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Algae treatment

Algae treatment — Planning and design

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Figure 3 Large scale HRAP ponds. Photo by Pacific Biotechnologies Australia

Site selection

Preferably within local catchment areas in the scale of 1000 Ha or greater.

Access to power source for pumps and harvesting.

Needs to be out of flood prone areas where the ponds may be inundated or in some way protected from floods.

Needs full sun for the algae to grow, so suits sites without shade from building or trees.

Located where the system will have access to regular water flow.

These systems are designed for continuous operational wastewater flows rather than unpredictable environmental flows. They have been operated over multiple wet and dry seasons with quantified variation in productivity. There is limited capacity to manage flood events and heavy sediment loads.


Approximately 0.16-0.4% of catchment area is required[3][1].


  • HRAP's are typically shallow (30-50cm deep)[2], oblong ponds with a raceway shape. They are often configured as a single loop. Ponds are constructed above-ground using concrete, steel, fibreglass or poly/plastic (Figure 3) or in-ground using water-tight membranes or polyethylene liners in ponds excavated in the earth. They have vertical or battered edges.
  • If the influent water contains suspended solids the system requires a sand filter or sediment basin to filter sediment prior to entering the HRAP.
  • HRAP require an inlet from the sand filter or sediment basin to the HRAP to regulate flows into the system and an outlet with a structure enabling the algae to be harvested.
  • A mechanical mixer, such as a low-energy paddle wheel is required near the inlet to circulate the algae to maximise access to sunlight to encourage growth and nutrient uptake. The mixer also minimises stratification and the sunlight can help breakdown pathogens and potentially pesticides[2].
  • Needs to be lined to prevent water loss to groundwater.

Figure 4 Typical design of a single loop high rate algal pond. Image by South Australian Local Government Association, 2020


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. The information will be updated as new trials are conducted and monitored. If you have any additional information on treatment systems or suggestions for additional technologies please contact us using the feedback link at the bottom of this page.


  1. ^ Lawson, A (8 July 2016), 'Bioremediation using freshwater algae', Treatment Systems in Coastal Catchments Forum. [online] Available at:
  2. ^ a b Local Government Association of South Australia (June 2020), High Rate Algal Pond (HRAP) Design Guideline.pdf. [online] Available at:
  3. ^ Rickert, A & McShane, T (2015), Remediation of Agricultural Irrigation Runoff Using High Rate Algal Ponds: A feasibility study. [online], Burdekin-Bowen Integrated Floodplain Management Advisory Committee (BBIFMAC). Available at:

Last updated: 10 June 2022

This page should be cited as:

Department of Environment, Science and Innovation, Queensland (2022) Algae treatment — Planning and design, WetlandInfo website, accessed 18 March 2024. Available at:

Queensland Government
WetlandInfo   —   Department of Environment, Science and Innovation