Case study: 99% blue green algae reduction at Wallan Lagoon 5

Wallan Sewage Treatment Plant operates with six treatment lagoons southeast of Wallan township. Lagoon 5 stores treated water from tertiary filters, and occasional overflow from Lagoon 3.

Yarra Valley Water aimed to improve Lagoon 5's water quality to potentially feed their planned Class A Recycled Water Treatment Plant.

Traditional algae control methods using aeration systems were proving both expensive to maintain and ineffective at controlling blue-green algae blooms. They needed a solution that would reliably improve water quality while reducing operational costs and maintenance requirements.

So, in late November 2022, ahead of the summer peak algae season, EnviroSonic ultrasound units were installed in Lagoon 5. Yarra Valley Water was convinced because, unlike chemical treatments or mechanical solutions, our environmentally friendly approach requires no chemicals, operates silently, and needs minimal maintenance, making it ideal for long-term water quality management.

Testing just 4 months later in March 2023 showed impressive results:

• Synechocystis showed over 99% lower concentration in the untreated lagoon: (31k cells/mL in Lagoon 5 vs. 3.5M cells/mL in Lagoon 6)

• Multiple harmful algae species completely eliminated in the treated lagoon, including Geosmin-MIB producing BGA, Cyanobacterial Filaments, Merismopedia and Monoraphidium

• Suspended solids were significantly reduced in the treated lagoon - with an 81% reduction compared to the untreated lagoon

With further incredible benefits for Yarra Valley Water overall:

• 19× lower costs to maintain than aerators, including significant labour cost savings from fewer filter blockages and cleaning frequency.

• No chemicals

• No noise

• Improved water clarity