Marine Environment

World-first major desalination field study finds there are no significant impacts on seawater quality or aquatic ecology from the operation of the desalination plant.

A world first, independent six-year study (Marine and Estuarine Monitoring Program) on the effects of the operation of Sydney Desalination Plant on local marine life was lead by the University of NSW (UNSW) with a team that included scientists from NSW Fisheries Research and Southern Cross University.

The comprehensive ecological study showed that the hyper-saline discharges from the plant have a minimal impact on the local marine environment.
It was a requirement of the project’s planning approval that there were no significant impacts on seawater quality or aquatic ecology from the seawater concentrate beyond the near field mixing zone and toxicity impacts within the near field mixing zone during operation were minimised.

Structures on the seabed off the Kurnell coast draw seawater into a tunnel and then into the plant. Seawater concentrate returns to the sea through another tunnel and then disperses via specially designed discharge nozzles.

The study took place at six underwater locations at depths of about 25 metres through periods when the plant was under construction, then operating and then idle. The multiple operating modes over the study’s lifetime enabled the analysis of operational impacts and recovery of marine life due to the hyper-saline discharges.

Study lead, Dr Graeme Clark said “The high-pressure diffusers that return the high-concentrate salt water to the ocean at a high velocity are so effective at diluting the brine that concentrations were almost at background levels within 100 metres of the outfall. This is the result of good engineering and good modelling behind the diffuser design. And within this small 100-metre impact zone, some invertebrates increased in numbers, the ones that benefit from high-flow conditions such as barnacles, and some were reduced in quantity or did not recover after shutdown of the outflow, and these were the species with slow swimming larvae, such as tubeworms, lace corals and sponges.”

More information on the study can be found here:

Marine and Estuarine Monitoring Program

Marine Water Quality and Ecosystem Environmental Management Plan

Beach and Foreshore Monitoring Program, Botany Bay Sector

Ecosystem Monitoring Program, Botany Bay Sector

Take a look at the seawater outlet during operation.