Project Details

WSUD Category: Wetland/lake algae management

Development Type: Public Open Space
Function/Driver: Water quality
Government Area: City of Mandurah
Year Completed: 2019

 

Type of wetland

Constructed – Urbanised

Wetland management issue

  • The waterbody has a natural groundwater connection due to the low groundwater table. The lake is not supplied with any further groundwater via a bore system.
  • The waterbody has a disconnected drainage network with stormwater only entering the lake on big rainfall events via one bubble-up storm water outlet.
  • The waterbody receives stormwater from residential areas and parks runoff.
  • The waterbody is supplied with oxygen and mixing via five aerator diffusers run by solar power.
  • The water quality experiences ongoing sources of nutrients and is continuously eutrophic with high levels of phosphorus.

Treatment trialed

  • Name of treatment: Phoslock
  • Quantity used: 2,000 kg
  • Method of application: Mobile shore-based application equipment.
  • Is there any known scientific research supporting its effectiveness? Yes. Proposal for Phoslock treatment of Lyndhurst Place Lake Mandurah, Report, Phoslock Environmental Technologies.

Date(s) of treatment

27/05/2019 one-off application

Outcome of treatment

  • Visual observations: Water column seems clearer.
  • Have water parameters specific to the treatment claims been measured before and after application?  Yes. “Cox Bay North Lake Quarterly Health Check Report, EcoAdvise, August 2019″ (available upon request).
  • Water testing was carried out on the 12/06/2019 after the first major winter rainfall event. Further regular quarterly testing was carried out on the 8/08/2019.
  • Phoslock treatment reduced the TP concentration in the water considerably, by 73% after two weeks and by 94% after three months. Also, Phoslock treatment has helped to drop the EC or TDS levels in water and showed a 71% reduction in Biochemical Oxygen Demand (BOD) levels after 3 months, which would help to maintain the dissolved oxygen levels in the water.
  • Although the TP level dropped post Phoslock treatment, TN and TP levels remained high enough for the lake to be considered eutrophic.

 

Contact Officer:  Tanith McCaw and Dale Robinson

Email: [email protected] and [email protected]

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