Critical assessment of stormwater treatment and control selection treatment., Water Environment Research Foundation, Alexandria.
  6. ^ Wong, T, Fletcher, T, Duncan, H, Coleman, J & Jenkins, G (2002), 'A model for urban stormwater improvement conceptualization', Global Solutions for Urban Drainage, pp. 8-13.

Last updated: 5 October 2018

This page should be cited as:

Department of Environment and Science, Queensland (2018) Treatment systems, WetlandInfo website, accessed 13 May 2021. Available at:

Queensland Government
WetlandInfo   —   Department of Environment and Science