New technologies – Phosphorus-binding clay trials
Water treatment techniques to reduce algal blooms in the short term may be an option to provide respite to estuarine health while longer nutrient reduction activities in the catchment are realised. Healthy Estuaries WA is investigating the effectiveness of a newly developed clay that binds phosphorus making it unavailable for algae growth.
Read more about trials that have occurred since 2016:
- Cox Bay North Lake - February and March 2024, November 2024 to February 2025
- Gull Road Drain - September 2023
- Lower Serpentine River - March 2020
- Punrak Drain - 2017
- Lower Vasse River - 2016-2018
The trials being undertaken in the Lower Vasse River are also part of Revitalising Geographe Waterways.
How does the clay work?
The clay being trialled consists of a naturally occurring clay that is modified with a mineral coating that binds phosphorus.
It reduces algal growth by removing phosphorus in the water while making it unavailable to algae. It also forms a protective layer on the sediments, preventing phosphorus release.
The trials provide information to help with further research and clay development, including:
- improving the clay manufacturing process;
- best application rates for different environments; and
- undertaking a detailed risk assessment for large-scale clay application.
We hope to demonstrate the benefits of the clay for drain treatment in the Peel-Harvey catchment and treatment of standing water bodies such as the Lower Vasse River to enable a widespread application.
Cox Bay North Lake
The Department of Water and Environmental Regulation is conducting water quality treatment trials at Cox Bay North Lake in Mandurah.
The first trial was completed between February and May 2024.
We are currently conducting another trial from November 2024 to February 2025.
Gull Road Drain
Gull Road Drain is part of the lower Serpentine catchment, a tributary to Bindjareb Djilba (the Peel-Harvey estuary). The drain is located approximately ten kilometres east of Mandurah. It flows westward through agricultural land, generally from late winter to spring and transports excess nutrients into Yalbanberup Pool and the Waangaamaap Bilya (Serpentine River).
During the trial, we diluted approximately 22 tonnes of HT-clay into a slurry and added it to the drain continuously using a metered hose with a spray nozzle fitting. We measured the water quality in Gull Road Drain on a weekly basis before and after the trial, and more intensively during the trial.
Lower Serpentine River
The Serpentine River, which flows into the Peel-Harvey Estuary carries high levels of nutrients. We conducted a water treatment trial in the Lower Serpentine River in March 2020.
Punrak Drain trial
In October 2017, the clay was trialled at Punrak Drain.
It was the first time that the clay was applied at such a large scale in a fast flowing agricultural drain.
Over 500 kilograms of the clay was applied into the flowing water over five hours. The water was monitored for phosphorus and other water quality indicators such as turbidity, nitrogen, pH, suspended solid content or dissolved oxygen before, during and after the application.
The results of this trial will help us understand best application rates, efficiency of treatment, how the clay moves through the drain and where it settles.
Results of the trial are now available.
Lower Vasse River trials
As part of the Revitalising Geographe Waterways, a trial on the Lower Vasse River during the summer of 2016-2017 showed promising results.
Fifteen large bottomless tanks, or mesocosms were placed in the river near the Lower Vasse traffic bridge. The clay-treated mesocosms showed reduced algae growth and improved water quality. This was evident both visually and when tested for algal growth indicators.
The next large-scale trial using the newly developed clay took place in the Lower Vasse River over the summer of 2017-2018. View media statement here.
The clay was applied to two 15 by 30 metre areas where different application times and amounts were tested.
Results of both trials are now available.
